Acute Variables: Training Frequency and Recovery Between Sessions

WITS

TPTA

ACSM

NYPT

Acute Variables: Training Frequency

This course discusses how many sessions per week per <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> group is ideal, and how many days rest between sessions is ideal. Further, this course discusses the variables that do and do not influence frequency and recovery time. Detailed recommendations are discussed for novice exercisers, experienced exercisers, adolescents, adults, and older exercisers. Additionally, the course discusses recommendations based on training goals (body fat loss, hypertrophy, strength, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, sports performance, etc.).
Some findings from the included systematic review resulted in counterintuitive findings. For example, during resistance training, increased load, but not increased velocity (<a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training), significantly increased post-exercise decreases in strength, increases in delayed onset <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> soreness (DOMS), and increases in recovery time. Additionally, research implies that the most dramatic improvements in recovery are between the 1st and 2nd sessions of a new routine, regardless of gender, age, or training experience.
Movement professionals (personal trainers, fitness instructors, physical therapists, athletic trainers, massage therapists, chiropractors, occupational therapists, etc.) should consider acute variables essential knowledge for <a id="optimal" data-tip="1571" target="_blank" href="/glossary-term/optimal" class="glossary">optimal</a> exercise programming, and sets/muscle group/session is one of those acute variables. This course is part of our continued effort to optimize &#x201C;acute variable&#x201D; recommendations.
<h3>Additional Courses:</h3>
<ul>
 <li><a href="https://brookbushinstitute.com/courses/acute-variables-repetition-tempo">Acute Variables: Repetition Tempo</a></li>
 <li><a href="https://brookbushinstitute.com/courses/acute-variables-repetition-range">Acute Variables: Repetition Range</a></li>
 <li><a href="https://brookbushinstitute.com/courses/acute-variables-rest-between-sets" target="_blank" rel="noopener">Acute Variables: Rest Between Sets</a></li>
 <li><a href="https://brookbushinstitute.com/courses/acute-variables-sets-per-muscle-group" title="Sets Per &lt;a id=" muscle-cell" data-tip="1781" target="_blank" class="glossary">Muscle</a> Group&quot; target=&quot;_blank&quot; rel=&quot;noopener&quot;&gt;Acute Variables: Sets Per <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">Muscle</a> Group</li>
 <li><a href="https://brookbushinstitute.com/courses/acute-variables-circuit-training">Acute Variables: Circuit Training</a></li>
 <li><a href="https://brookbushinstitute.com/courses/acute-variables-training-frequency-and-recovery-between-sessions" title="Training Frequency" target="_blank" rel="noopener">Acute Variables: Training Frequency</a></li>
</ul>

<h3><span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Position Statement</h3>
<ul>
 <li>Training frequency and recovery between sessions should be based on the ability to achieve the same or better performance in subsequent sessions. Generally, more days rest should be given between initial sessions of a new routine and then increased to 2-3x/muscle group/week. For experienced exercisers, research suggests that it may not be possible to perform <a id="optimal" data-tip="1571" target="_blank" href="/glossary-term/optimal" class="glossary">optimal</a> volume and intensity with a frequency of 1 or fewer sessions/muscle group/week; 2 and 3 sessions/week result in similar improvements, and 4 sessions/muscle groups/week may result in less improvement (due to targeting similar <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> groups on consecutive days). In summary, the most efficient and effective recommendation may be a frequency of 2 sessions/muscle group/week, with 2-3 days rest between sessions. However, during the initial sessions of a new routine, 3 sessions/muscle group/2 weeks with 3-7 days rest may be recommended.</li>
</ul>
<ul></ul>
&#xA0;
<h3><span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Recommendations:</h3>
<ul>
 <li>General recommendation: 2-3 sessions/muscle group/week and 2-5 days rest between sessions</li>
 <li>Starting a new routine: 3 sessions/muscle group/2 weeks and 3 - 7 days rest between sessions
 <ul>
 <li>Alternatively: Consider scheduling &quot;de-loading weeks&quot; after the first session of a new routine (not the last session of a routine).</li>
 </ul>
 </li>
 <li>The primary indicator of sufficient recovery: Set performance, including set intensity (load or velocity), set volume (reps and time-under-tension), or total work/sets (reps x load x sets).</li>
 <li>Additional Recommendations:
 <ul>
 <li>Initial Training Period (8-12 weeks): 1 - 3 sessions/muscle group/week</li>
 <li>Maintenance: 1-2 sessions/muscle group/week</li>
 <li>Body Composition: 3 or more sessions/week</li>
 <li>High-volume (Advanced) Training: 4 or more resistance training sessions/week necessitate split routines.</li>
 </ul>
 </li>
</ul>
<ul></ul>

<img alt="This graph compares an approximated average recovery following 1st and 2nd sessions of resistance training, depicting the dramatic difference in values." title="Post-exercise Recovery" src="https://www.datocms-assets.com/25800/1687791968-session-recovery.png">
<h2>Sample Program:</h2>
<h3>Experienced Exerciser:</h3>
<ul>
 <li>Goal: Hypertrophy</li>
 <li>Split: Upper and Lower</li>
 <li>Routine Construction: Strength/Stability Super-sets and Circuit Training</li>
</ul>
Acute Variables:
<ul>
 <li>Load: Moderate (75-90% of 1-RM); Lighter (60-75% of 1-RM)</li>
 <li>Reps/set: 6-12 reps; 6-12 reps</li>
 <li>Sets/exercise (circuits): 2-3 sets/<a id="muscle-cell" data-tip="1781" target="_blank" href="https://brookbushinstitute.com/glossary-term/muscle-cell" class="glossary" rel="noopener">muscle</a>&#xA0;group</li>
 <li>Rest between exercises: Circuit training, 1 min rest between exercises</li>
 <li>Training Time:&#xA0;25 &#x2013; 45 minutes (excluding warm-up).</li>
</ul>
Schedule:
<ul>
 <li>Week 1 and 2 (3x/routine/2 weeks):
 <ul>
 <li>Upper Body: Monday, Friday, and the following Wednesday</li>
 <li>Lower Body: Wednesday, the following Monday, and Friday&#xA0;</li>
 </ul>
 </li>
 <li>Weeks 3 and 4-6: (2x/routine/week)
 <ul>
 <li>Upper Body: Monday, Thursday</li>
 <li>Lower Body: Tuesday, Friday</li>
 </ul>
 </li>
</ul>
Upper Body Routine:
<ul>
 <li>Chest:
 <ul>
 <li><a href="https://brookbushinstitute.com/videos/bench-press-chest-press" target="_blank" rel="noopener">Incline Bench Press</a></li>
 <li><a href="https://brookbushinstitute.com/videos/asymmetrical-chest-press" target="_blank" rel="noopener">Asymmetrical dumbbell press on ball</a></li>
 </ul>
 </li>
 <li>Back:
 <ul>
 <li><a href="https://brookbushinstitute.com/videos/pull-ups-and-progressions" target="_blank" rel="noopener">Pull-up</a></li>
 <li><a href="https://brookbushinstitute.com/videos/suspension-row-and-progressions" target="_blank" rel="noopener">Unilateral suspension row</a></li>
 </ul>
 </li>
 <li>Shoulders:
 <ul>
 <li><a href="https://brookbushinstitute.com/videos/overhead-press" target="_blank" rel="noopener">Curl-to Press</a></li>
 <li><a href="https://brookbushinstitute.com/videos/single-leg-alternating-horizontal-abduction-with-external-rotation" target="_blank" rel="noopener">Single-leg alternating horizontal abduction</a></li>
 </ul>
 </li>
</ul>
Lower Body Routine:
<ul>
 <li><span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Integrated Exercise: 
 <ul>
 <li><a href="https://brookbushinstitute.com/videos/dynamic-lunge-with-chest-press-aos-progressions" target="_blank" rel="noopener" style="letter-spacing: 0px;">Transverse plane lunge to </a><a id="unilateral" data-tip="1551" target="_blank" href="/glossary-term/unilateral" class="glossary">unilateral</a> chest press</li>
 </ul>
 </li>
 <li><span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Legs:
 <ul>
 <li><span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;"><a href="https://brookbushinstitute.com/videos/deadlift-with-posterior-pull" target="_blank" rel="noopener" style="letter-spacing: 0px;">Dumbell deadlifts with </a><a id="posterior" data-tip="1565" target="_blank" href="/glossary-term/posterior" class="glossary">posterior</a> pull</li>
 <li><span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;"><a href="https://brookbushinstitute.com/videos/lateral-lunge-front-rack-resistance" target="_blank" rel="noopener" style="letter-spacing: 0px;">Frontal plane lunge to </a><a id="balance" data-tip="1190" target="_blank" href="/glossary-term/balance" class="glossary">balance</a> (front rack load)</li>
 </ul>
 </li>
 <li><span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Active rest (corrective: activation): 
 <ul>
 <li><a href="https://brookbushinstitute.com/videos/tibialis-anterior-reactive-activation" style="letter-spacing: 0px;">Heel walks</a></li>
 </ul>
 </li>
</ul>

Course Summary: Training Frequency and Recovery Between Sessions

Webinar: Acute Variables Frequency and Recovery

Position Statement and Practical Application

Research Findings: Summary

Research Findings

Research Findings: Blood Chemistry

<h3>Frequency: Older Adults</h3>
<ul>
 <li>Similar Improvements: Elderly exercisers may exhibit a significant improvement in body composition following 3-9 months of resistance training; however, training frequencies of 1-3x/week may result in similar body composition changes (even when exhibiting obesity).
 <ul></ul>
 </li>
 <li><span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Significant Differences: 
 <ul>
 <li><span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">2 - 3x/week: Elderly exercisers exhibited larger improvements in regional fat mass, total fat mass, waist-to-hip ratio, and/or body fat percentage when the frequency was increased from 2x/week to 3x/week during an 8 - 24 week resistance training program. Further, some of these studies demonstrated that significant improvements in body composition only occurred for groups performing resistance training with a frequency of 3x/week.</li>
 <li><span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">1 - 3x/week: Compared to resistance training 1x/week, elderly exercisers performing resistance training 3x/week are likely to exhibit larger changes in strength, body weight, BMI scores, waist circumference, and/or body fat percentage. However, strength and lean mass may increase more with less frequent higher-intensity sessions. Additionally, 1x/week may be insufficient to result in continued improvements in body composition.</li>
 <li><span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Observational Studies: <a id="observational-study" data-tip="1402" target="_blank" href="/glossary-term/observational-study" class="glossary">Observational studies</a> demonstrate that elderly exercisers performing resistance training 2x/week or 3x/week may exhibit similar increases in strength; however, body fat percentage may improve with each increase in frequency, and significant improvements may require a frequency of 3x/week.</li>
 </ul>
 </li>
</ul>
<h3><span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Frequency: Body Composition and Young Adults</h3>
<ul>
 <li>No Change in Body Composition: Resistance training alone (up to 3x/week) is not ideal for improving the body composition of novice adult exercisers.</li>
 <li>Similar Changes in Body Composition: Young adults may exhibit significant improvements in body composition following 8 - 10 weeks of a full-body resistance training program; however, the magnitude of body composition improvements may not be influenced by the frequency (days/week) of resistance training.&#xA0;&#xA0;</li>
 <li>Significant Differences in Body Composition: <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Young adults are likely to exhibit larger improvements in body composition when comparing resistance training 4x or more/week to 3x or less/week. Note, the studies in this section included resistance training programs with significantly larger exercise volumes than those described in previously mentioned studies.&#xA0;</li>
</ul>
<h3><span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Frequency: Body Composition and Volume-equated Routines</h3>
<ul>
 <li>No Change in Body Composition:
 <ul>
 <li>3-6 sets/exercise/week and 12-24 weeks of training: Young and elderly adult exercisers performing 12 -24 weeks of resistance training, with a training volume of 3-6 sets/muscle group/week, regardless of the training frequency (1-3x/week), are unlikely to exhibit significant changes in body mass, body mass index, fat mass, skinfold thickness, or waist and limb circumference.</li>
 <li>9-12 sets/exercise/week and 6-8 weeks of training: Body composition changes may not be significant following 6-8 weeks of resistance training, even with relatively high volumes (9-12 sets/exercise/week) and frequencies (2-6x/week).&#xA0;</li>
 </ul>
 </li>
 <li>Similar Improvements in Body Composition: A relatively high volume of resistance training (10 - 12 sets/muscle group/week for 4 - 20 weeks) may result in significant improvements in body composition; however, when resistance training volume is equated, the frequency may not significantly affect outcomes.</li>
 <li>Significant Differences in Changes in Body Composition: <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">When sets/muscle group are equated during relatively high-volume resistance training, training frequency may have a significant influence on the amount of body composition improvement. It could be hypothesized that 2-3x/muscle group/week (depending on the volume of each session) is the ideal frequency for optimizing total reps/session or total load lifted (reps x load/week), resulting in larger total volumes of exercise, larger increases in <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> mass, and more total calories burned.</li>
</ul>
<span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;"><img alt="Hypertrophy of the abdominial muscles" title="Image of hypertrophy in the abdominal muscles" src="https://www.datocms-assets.com/25800/1669061630-abdominal-hypertrophy.jpg">

Research Findings: Body Composition

<h3>Frequency and Recovery Time: Hypertrophy and Muscle Fiber Changes</h3>
<ul>
 <li>Hypertrophy: <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">The research available introduces confounding variables including the effects of isotonic versus concentric contractions and the frequency of sessions versus the total number of sessions. However, it may be implied that performing a session type (concentric, isotonic, isometric, etc) just 1x/week (or less) is insufficient to result in significant <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> changes (type II <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> hypertrophy and proportion changes); and conversely, more than 2x/week may not result in additional benefits.</li>
 <li>Muscle Fiber Damage: <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Resistance training results in far more type IIa and type IIx than type I <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">Muscle Fiber</a> damage, which may partially explain why resistance training results in much larger changes in type II <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">Muscle Fiber</a> size and proportion. Further, <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">Muscle Fiber</a> damage following the 1st session of a new resistance training routine will likely result in significantly more <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">Muscle Fiber</a> damage than a 2nd session of a similar routine, suggesting significant adaptations to resistance training occurs within days of the 1st session.</li>
</ul>
<h3><span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Frequency and Recovery Time: Hypertrophy and Older Exercisers</h3>
<ul>
 <li>Comparing 1, 2, or 3x/week: <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">O<span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">lder exercisers performing 8 - 24 weeks of resistance training with a frequency of 1, 2, or 3x/week may exhibit similar increases in lean body mass, even when 3x/week results in more total training volume.<span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;"> However, larger changes in body fat percentage may be exhibited when a resistance training frequency of 3x/week is combined with additional exercise (e.g. aerobic activity).&#xA0;</li>
 <li>Frequency and Load: Older exercisers may exhibit larger increases in lean body mass with heavier loads; however, an increase in exercise frequency may not result in additional improvements. Further, the combination of low-intensity (40% of 1-RM) and low-frequency (1x/week) may be insufficient to achieve <a id="optimal" data-tip="1571" target="_blank" href="/glossary-term/optimal" class="glossary">optimal</a> improvements in strength or lean mass.</li>
 <li>Altered Frequency Following an Initial Training Period:&#xA0;
 <ul>
 <li>Altered Frequency: Older exercisers may continue to exhibit increases in lean mass (and strength) when an initial 12-week training period with a frequency of 1-2x/week, is followed by 12 - 24 more weeks with a frequency of 2-3x/week. Additional training of 1x/week may be insufficient to maintain lean <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> mass, despite continued improvements in strength.&#xA0;</li>
 <li>Following a Detraining Period: Older exercisers performing resistance training 2x/week or 3x/week exhibit similar increases in lean mass and strength following an initial 12-week training period, similar amounts of lean tissue maintained while detraining, and similar increases in lean mass and strength when training is resumed 2x/week or 3x/week.&#xA0;</li>
 </ul>
 </li>
</ul>
<h3>Frequency: Hypertrophy, Young Adults, and Volume Equated Studies</h3>
<ul>
 <li>1x/week versus 2x/week: Following 6-8 weeks of resistance training, with the volume of exercise equated, frequencies of 1x/week or 2x/week will likely result in similar improvements in lean <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> mass and strength. However, despite attempts to equate volume, 2x/week is likely to result in larger improvements in loads lifted during training, total weekly load lifted, more exercise volume, larger improvements in RPE relative to load; and potentially, larger improvements in isometric and endurance strength. Conversely, for experienced exercisers only performing 3 sets/muscle group/week, performing them in a single session may result in more hypertrophy.&#xA0; &#xA0;</li>
 <li>1x/week versus 3x/week: Following 8 - 12 weeks of resistance training, with the sets/exercise/week equated, 1x/week and 3x/week are likely to result in similar improvements in hypertrophy; however, 3x/week may result in lower RPE, larger improvements in isometric strength, and potentially larger improvements in 1-RM strength of the exercises performed during the program.</li>
 <li>2x/week versus 3x/week: Similar to the previously mentioned findings of volume-equated studies comparing 1x/week to 2x/week, and 1x/week to 3x/week, 6 - 8 weeks of resistance training with a frequency of 2x/week and 3x/week are likely to result in similar improvements in hypertrophy and strength. However, 3x/week is likely to result in larger total loads lifted during training and a larger volume of exercise/week (reps x load x sets).</li>
 <li>2x/week versus 4x/week: Improvements in strength and hypertrophy are likely to be similar when comparing 6 - 20 weeks, of volume-equated, resistance training with frequencies of 2x/week or 4x/week. However, the differences between groups for some outcome measures may suggest that 2x/week is slightly <a id="superior" data-tip="1570" target="_blank" href="/glossary-term/superior" class="glossary">superior</a> for improving hypertrophy, and 4x/week is slightly <a id="superior" data-tip="1570" target="_blank" href="/glossary-term/superior" class="glossary">superior</a> for improving strength. Note, a frequency of 4x/week implies two training sessions will be performed on consecutive days.&#xA0;</li>
 <li>1-4x/week: Again, studies suggest that improvements in strength and hypertrophy are likely to be similar when comparing 7-10 weeks of volume-equated resistance training with frequencies of 1-4x/week. However, the differences between groups for some outcome measures likely suggest that increasing training frequency may increase hypertrophy, assuming that a split routine is adopted and training for the same <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> group does not occur on consecutive days. Last, when comparing volume-equated resistance training routines with a frequency of 1-2x/week, to 4x/week for the same <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> groups, it is likely that 1-2x/week results in better outcomes than 4x/week.</li>
 <li>Higher Frequencies: Improvements in strength and hypertrophy are likely to be similar when comparing 6-8 weeks of volume-equated resistance training with a frequency of 3-6x/week. However, it is likely that targeting similar <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> groups 2-3x/week will result in larger improvements in strength and hypertrophy than 1x/week, and perhaps 5x/week.</li>
</ul>
<h3>Frequency: Additional Hypertrophy Findings</h3>
<ul>
 <li>Complex Programs: Two studies compared 8 and 24 weeks of resistance training, with a frequency of 3x/week or 4x/week and more complex program designs; however, this complexity introduces several confounding variables. Both studies demonstrated a significant increase in <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> hypertrophy for all training frequencies and programs, which may <a id="base-of-support" data-tip="1197" target="_blank" href="/glossary-term/base-of-support" class="glossary">support</a> the increase in complexity but also suggests additional research is needed to isolate variables and the implicated change in outcomes. Additional implications include larger improvements in hypertrophy resulting from the performance of fewer high-quality sets/routines, <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> groups are not targeted on consecutive days, the inclusion of higher-intensity training (heavier loads and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training), and the periodization of acute variables (load, reps, sets, etc.).&#xA0;</li>
 <li>Menstrual Cycle Adjusted Programs: Based on the study Wikstron-Frisen (2017), larger improvements in lower extremity hypertrophy may result from performing higher volume training (5x/week) during the first 2 weeks of the menstrual cycle than performing higher volume training during the second 2 weeks.</li>
 <li>Adolescent Athletes: A study by DeRenne et al. (1996) may imply that adolescents participating in organized sports following a pre-season resistance training program may exhibit larger increases in hypertrophy with an in-season resistance training frequency of 2x/week, when compared to 1x/week.</li>
 <li>Additional Findings: An 8-week program of leg extensions, regardless of training frequency (2, 3, or 5x/week), may be insufficient to result in lower extremity hypertrophy. Further, increases in hypertrophy may be similar following resistance training programs with a frequency of 2x/week or 3x/week, but significantly less for 1x/week.&#xA0;</li>
</ul>

Research Findings: Hypertrophy

Research Findings: Strength, Power, and Delayed Onset Muscle Soreness (DOMS)

<h3>Frequency and Recovery Time: EMG Activity</h3>
<ul>
 <li>Frequency:&#xA0;<span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;"> Average and peak EMG activity may be reduced for several days following an initial resistance training session, with peak decreases potentially occurring 2 days post-exercise, and requiring up to 7 days to return to pre-exercise values. However, this decrease may only occur during initial sessions. Additionally, the number of days of rest between sessions is likely to have a significant effect on exercise volume (reps x sets x load), but may not have a significant effect on peak or average EMG activity. Last, improvements in maximal EMG activity may be correlated with an increase in 1-RM strength and require an extended training period of 1-2 sessions/week.</li>
 <li>Age: Post-exercise reductions in average and peak EMG activity may not be strongly correlated with force production or soreness, and peak reductions in EMG activity may occur hours or 1-2 days post-exercise. Novice exercisers are likely to exhibit larger reductions in EMG activity than experienced exercisers, young and middle-aged adults are likely to exhibit similar reductions, and older individuals may exhibit larger reductions than young and middle-aged individuals.</li>
 <li>Contraction Type, Tempo, and Forced Reps: Larger post-exercise reductions in peak EMG activity (and TMS) may be exhibited following eccentric contractions (when compared to concentric or isometric contractions), and/or slower rep tempos (longer time under <a id="tension" data-tip="1229" target="_blank" href="/glossary-term/tension" class="glossary">tension</a>). Conversely, an increase in load may not have a significant effect on post-exercise EMG activity.</li>
</ul>
<h3>Frequency: Bone Mineral Density, Resting Blood Pressure, Functional Testing, and Psychosocial Improvements</h3>
<ul>
 <li>Bone Mineral Density: Resistance training with a frequency of at least 3x/week, and loads of 8-RM/set or 80% of 1-RM, may be necessary to improve bone mineral density; however, it is also likely that older individuals will not exhibit significant improvements regardless of training frequency or load. Note, the site of bone mineral density <a id="assessment" data-tip="1478" target="_blank" href="/glossary-term/assessment" class="glossary">assessment</a> may affect research findings (e.g. the trochanter score may be a more <a id="sensitivity" data-tip="1227" target="_blank" href="/glossary-term/sensitivity" class="glossary">sensitive</a> measure than tibial volumetric cortical density).&#xA0;&#xA0;</li>
 <li>Resting Blood Pressure: Resistance training may have no effect on resting blood pressure or result in relatively small improvements (average 2 - 4 mmHg), regardless of the training frequency (1 - 3x/week).</li>
 <li>Functional Improvements:
 <ul>
 <li>1x/week or 2x/week: <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Older exercisers performing 10 weeks to 1 year of resistance training 1x/week may exhibit improvements in flexibility, the 6-min walk <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>, and grip strength; however, 2x/week is likely to result in significantly larger improvements, including additional improvements in leg <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, the 8-foot up-and-go <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>, and the chair stand <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>.&#xA0;</li>
 <li>2x/week or 3x/week: Older exercisers performing 8 - 30 weeks of resistance training 2x/week or 3x/week are likely to exhibit similar improvements on a variety of functional outcome measures (including sit and reach, back scratch, <a id="balance" data-tip="1190" target="_blank" href="/glossary-term/balance" class="glossary">balance</a> with normal and perturbed stance with eyes open or closed, sit-to-stand <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>, time to stand up from the floor, 8-foot up-and-go <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>, 10-meter walk <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>, 6-min walk <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>, 30-second chair stands, 30-second arm curl, <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> fatiguability, handgrip dynamometer isometric strength, and medicine ball throw distance).</li>
 <li>1x/week, 2x/week, or 3x/week: R<span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">esistance training for 16 - 24 weeks significantly affects functional outcomes; however, the training frequency may not. The studies that do imply frequency has a significant effect on functional outcomes suggest that 3x/week may result in additional benefits not attained by training 1x/week or 2x/week.</li>
 </ul>
 </li>
 <li>Psychosocial Improvements: Resistance training for 12 weeks to 1 year has a significant effect on many quality of life, psychosocial, and psychomotor outcome measures; however, the frequency of training may be less influential. The study by Kekalainen et al. may suggest that 2x/week or more may result in additional improvements; however, it may be necessary to consider the participant&apos;s confidence in adhering to an increase in training frequency.</li>
</ul>
<h3>Frequency: Rehabilitation and Core Muscle Exercise</h3>
<ul>
 <li>Lumbar Extension Programs: <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Low back strength, pain, and disability improve more following lumbar extension exercise frequency of 1x/week when compared to 0.5x/week (1 time every other week). Although a frequency of 1 - 3x/week during an initial training period (e.g. initial 12 weeks) may result in similar improvements for some outcome measures, it is likely that 2 - 3x/week is <a id="superior" data-tip="1570" target="_blank" href="/glossary-term/superior" class="glossary">superior</a> to 0.5 - 1x/week for improving dynamic strength, pain, and function. Further, at least 1x/week is required to maintain benefits beyond the initial training period, and 2 - 3x/week is likely necessary to continue improving.&#xA0;</li>
 <li>Neck, Shoulders, and Core: <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Shoulder exercises performed 1x/day or 2x/day may have similar effects on neck and shoulder pain. <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">However, performing neck and trunk exercises 2 - 3x/week will likely result in significantly larger strength improvements than 1x/week.&#xA0;&#xA0;</li>
</ul>
<h3>Recovery Time: Individual Differences</h3>
<ul>
 <li>Individual Differences: <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Different individuals, both novice and experienced, can exhibit dramatically different post-exercise recovery times for strength, soreness, arm circumference, ROM, and serum concentrations of markers of <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> damage and inflammation. Individuals may also exhibit different amounts of adaptation and improvement in recovery times between the 1st and 2nd sessions of the same routine. Further, an exerciser&apos;s perception of recovery may lag behind objective measures of recovered strength on subsequent days.</li>
</ul>
<h3>Pivotal Studies: Work, EMG activity, Lactate Concentrations, and Days Rest</h3>
<ul>
 <li><span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Work, EMG activity, Lactate Concentrations, and Days Rest: These studies were considered pivotal due to their <a id="relevance" data-tip="1504" target="_blank" href="/glossary-term/relevance" class="glossary">relevance</a> in making <a id="evidence-based-practice" data-tip="1538" target="_blank" href="/glossary-term/evidence-based-practice" class="glossary">evidence-based</a> recommendations on days rest between sessions and session frequency. Based on these studies, the number of days of rest between sessions has no influence on EMG activity, 1 day of rest before a 2nd session is likely to result in a significant decrease in the volume of work and higher blood serum concentrations of lactate immediately post-exercise, 2 days of rest is likely to result in similar lactate concentrations and similar work, and 3 of days rest may result in an increase in work performed.</li>
</ul>

Research Findings: Additional Topics

Blood Serum Concentrations

Summary
<ul>
 <li>Frequency of 2-4 Days Per Week: Increased frequency is likely beneficial for improving body composition, hypertrophy, strength, and power; however, the relationship between frequency and post-exercise serum concentrations of inflammatory and anabolic markers is less clear. An increase in resistance training frequency may decrease cortisol, increase insulin-like growth factor 1 (IGF-1), increase testosterone, and improve the testosterone-to-cortisol ratio; however, it is also likely that frequency is less influential than other acute variables (e.g. load, volume, etc.).</li>
 <li>Following a period of Reduced Frequency: A reduction in training frequency to 1x/week, following an initial 12-week training period of higher frequency, may not be sufficient to maintain or improve changes in CSA or body composition; however, strength may continue to increase. Further, reduced training frequency resulted in an increase in resting testosterone for in-season male athletes, but no change in testosterone concentrations for older female novice exercisers. These findings may affirm little to no correlation between exercise-induced changes in testosterone concentrations and health and performance improvements.</li>
 <li>Following a Detraining Period: Frequency may not have a significant influence on resting IGF-1, testosterone, AOPP, or TRAP; however, exercising 2-3/week may increase TRAP, and detraining may result in a decrease in resting testosterone. Again, the measured blood markers did not correlate with changes in strength or hypertrophy.</li>
</ul>
<h3>Frequency of 2-4 Days Per Week</h3>
The research does not demonstrate a strong correlation between exercise frequency and post-exercise changes in blood serum concentrations of various inflammatory and anabolic markers, and almost no correlation between these changes and improvements in performance. An RCT by Marx et al. compared 34 female (aged: 22.6 &#xB1; 3.7 years) novice exercises who were randomly assigned to a control group (no exercise), a 3x/week group, or a 4x/week group. Participants who exercised 3x/week completed circuit-style training (leg press, bench press, leg curls, rows, standing calf raises, bicep curls, sit-ups, pullovers, military press, hip abduction/adduction, knee extensions, chest flyes, leg curls, <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> raises, seated calf raises, tricep pushdowns, back extensions, upright rows, rotator cuff exercises, and lat pulldowns) with 1 set/exercise, 8-12 reps to failure/set, a moderate (1-2 min) rest between exercises, and a slow (4:0:2) repetition tempo. Participants who exercised 4x/week completed a 2-day split routine (Day 1: hang cleans, squats, bench press, push press, leg curls, sit-ups, rotator cuff exercises; Day 2: upright rows, dumbbell military press, bicep curls, tricep pushdowns, lat pulldowns, seated rows, sit-ups, side bends, <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> hip flexions, leg curls, calf raises and lunges) with 2-4 set/exercise, 3-15 reps/set (undulating periodization), and moderate to long rest between sets (1-4 min). The finding demonstrated that neither group exhibited changes in serum concentrations of human growth <a id="hormone" data-tip="1266" target="_blank" href="/glossary-term/hormone" class="glossary">hormone</a> (HGH). The 4x/week group exhibited significantly larger changes in serum concentrations including decreased cortisol, increased IGF-1, increased testosterone, and increased testosterone-to-cortisol ratio. Additionally, the 4x/week group exhibited larger improvements in body composition, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, max strength, and strength endurance (1). Stec et al. compared 64 older male and female (aged: 65.5 &#xB1; 3.6 years) novice exercisers who were randomly assigned to groups performing 2x/week with isotonic repetitions, 3x/week with isotonic repetitions, 2x/week with a combination of isotonic and concentric only repetitions (1x/week of isotonic, 1x/week of concentric only), or 3x/week with a combination of isotonic and concentric only repetitions (2x/week of isotonic, 1x/week of concentric only). Participants completed a full body program (squats, knee extensions, leg press, heel raises, seated overhead press, chest press, seated cable rows, pulldowns, bicep curls, tricep pushdowns, and abdominal flexions) for 30 weeks, 1-2 sets/exercise, and 10-15 reps near failure/set. None of the groups exhibited a significant change in interleukin-6, tenascin-C, or RPS6 (inflammatory markers). All groups exhibited similar reductions in eIF2be and total p70S6K protein content (anabolic signaling), and NFkB p65n (an inflammatory marker). Only the 3x/week of isotonic exercise group increased the number of TNF receptor 1 and TWEAK receptors (inflammatory markers), and decreased phospho-p70S6K (anabolic signaling). The findings demonstrated that both 3x/week groups, and the 2x/week of isotonic exercise groups, exhibited a significant improvement in body composition, the 3x/week combination group exhibited the largest improvement, and the 2x/week combination group did not exhibit significant improvement. All groups exhibited similar increases in strength and power; however, the 2x/week of combination group achieved at 24 weeks what other groups achieved in 8 weeks. The findings demonstrated that both 3x/week groups, and the 2x/week of isotonic exercise groups exhibited similar increases in <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> CSA; however, the 2x/week combination group did not exhibit a significant increase in <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> size or shift in fiber type ratio. These findings suggest that an increase in inflammatory receptors may be correlated with increased exercise frequency; however, considering that anabolic signaling and inflammatory marker serum concentrations were similar for all groups, there may be little correlation with strength or hypertrophy (2). These studies suggest that increased frequency is likely beneficial for improving body composition, hypertrophy, strength, and power; however, the relationship between frequency and post-exercise serum concentrations of inflammatory and anabolic markers is less clear. An increase in resistance training frequency may decrease cortisol, increase IGF-1, increase testosterone, and improve testosterone-to-cortisol ratio; however, it is also likely that frequency is less influential than other acute variables (e.g. load, volume, etc.).
<h3>Following a Period of Reduced Frequency</h3>
Two studies compared changes in testosterone concentrations, strength, and hypertrophy following an initial 12-week training program, followed by a period of reduced frequency. DeRenne et al. compared 21 male baseball athletes (13.25 &#xB1; 1.26 years old) who were novice exercisers following a pre-season protocol of 3x/week, and then randomly assignment to an in-season protocol of 1x/week or 2x/week. All participants completed a full-body resistance training program (bench press, wide-grip cable pulldowns, leg extensions, leg curls, bicep curls, tricep extensions, rotator cuff exercises, wrist curls, and wrist extensions). The pre-season program was performed for 12 weeks, 3x/week, 3 sets/exercise, 10 reps/set, with 50-100% of 10-RM loads, and the in-season program was performed for 12 weeks, 1x/week or 2x/week, 3 sets/exercise, 10 reps/sets, and 50-75% of 10-RM loads. The findings demonstrated that neither group exhibited significant changes in chest, bicep, waist, or thigh girth; however, the 2x/week group, exhibited a significant increase in lean body mass, and improvement in body composition. Only the 1x/week group exhibited an increase in bench press 10-RM strength during the season, and neither group exhibited a change in leg press 10-RM strength or pull-ups to failure following pre-season training. Interestingly, only the 1x/week group exhibited increased resting testosterone levels compared to pre-season values (3). An RCT by Walker et al. compared 38 older female novice exercisers (aged: 64-75 years) following an introductory resistance training program for 12 weeks, 2x/week, and then random assignment to 24 weeks of a control group (no exercise), 1x/week group, or 2x/week group. The resistance training routine included a full body program (leg press, knee extensions, leg curls, chest press, lat pulldowns, shoulder press, seated rows, bicep curls, tricep pushdowns, abdominal curls, and back extensions). The 12-week introductory period included 2x week, of at least 1 set/exercise, 14-20 reps to failure/set, 50-60% of 1-RM loads, short (1 min) rest between sets, and a moderate (2:0:2) rep tempo. The 24-week intervention period included 1x/week or 2x/week, of 2-5 sets/exercise, 4-12 reps/set, 30-90% of 1-RM loads, and a moderate (1-3 min) rest between sets. Results demonstrated similar increases in cross-sectional area (CSA) of the vastus lateralis and vastus intermedius during the initial training period, followed by maintenance of CSA by the 2x/week group, and a slight decrease in CSA by the 1x/week group. Leg press 1-RM strength (and EMG activity during testing) increased during the introductory period and continued to increase similarly during the experimental period for both groups. Both groups exhibited similar increases in resting testosterone levels (4). These studies imply that a reduction in training frequency to 1x/week, following an initial 12-week training period of higher frequency, may not be sufficient to maintain or improve changes in CSA or body composition; however, strength may continue to increase. Further, reduced training frequency resulted in an increase in resting testosterone for in-season male athletes, but no change in testosterone concentrations for older female novice exercisers. These findings may affirm little to no correlation between exercise-induced changes in testosterone concentrations and health and performance improvements.
<h3>Following a Detraining Period</h3>
Additional studies compare concentrations of post-exercise serum concentration following various training frequencies and a detraining period. Nascimento et al. compared 45 novice female exercisers (aged: &#x2265; 60 years) randomly assigned to a 2x/week group or a 3x/week group. Participants completed a full body program (chest press, leg press, rows, knee extensions, preacher curls, leg curls, tricep pushdowns, and seated calf raises) for 12 weeks, 1 set/exercise, 10-15 reps to failure/set, a moderate rest between exercises (2-3 min), and a rep tempo ratio of 2:1 (eccentric to concentric). Note, this study assessed outcomes following 12 weeks of exercise and then again following 12 weeks of no exercise. Both groups exhibited similar increases in <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> mass following the 12-week intervention and similar maintenance of improvements following 12 weeks of detraining. Neither group exhibited significant changes in resting serum concentration of IGF-1 or testosterone. Interestingly, both groups experienced a reduction in resting testosterone after 12 weeks of no exercise (5). <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Padilha et al. compared 27 novice female exercisers (aged: 68.8 &#xB1; 4.8 years) randomly assigned to a 2x/week or 3x/week program (potentially part of the same experiment above). Participants completed a full body program (chest press, leg press, rows, knee extensions, preacher curls, leg curls, tricep press downs, and seated calf raises) for 12 weeks, 1 set/exercise, 10-15 reps to failure/exercise, moderate rest between exercises (2-3 min), and a rep tempo ratio of 2:1 (eccentric to concentric). Note, participants completed 12 weeks of exercise and then 12 weeks of no exercise. The findings demonstrated that the 3x/week group exhibited larger increases in strength following the training period, but both groups exhibited similar decreases in strength following 12 weeks of detraining. Findings demonstrated that neither group exhibited changes in advanced oxidized protein products (AOPP), both groups exhibited similar increases in total radical-trapping antioxidant parameter (TRAP), and following 12 weeks of detraining TRAP remained elevated (6). These studies suggest that frequency may not have a significant influence on resting IGF-1, testosterone, AOPP, or TRAP; however, exercising 2-3x/week may increase TRAP, and detraining may result in a decrease in resting testosterone. Again, the measured blood markers did not correlate with changes in strength or hypertrophy.

Frequency: Blood Chemistry

Recovery Time: Anabolic Hormones and Markers of Protein Synthesis

Recovery Time: Markers of Muscle Damage and Age

Summary
<ul>
 <li>Reps-to-Failure/Set versus Reps in Reserve/Set: When compared to reps-in-reserve/set, reps-to-failure/set (and increased load) may result in significantly higher post-exercise serum concentrations of creatine kinase, including higher initial increases, higher peak concentrations, and more days exhibiting elevated concentrations. However, significantly higher concentrations are likely a short-term phenomenon, as longer-term training (e.g. 10-week program) results in a significant decrease in post-exercise concentrations.</li>
 <li>Last Set to Failure:&#xA0;When compared to reps-to-failure for all sets, reps-to-failure for only the last set is likely to result in smaller increases in post-exercise serum concentrations of creatine kinase, and potentially a faster return to near pre-exercise concentrations (72 hours compared to 48 hours). However, reps-to-failure for only the last set may still result in significantly higher concentrations than reps-in-reserve for all sets.</li>
</ul>
<h3>Reps to Failure/Set versus Reps in Reserve/Set</h3>
Studies investigating post-exercise serum concentrations of creatine kinase have compared performing reps-in-reserve/set and reps-to-failure/set. As mentioned above, Gonz&#xE1;lez-Badillo et al. compared 9 experienced male exercisers (aged: 23.3 &#xB1; 3.9 years) 5 min, 6 hours, 24 hours, and 48 hours after a reps-to-failure/set protocol and a half-reps/set protocol, performed in random order with 14 days rest between sessions. Participants completed bench press and squats, 3 sets/exercise, with 4 or 8 reps/set, 8-RM loads, with long (10 min) rest between exercises. The findings demonstrated that the reps-to-failure/set protocol resulted in larger decreases in mean bench press and squat bar velocity, and counter-movement vertical jump height. The reps-to-failure/set group only exhibited a trend toward larger increases in serum concentrations of creatine kinase 5 minutes and 48 hours post-exercise (11). Mor&#xE1;n-Navarro et al. compared 10 experienced male exercisers (aged: 21.5 &#xB1; 4.0 years) immediately, 6 hours, 24 hours, 48 hours, and 72 hours post-exercise. Participants completed 3 different exercise protocols separated by 4 weeks in randomized order: the low-volume protocol included 3 sets/exercise, 5 reps/set, without reaching failure (low-volume); the high-volume protocol included 6 sets/exercise, 5 reps/set, without reaching failure (high-volume); and the low-volume to failure protocol included 3 sets/exercise, 10 reps/set, reps to failure/set (low-volume to failure). The exercise protocols included Smith machine bench press and squats, 75% of 1-RM loads, with long (5 min) rest between sets. The low-volume-to-failure protocol was the only protocol to exhibit a decrease in the bench press and squat average propulsive velocity 6 hours post-exercise and exhibit a reduction in countermovement jump height 72 hours post-exercise (compared to 6 hours for other groups). The low-volume-to-failure protocol resulted in elevated creatine kinase concentrations for 72 hours, compared to the 48 hours exhibited by other groups (12). <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Pareja-Blanco et al. compared 10 novice male exercisers (age: 20.6 &#xB1; 2.7 years) immediately, 6 hours, 24 hours, and 48 hours post-exercise after completing 3 different protocols separated by 2 weeks. Protocol 1 (reps to failure protocol) included reps to failure/set with a 10-RM load; protocol 2 (half reps protocol) included 5 reps/set with a 10-RM load; protocol 3 (half reps after training protocol) included 5 reps/set with a 10-RM load after completing a 10-week resistance training program. All protocols included bench presses and squats, 3 sets/exercise, long (5 min) rest between sets, and long (10 min) rest between exercises. The 10-week resistance training program included the same protocol for 10 weeks (18 sessions). The findings demonstrated that the bar velocity for bench press and squats decreased most and the recovery period was longest for the reps to failure protocol, followed by the half reps protocol, and the smallest decrease was exhibited by the half reps following training protocol. Serum concentrations of creatine kinase immediately post-exercise were highest following the reps to failure/set protocol; however, 48 hours post-exercise creatine kinase concentrations were highest for the half reps/set before training protocol. The half-reps/set after training protocol resulted in post-exercise (immediate and 48 hours) concentrations of creatine kinase that failed to reach statistically significant elevations (10). In summary, when compared to reps-in-reserve/set, reps-to-failure/set (and increased load) may result in significantly higher post-exercise serum concentrations of creatine kinase, including higher initial increases, higher peak concentrations, and more days exhibiting elevated concentrations. However, significantly higher concentrations are likely a short-term phenomenon, as longer-term training (e.g. 10-week program) results in a significant decrease in post-exercise concentrations.
<h3>Last Set to Failure</h3>
Two studies were located comparing protocols with a mix of reps-in-reserve/set and reps-to-failure/set. Davies et al. compared 19 experienced exercisers (11 males age: 23 &#xB1; 3 years, 9 females age: 24 &#xB1; 4 years) 4 hours, 24 hours, 48 hours, and 72 hours post-exercise. Participants completed squats, 5 sets/exercise, 5 reps/set, 80% 1-RM load, moderate (1.5 min) rest between sets, with a slow (6-sec/rep) rep tempo. Participants then performed squats for a 6th set, 80% 1-RM, with reps to failure. All values were compared to pre-exercise values. The findings demonstrated that women exhibited a larger increase in DOMS, a larger decrease in strength, and men exhibited a larger decrease in <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>. Males and females exhibited similar increases in creatine kinase 24 hours post-exercise; and unfortunately, no other time periods were reported as part of this study (26). Mangine et al. compared 14 experienced male exercisers (aged: 24.6 &#xB1; 3.0 years), 6 hours, 24 hours, 48 hours, and 72 hours post-exercise. All participants completed the bench press exercise, 5 sets/session, 80% of 1-RM loads, long (3-4 min) rest between sets, with 2 different rep/set protocols on different days in randomized order. The &quot;last set only&quot; protocol included 4 sets/session with a self-determined 3 reps in reserve/set, and a 5th set with reps to failure/set, and the &quot;all sets&quot; protocol included all 5 sets/session performed with reps to failure/set. The findings<span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;"> demonstrated that the all-sets group exhibited a significantly larger decrease in reps/set and average bar velocity 24 and 48 hours post-exercise, and both groups exhibited similar reps and velocity as the initial set 72 hours post-exercise. Both groups exhibited increases in serum concentrations of creatine kinase post-exercise; however, the all-sets group exhibited larger increases 24 hours, 48 hours, and 72 hours post-exercise. Note, 72 hours post-exercise, the all-sets protocol still exhibited elevated concentrations, and the last-set-only protocol exhibited near pre-exercise concentrations (27)<span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">. <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">These studies imply that when compared to reps-to-failure for all sets, reps-to-failure for only the last set is likely to result in smaller increases in post-exercise serum concentrations of creatine kinase, and potentially a faster return to near pre-exercise concentrations (72 hours compared to 48 hours). However, reps-to-failure for only the last set may still result in significantly higher concentrations than reps-in-reserve for all sets.
<span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;"><img alt="An athlete preparing to deadlift" title="Image of strength athlete performing deadlifts" src="https://www.datocms-assets.com/25800/1679876688-adobestock_65275423.jpeg">

Recovery Time: Markers of Muscle Damage and Reps to Failure

Recovery Time: Markers of Muscle Damage and Acute Variables

<h3>Summary</h3>
<ul>
 <li>Following a Second Session: Following the first session of a resistance training routine, increases in post-exercise serum concentrations of <a id="myoglobin" data-tip="1262" target="_blank" href="/glossary-term/myoglobin" class="glossary">myoglobin</a> and creatine kinase are likely to be significant, peaking 4 - 5 days post-exercise, and concentrations may remain elevated for 7 days or longer. However, following repeated sessions of the same routine, the post-exercise elevations are likely to decrease dramatically, perhaps failing to reach statistical significance, despite significant <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> damage exhibited on micrographs. Note, a threshold level of <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> damage may be necessary to result in statistically significant changes in serum concentrations, and elevated creatine kinase levels may be correlated with some, but not all mechanical outcome measures (strength, ROM, etc.).&#xA0;</li>
 <li><span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Multiple Sessions: Post-exercise serum concentrations of markers of <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> damage (e.g. creatine kinase, <a id="myoglobin" data-tip="1262" target="_blank" href="/glossary-term/myoglobin" class="glossary">myoglobin</a>, and lactate dehydrogenase) are likely to increase dramatically following a single resistance training session, and concentrations may remain elevated for a week or more.&#xA0; However, following 2 or 3 similar resistance training sessions, it is likely that concentrations will fail to reach statistically significant elevations at anytime point post-exercise.&#xA0;<span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;"></li>
 <li><span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Comparing Age Groups: Following a single session of resistance training, older exercisers will likely exhibit larger and longer changes in strength, ROM, swelling, DOMS, and higher creatine kinase concentrations. However, older exercisers may be as likely as younger exercisers to adapt to resistance training, as repeated sessions results in similar improvements in post-exercise outcome measures for all age groups.&#xA0;</li>
 <li>Strange Finding: Adaptations Across Limbs: <a id="unilateral" data-tip="1551" target="_blank" href="/glossary-term/unilateral" class="glossary">Unilateral</a> resistance training results in some adaptation of both limbs including a significant reduction in the elevation of creatine kinase concentrations following training of the other limb.</li>
</ul>
<h3>Following a Second Session</h3>
Research has investigated the difference between post-exercise serum concentrations of <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> damage following the 1st and 2nd sessions of the same routine. Chen et al. compared 15 novice male exercisers (age: 20-25 years) 1 day, 2 days, 3 days, 4 days, and 5 days post-exercise. Participants completed full body eccentric exercises performed in random order (elbow flexion, elbow extension, chest press, knee extensions, knee flexion, plantar flexion, lat pulldowns, abdominal crunches, and back extensions) for 5 sets/exercise, 10 reps/set, 80% MVC load, short (15 sec) rest between reps, moderate (2 min) rest between sets, and a slow (5 sec) rep tempo. Participants then rested for 2 weeks and repeated the program. The findings demonstrated that following the first session MVIC and DOMS exhibited significant change post-exercise, and a return to pre-exercise values started on the 5th day. Following the second session, changes in MVIC and DOMS were significantly less, and pre-exercise values were attained by the 2nd or 3rd day. Serum concentrations of creatine kinase and <a id="myoglobin" data-tip="1262" target="_blank" href="/glossary-term/myoglobin" class="glossary">myoglobin</a> increased significantly following the 1st session, <a id="myoglobin" data-tip="1262" target="_blank" href="/glossary-term/myoglobin" class="glossary">myoglobin</a> reached peak values on day 3, and creatine kinase reached peak values on day 4, with values for both exhibiting some improvement but not reaching pre-exercise values by day 5. Following the second session, creatine kinase and <a id="myoglobin" data-tip="1262" target="_blank" href="/glossary-term/myoglobin" class="glossary">myoglobin</a> concentrations failed to reach statistically significant changes (35). Coratella et al. compared 13 active males (age: 21.7 &#xB1; 3.1 years) immediately post-exercise, 1 day, 2 days, 3 days, and 4 days post-exercise. Participants completed squats on a flywheel ergometer, 10 sets/exercise, 10 reps/set, and short (1 min) rest between sets. Note that participants completed two exercise sessions separated by 2 weeks. Results demonstrated that following the first session, MVIC decreased significantly, with the largest decrease exhibited immediately post-exercise, and a return to near pre-exercise values on day 4. Following the 2nd session, MVIC decreased less and returned to pre-exercise values 2 days post-exercise. DOMS increased significantly following the first session, peaked 1 - 2 days post-exercise, and improved but did not return to pre-exercise values on days 3 and 4. Following the second session DOMS increased less, peaked on day 2, and was near pre-exercise values on day 3. Last, following the first session, post-exercise serum concentrations of creatine kinase increased significantly, peaked 1-2 days post-exercise, and improved but did not return to pre-exercise values by day 4. Following the 2nd session, post-exercise serum concentrations of creatine kinase did not significantly increase (36). Hortob&#xE1;gyi et al. compared 9 male and 9 female novice exercisers (age: 22.6 &#xB1; 2.7 years) 2 days, 4 days, and 7 days post-exercise. Participants were randomly assigned to an exercise or control (no exercise) group, and the exercise group completed 2 sessions separated by 2 weeks. The exercise protocol included eccentric knee extensions, 10 sets/exercise, 10 reps/set, 80% of maximum loads, and long (3 min) rest between sets. The findings demonstrated that following the first session, exercisers exhibited significant decreases in dynamic, isokinetric, and isometric strength, as well as increases in DOMS, with some values failing to return to pre-exercise values 7 days post-exercise. Following the second session changes in strength and DOMS failed to reach statistical significance. Compared to pre-exercise values, following the first session exercisers exhibited significant increases in serum concentrations of creatine kinase, with peak values exhibited 2 days post-exercise, near peak values exhibited 4 days post-exercise, and a return to near pre-exercise values 7 days post-exercise. Following the second session increases in serum concentrations of creatine kinase did not increase significantly. Interestingly, this study also assessed 3 participants with electron micrographs of the vastus lateralis. Following the 1st session, significant <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> damage (&quot;disorganization&quot; of myofilaments, sarcomeres, and Z-lines) was present 2 days post-exercise and returned to near normal 7 days post-exercise. Following the 2nd session a similar trend was noted; however, the magnitude of damage was less; 65 &#xB1; 12% of pixels compared to 23 &#xB1; 4% of pixels 2 days post-exercise (37). These studies suggest that following the first session of a resistance training routine, increases in post-exercise serum concentrations of <a id="myoglobin" data-tip="1262" target="_blank" href="/glossary-term/myoglobin" class="glossary">myoglobin</a> and creatine kinase are likely to be significant, peaking 4 - 5 days post-exercise, and concentrations may remain elevated for 7 days or longer. However, following repeated sessions of the same routine, the post-exercise elevations are likely to decrease dramatically, perhaps failing to reach statistical significance, despite significant <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> damage exhibited on micrographs. Note, a threshold level of <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> damage may be necessary to result in statistically significant changes in serum concentrations, and elevated creatine kinase levels may be correlated with some, but not all mechanical outcome measures (strength, ROM, etc.).&#xA0;
<h3>Multiple Sessions</h3>
Two studies were located comparing serum concentrations of creatine kinase following multiple sessions. Chen et al. compared 15 novice male exercisers (age: 21.8 &#xB1; 1.9 years) immediately, 3 hours, 1 day, 2 days, 3 days, 4 days, and 5 days post-exercise. The exercise protocol was repeated 4 times, with 4 weeks between sessions, during a 16-week period. Participants completed eccentric elbow flexion via an isokinetic dynamometer, 4 sets/exercise, 30 reps/set, short (10 sec) rest between reps, and a fast (1-sec) rep tempo. The findings demonstrated significant changes and long recovery periods for strength (MVIC and MVCC) and DOMS following the first session and a reduction in the magnitude of change and recovery duration with each subsequent session. However, serum concentrations of creatine kinase, lactate dehydrogenase, and <a id="myoglobin" data-tip="1262" target="_blank" href="/glossary-term/myoglobin" class="glossary">myoglobin</a> may have exhibited the most dramatic changes from session to session. Although, significant increases were exhibited immediately following session 1 that continued to increase during each day of the reassessment period (highest values exhibited on day 6); following sessions 2-4, increases in serum concentrations failed to reach statistical significance (38). As mentioned<span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">&#xA0;above, Pareja-Blanco et al. compared 10 novice male exercisers (age: 20.6 &#xB1; 2.7 years) immediately, 6 hours, 24 hours, and 48 hours post-exercise after completing 3 different protocols separated by 2 weeks (and following a resistance training program). Protocol 1 (reps to failure protocol) included reps to failure/set with a 10-RM load; protocol 2 (half reps protocol) included 5 reps/set with a 10-RM load; protocol 3 (half reps after training protocol) included 5 reps/set with a 10-RM load after completing a 10-week resistance training program. All protocols included bench press and squats, 3 sets/exercise, long (5 min) rest between sets, and long (10 min) rest between exercises. The 10-week resistance training program included the same protocol for 10 weeks (18 sessions). The findings demonstrated that the bar velocity for bench press and squats decreased most and the recovery period was longest for the reps-to-failure/set protocol, followed by the half reps protocol, and the smallest decrease was exhibited by the half reps following training protocol. Serum concentrations of creatine kinase immediately post-exercise were highest following the reps to failure/set protocol, but 48 hours post-exercise creatine kinase concentrations were highest for the half reps/set before training protocol. Again, the most dramatic change may be the half-reps/set after the training protocol exhibiting no significant increase in creatine kinase immediately post-exercise or 48 hours post-exercise (10). In summary, p<span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">ost-exercise serum concentrations of markers of <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> damage (e.g. creatine kinase, <a id="myoglobin" data-tip="1262" target="_blank" href="/glossary-term/myoglobin" class="glossary">myoglobin</a>, and lactate dehydrogenase) are likely to increase dramatically following a single resistance training session, and concentrations may remain elevated for a week or more. However, following 2 or 3 similar resistance training sessions, it is likely that concentrations will fail to reach statistically significant elevations at any time post-exercise.
<h3>Comparing Age Groups</h3>
Two studies compared the effects of repeated sessions on markers of <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> damage with participants of various age groups. As mentioned above, <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Chen et al. compared 39 novice male exercisers (pre-adolescents age: 9.4 &#xB1; 0.5 years, adolescents age: 14.3 &#xB1; 0.4 years, adults age: 22.6 &#xB1; 2.0 years) immediately and 1-5 days post-exercise. Participants completed eccentric elbow flexion via an isokinetic dynamometer, 5 sets/exercise, 6 reps/set, a short (10-sec) rest between reps, moderate (2 min) rest between sets, and a moderate (x:1:90&#xB0;/sec) rep tempo. Note, participants completed two exercise bouts separated by 3 weeks. The findings demonstrated that adult exercisers exhibited larger changes than younger exercisers in strength, ROM, circumference, and swelling after the 1st and 2nd bouts of exercise; however, significant improvements were exhibited during recovery from the 2nd bout. <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Serum concentrations of creatine kinase and <a id="myoglobin" data-tip="1262" target="_blank" href="/glossary-term/myoglobin" class="glossary">myoglobin</a> were assessed 3 days and 5 days post-exercise. Following the 1st session concentrations were highest for adult exercisers, followed by adolescent exercisers, and the lowest for pre-adolescents, and values continued to increase throughout the testing period. Following the 2nd session, concentrations of creatine kinase were similar to pre-exercise concentrations during the 3rd and 5th days for all groups (17). Also mentioned above, Clarkson et al. compared 20 experienced and novice, young adult and older female exercises (10 young, age: 23.6 &#xB1; years, 10 older, age: 67.4 &#xB1; 5.3 years) immediately, 1 day, 2 days, 3 days, 4 days, and 5 days post-exercise. Participants completed eccentric bicep curls, 2 sessions, 1 set/session, 24 reps/set, 115% MVIC, short (12 sec) rest between reps, a moderate (3 sec) rep tempo, and 7 days rest between sessions. The findings demonstrated that DOMS increased significantly post-exercise following both sessions. Following session 1, young exercisers exhibited peak soreness 1-day post-exercise, with a gradual decrease in soreness to near pre-exercise values on days 4 and 5. Following the 2nd session, exhibited significantly less soreness, respectively peaking 1 day post-exercise, and returning to near pre-exercise-values-on days 2 and 3. Elderly exercisers exhibited significantly more soreness following session 1, exhibiting peak values 2 days post-exercise, but returning to near pre-exercise values on days 4 and 5. Following the 2nd session, elderly exercisers exhibited the smallest increases in DOMS, peaking 1 day post-exercise, but maintaining values that were near pre-exercise values throughout the reassessment period. The findings demonstrated that serum concentrations of creatine kinase increased significantly following the 1st session. Young exercisers exhibited a significant increase in concentrations 1 day post-exercise and exhibited a continuous increase in serum concentrations throughout the 5 day reassessment period. Following the 2nd session, young exercisers exhibited peak creatine kinase concentrations 1 day post-exercise and returned to pre-exercise values by the 4th day of re-assessment. Following the 1st session, elderly exercisers exhibited a significant increase in creatine kinase values that continued to increase throughout the 5 day reassessment period. Prior to the 2nd session, serum concentrations of creatine kinase were elevated, and continued to decrease following exercise, returning to values near those recorded prior to session one on day 3 (24). <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">These studies suggest that following a single session of resistance training, older exercisers will likely exhibit larger and longer changes in strength, ROM, swelling, DOMS, and higher creatine kinase concentrations. However, older exercisers may be as likely as younger exercisers to adapt to resistance training, as repeated sessions results in similar improvements in post-exercise outcome measures for all age groups.&#xA0;
<h3>Strange Finding: Adaptations Across Limbs</h3>
A study by Hody et al. compared 18 novice male exercisers (age: 22.9 &#xB1;1.8 years) 24 hours post-exercise following single-leg eccentric knee extensions on an isokinetic dynamometer with dominant and non-dominant legs, in random order, during separate sessions, 6 weeks apart. Participants completed 3 sets/session, 30 reps/set, short (0.5 min) rest between sets, and a moderate (60&#xB0;/sec) rep tempo. The findings demonstrated that 24 hours post-exercise, dominant and non-dominant knee extensions resulted in similar decreases in MVIC, increases in <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> stiffness, and increases in DOMS. However, despite using the other leg in the 2nd session, a significant reduction in the change in post-exercise outcomes measures was noted. This includes post-exercise serum concentrations of creatine kinase which exhibited similar elevations for dominant and non-dominant limbs 24 hours after the first session (1750.3 &#xB1; 2539.9 IU/L&#xAF;&#xB9;), and significant decreases in elevation following the 2nd session, using the other leg (347.3 &#xB1; 209.9 IU/L&#xAF;&#xB9;). This may imply that <a id="unilateral" data-tip="1551" target="_blank" href="/glossary-term/unilateral" class="glossary">unilateral</a> resistance training results in some adaptation of both limbs including a significant reduction in the elevation of creatine kinase concentrations following training of the other limb (39).

Recovery Time: Markers of Muscle Damage and Repeated Sessions

<h3>Summary:</h3>
<ul>
 <li>Lipid Profiles: Improvements in serum concentrations of total cholesterol and low-density lipoproteins (LDLs) are likely to be larger following resistance training 3x/week when compared to 1x/week, but 2x/week and 3/week may result in similar improvements. Further, resistance training frequency may not have an influence on serum concentrations of triacylglycerols and high-density lipoproteins (HDLs).</li>
 <li>Diabetes: Resistance training at least 2x/week is necessary to improve various serum concentrations (blood markers) associated with an increased risk of diabetes, and a frequency of 3x/week or 4x/week may further reduce risk.</li>
</ul>
<h3>Lipid Profiles</h3>
Several studies have compared lipid profiles following resistance training with various frequencies. Campa et al. compared 45 novice female exercisers (age: 50 &#xB1; 8.7 years) randomly assigned to a 1x/week group or 3x/week group. Participants completed a full body program (leg extensions and leg press, lat machine and low rows, pectoral machine and chest press, and shoulder press) for 24 weeks, 4 sets/exercise, 8-12 reps/set, 60-80% 1-RM, short (1 min) rest between sets, and moderate (2 min) rest between exercises. Results demonstrated that both groups exhibited similar improvements in blood pressure, triacylglycerols, and high-density lipoproteins (HDLs); however, only the 3x/week group exhibited significant improvements in low-density lipoproteins (LDLs), and total cholesterol (40). Pina et al. compared 39 novice female exercisers (age: &#x2265; 60 years) randomly assigned to a 2x/week group or a 3x/week group. Participants completed a full body program (chest press, leg press, rows, knee extensions, preacher curls, leg curls, tricep pushdowns, and calf raises) for 24 weeks, 1-2 sets/exercise, 10-15 reps/set, and a moderate rest between exercises (2-3 min). The findings demonstrated that although both groups exhibited similar and significant increases in HDLs, neither group exhibited significant changes in LDLs, very low-density lipoproteins (VLDL), or triglycerides (41). An RCT by Ihalainen et al. compared 92 novice exercisers (age: 65-75 years old) randomly assigned to a control group (no exercise), a 1x/week group, a 2x/week group, or a 3x/week group. All participants completed a 3-month familiarization period with a frequency of 2x/week, followed by 6 months of the experimental frequency. Resistance training included a full body program (leg press, knee extensions, knee curls, chest press, lat pulldowns, tricep pushdowns, ab curls, back extensions, rows, shoulder press, bicep curls, seated calf raise, and shoulder raise), 2-5 sets/exercise, and 4-12 RM/set. Results demonstrated that only the 3x/week group exhibited a significant decrease in LDLs and fat mass (42). Last, an <a id="observational-study" data-tip="1400" target="_blank" href="/glossary-term/observational-study" class="glossary">observational study</a> by Magalhaes et al. compared 31 experienced female exercisers (aged: 52.29 &#xB1; 4.56 years) who performed resistance training 3x or less/week, or more than 3x/week. Due to the observational design of this study resistance training parameters are unknown (exercises, sets, reps, intensity, rest between sets or exercises, and repetition tempo). The findings demonstrated that both groups exhibited similar changes in lipid profile (triacylglycerols, high-density lipoprotein, low-density lipoprotein, and total cholesterol) and metabolic phenotype (metabolically healthy or unhealthy) (43). These studies suggest that improvements in serum concentrations of total cholesterol and LDLs are likely to be larger following resistance training 3x/week when compared to 1x/week, but 2x/week and 3x/week may result in similar improvements. Further, resistance training frequency may not influence serum concentrations of triacylglycerols and HDLs.
<h2>Diabetes</h2>
Several of the studies mentioned previously have investigated the effect of resistance training frequency on risk factors associated with diabetes. The study mentioned above by Pina et al. compared 39 novice female exercisers (age: &#x2265; 60 years) randomly assigned to a 2x/week group or 3x/week group. The findings demonstrated that both groups exhibited similar decreases in inflammatory markers (C-reactive protein) and resting blood glucose during re-assessment at 24 weeks (41). Also mentioned above, the study by Campa et al. compared 45 novice female exercisers (aged: 50 &#xB1; 8.7 years) randomly assigned to a 1x/week group or 3x/week group. The findings demonstrated that the 3x/week group exhibited larger improvements in insulin resistance (fasting plasma glucose, insulin, HbA1c), and larger improvements on the Homeostasis <a id="model" data-tip="1469" target="_blank" href="/glossary-term/model" class="glossary">Model</a> <a id="assessment" data-tip="1478" target="_blank" href="/glossary-term/assessment" class="glossary">Assessment</a> for Insulin Resistance (HOMA-IR) (40). The RCT mentioned above by Ihalainen et al. compared 92 novice exercisers (aged: 65-75 years old) randomly assigned to a control group (no exercise), a 1x/week group, a 2x/week group, or a 3x/week group. Interestingly, when compared to pre-intervention values, only the 2x/week group exhibited a significant increase in hemoglobin A1c (HbA1c), and improvements on the HOMA-IR, homeostatic <a id="model" data-tip="1469" target="_blank" href="/glossary-term/model" class="glossary">Model</a> <a id="assessment" data-tip="1478" target="_blank" href="/glossary-term/assessment" class="glossary">Assessment</a> for &#x3B2;-cell function (HOMA-&#x3B2;), glucose, and insulin (42). Last, a retrospective <a id="observational-study" data-tip="1400" target="_blank" href="/glossary-term/observational-study" class="glossary">observational study</a> by Sawada et al. compared 10,680 experienced female exercisers (age: 57.8 &#xB1; 9.8 years) who regularly attended a fitness facility over a 5-month period. Participants were assigned to the first quartile (31.3 sessions, range of 1-41), second quartile (48.3 sessions, range of 42-54), third quartile (60.2 sessions, range of 55-66), and fourth quartile (80.5 sessions, range of 67-125). Participants completed a combined aerobic (aerobic step-ups) and resistance training program (chest press, seated rows, squats, shoulder press, lat pulldowns, leg extensions, leg curls, abdominal crunches, back extensions, &quot;lateral lift&quot;, bicep curls, tricep extensions, leg press, pec deck, &quot;oblique&quot;, hip abductors, hip adductors, and gluteal complex). The follow-up period was 5 years. Results demonstrated that an increase in exercise frequency resulted in lower incidence rates of diabetes (the 4th quartile had 23 cases, the 3rd quartile had 36 cases, the 2nd quartile had 49 cases, and the 1st quartile had 48 cases of diabetes), and a decreased incidence of a low body mass index (&lt; 22.7 kg/m&#xB2;) and low thigh circumference (&lt; 52.3 cm) (44). These studies suggest that resistance training at least 2x/week is necessary to improve various serum concentrations (blood markers) associated with an increased risk of diabetes, and a frequency of 3x/week or 4x/week may further reduce risk.
<ul></ul>

Frequency: Blood Serum Markers of Lipids, Diabetes, and General Health

Body Composition

Frequency: Body Composition and Older Adults

<h3>Summary:</h3>
<ul>
 <li>No Change in Body Composition: Resistance training alone (up to 3x/week) is not ideal for improving the body composition of novice adult exercisers.</li>
 <li>Similar Changes in Body Composition: Young adults may exhibit significant improvements in body composition following 8 - 10 weeks of a full-body resistance training program; however, the magnitude of body composition improvements may not be influenced by the frequency (days/week) of resistance training.&#xA0;&#xA0;</li>
 <li>Significant Differences in Body Composition: <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Young adults are likely to exhibit larger improvements in body composition when comparing resistance training 4x or more/week to 3x or less/week. Note, the studies in this section included resistance training programs with significantly larger exercise volumes than those described in previously mentioned studies.&#xA0;</li>
</ul>

<h3>No Change in Body Composition</h3>
A study by Lee et al. compared 17 novice female exercisers (age: 20-24 years) randomly assigned to a 1x/week group or a 3x/week group. Participants performed a full body program (squats, bench press, bicep curls, sit-ups, lat pulldowns, shoulder press, and leg extensions) for 12 weeks, 3 sets/exercise, 10 reps/set, with 60% 1-RM loads. The findings demonstrated that none of the participants exhibited significant changes in body composition (body weight, <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> mass, fat mass percentage, and abdominal fat mass percentage) (57). This study may imply that resistance training alone (up to 3x/week) is not ideal for improving the body composition of novice adult exercisers.
<h2>Similar Changes in Body Composition</h2>
Additional studies demonstrate that resistance training may be beneficial for improving body composition; however, the frequency of resistance training may not have a significant effect on the magnitude of change. An RCT by Arazi et al. compared 39 novice male exercisers (age: 20.33 &#xB1; 1.8 years) who were randomly assigned to a control group (no exercise), or groups performing resistance training 1x/week, 2x/week, or 3x/week. Note, the 1x/week group completed a full body program during each session, the 2x/week group completed one upper and lower body session/week, and the 3x/week group completed two upper and one lower body session/week. All participants completed the same exercises (leg press, leg curls, leg extensions, calf raises, lat pulldowns, rows, bench press, peck flys, bicep curls, dumbbell bicep curls, tricep press downs, and tricep extensions) for 8 weeks, sets were matched for weekly volume, 6-12 reps/set, 60-80% 1-RM loads (periodization), and a moderate (2-3 min) rest period. The findings demonstrated that all groups exhibited significant and similar increases in body weight and decrease in body fat percentage (58). Hoffman et al. compared 61 male collegiate football athletes (age: 20.1 &#xB1; 1.5 years) randomly assigned to groups performing resistance training 3x/week, 4x/week, 5x/week, or 6x/week, with all participants completing an additional 2x/week of conditioning. All participants completed a split routine for 10 weeks, 4-5 sets/exercise, 2-10 reps/set for large movements (squats, lunges, deadlifts, bench press, and push press), 3 sets/exercise of 10 reps/set for all other exercises (dumbbell bench press, incline bench press, dumbbell incline flys, variable resistance machine flys, variable resistance machine decline press, push press, behind neck press, military press, upright rows, dumbbell shoulder press, dumbbell raises to the side and front, variable resistance machine <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> raises, variable resistance machine overhead press, tricep pushdowns, tricep dumbbell extensions, lying tricep extensions, close-grip bench press, dips, tricep kickbacks, 4-way neck machine, squats, lunges, leg press, hack squat, leg extensions, leg curls, calf raises, deadlifts, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> cleans, lat pulldowns, low cable rows, bent over rows, dumbbell rows, variable resistance machine pullovers, pullups, EZ bar curls, dumbbell curls, barbell curls, wrist curls and reverse wrist curls). Results demonstrated that the higher frequency groups exhibited larger improvements in strength; however, all groups exhibited similar improvements in body composition (59). These studies suggest that young adults may exhibit significant improvements in body composition following 8 - 10 weeks of a full-body resistance training program; however, the magnitude of body composition improvements may not be influenced by the frequency (days/week) of resistance training.&#xA0;
<h2>Significant Differences in Body Composition</h2>
Several studies demonstrate that young adults performing higher frequency resistance training may exhibit significantly larger improvements in body composition. An RCT by Serra et al. compared 48 male and 36 female novice exercisers (age: 30-45 years) who were randomly assigned to a control group (no exercise), 2x/week group, 3x/week group, or 4x/week group. Participants completed a full body program (wide-grip front lat pulldowns, leg press, machine chest press, leg extensions, rows, leg curls, shoulder press, and abdominal crunches) for 3 months, 3 sets/exercise, 10-12 RM/set, and moderate (1-1.5 min) rest between sets and exercises. The findings demonstrated that none of the groups exhibited significant changes in <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> mass or waist circumference; however, all groups exhibited similar increases in wide-grip lat pulldown, machine chest press, and leg press 10-RM strength. Only the 4x/week group exhibited a significant reduction in body fat percentage (60). Kraemer et al. compared 44 male collegiate football athletes (age: 19.9 &#xB1; 4.3 years) randomly assigned to a 3x/week group, or a 4x/week group, for 24 weeks. The 3x/week group completed a full body circuit training routine (leg press, bench press, leg curls, rows, calf raises, bicep curls, sit-ups, pullovers, military press, &quot;abduction and adduction exercises&quot;, knee extensions, chest flys, leg curls, <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> raise, seated calf raises, tricep pushdowns, back hyperextensions, upright rows, rotator cuff exercises, and lat pulldowns), 1 set/exercise, 8-12 RM/set, and moderate (1-2 min) rest between exercises. The 4x/week group completed a full body daily-undulating periodized routine (hang clean/power cleans squats, split squats, bench press, push press, rotator cuff exercises, leg curls, sit-ups, leg press, upright rows, dumbbell military press, bicep curls, tricep pushdowns, lat pulldowns, seated rows, side-bends, &quot;obliques&quot;, calf raises, and lunges), 2-5 sets/exercise, 3-15 RM/set, and moderate to long rest interval (1-4 minutes, the study did not clarify if this was between sets or exercises). Results demonstrated that the 4x/week group exhibited significantly larger increases in performance and larger improvements in body composition (decreased body fat percentage and increased body mass). Note, results could have been influenced by exercise selection (i.e. - only 4x/week completed hang or <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> cleans and squats), as well as differences in routine and program design (e.g. circuit versus horizontal loading, periodizations, etc.) (61). Last, a<span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">n RCT by Marx et al. compared 34 female (aged: 22.6 &#xB1; 3.7 years) novice exercisers who were randomly assigned to a control group (no exercise), 3x/week group, or 4x/week group. Participants who exercised 3x/week completed circuit-style training (leg press, bench press, leg curls, rows, standing calf raises, bicep curls, sit-ups, pullovers, military press, hip abduction/adduction, knee extensions, chest fly, leg curls, <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> raises, seated calf raises, tricep pushdowns, back extensions, upright rows, rotator cuff exercises, and lat pulldowns) with 1 set/exercise, 8-12 reps to failure/set, a moderate (1-2 min) rest between exercises, and a slow (4:0:2) rep tempo. Participants who exercised 4x/week completed a 2-day split routine (Day 1: hang cleans, squats, bench press, push press, leg curls, sit-ups, rotator cuff exercises; Day 2: upright rows, DB military press, bicep curls, tricep pushdowns, lat pulldowns, seated rows, sit-ups, side bends, <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> hip flexions, leg curls, calf raises and lunges) with 2-4 set/exercise, 3-15 reps/set (undulating periodization), and moderate to long rest between sets (1-4 minutes). The finding demonstrated that the 4x/week group exhibited significantly larger improvements in performance and body composition (decreased body fat % and increased fat-free mass) (1). These studies demonstrate that young adults are likely to exhibit larger improvements in body composition when comparing resistance training 4x or more/week to 3x or less/week. Note, the studies in this section included resistance training programs with significantly larger exercise volumes than those described in previously mentioned studies.

Frequency: Body Composition and Young Adults

<h3>Summary</h3>
<ul>
 <li>No Change in Body Composition:
 <ul>
 <li>3-6 sets/exercise/week and 12-24 weeks of training: Young and elderly adult exercisers performing 12 -24 weeks of resistance training, with a training volume of 3-6 sets/muscle group/week, regardless of the training frequency (1-3x/week), are unlikely to exhibit significant changes in body mass, body mass index, fat mass, skinfold thickness, or waist and limb circumference.</li>
 <li>9-12 sets/exercise/week and 6-8 weeks of training: Body composition changes may not be significant following 6-8 weeks of resistance training, even with relatively high volumes (9-12 sets/exercise/week) and frequencies (2-6x/week).&#xA0;</li>
 </ul>
 </li>
 <li>Similar Improvements in Body Composition: A relatively high volume of resistance training (10 - 12 sets/muscle group/week for 4 - 20 weeks) may result in significant improvements in body composition; however, when resistance training volume is equated, the frequency may not significantly affect outcomes.</li>
 <li>Significant Differences in Changes in Body Composition: <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">When sets/muscle group are equated during relatively high-volume resistance training, training frequency may have a significant influence on the amount of body composition improvement. It could be hypothesized that 2-3x/muscle group/week (depending on the volume of each session) is the ideal frequency for optimizing total reps/session or total load lifted (reps x load/week), resulting in larger total volumes of exercise, larger increases in <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> mass, and more total calories burned.</li>
</ul>
<h3>No Change in Body Composition</h3>
3-6 sets/exercise/week and 12-24 weeks of training
Several studies suggest that the addition of a resistance training routine alone may not be sufficient to result in a significant change in body composition, even when comparing resistance training frequencies of 1 - 3x/week. An RCT by Ramirez-Campillo et al. compared 24 novice female exercisers (age: 60-83 years) who were randomly assigned to a control group (no exercise), a 2x/week group, or a 3x/week group. Participants completed a full body program (bench press, upright rows, bicep curls, leg extensions, squats, crunches, and supermans) for 12 weeks, 8 reps/set, 75% 1-RM loads, short (1 min) rest between sets, and a moderate (3:0:MaxV) rep tempo. Volume was equated; the 2x/week group performed 3 sets/exercise, and the 3x/week group performed 2 sets/exercise. The findings demonstrated that neither group exhibited significant changes in body composition (body mass and body mass index) (62). McLester et al. compared 18 experienced exercisers (age: 24.7 &#xB1; 3.1 years) randomly assigned to a 1x/week group or a 3x/week group. All participants completed a full body program (bench press, triceps press, <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> arm raises, lat pulldowns, bicep curls, leg press, knee extensions, leg curls, and calf raises) for 12 weeks, 3-10 RM/set, and moderate rest between sets (2-min). The volume of the routines was equated; the 1x/week group completed 3 sets/exercise, and 3x/week group completed 1 set/exercise. The findings demonstrated that neither group exhibited significant changes in body composition (body mass, skinfold thickness, body fat %, as well as upper arm, abdomen, thigh, and calf circumference) (63). <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Fortes et al. compared 36 experienced male exercisers (age: 18-30 years) randomly assigned to groups performing resistance training 1x/week, 2x/week, or 3x/week. All participants completed a full-body program (bench press, leg press, seated rows, squats, shoulder press, and leg curls) for 24 weeks. The volume of the routines was equated, the 1x/week group performed 6 sets/exercise, the 2x/week group performed 3 sets/exercise, and 3x/week group performed 2 sets/exercise. All groups performed 10 RM/set, and moderate (2 min) rest between sets and exercises. The results demonstrated that none of the groups exhibited a significant change in body composition (non-fat mass, fat mass, and total body mass) (64). These studies suggest that young and elderly adult exercisers performing 12 -24 weeks of resistance training, with a training volume of 3-6 sets/muscle group/week, regardless of the training frequency (1-3x/week), are unlikely to exhibit significant changes in body mass, body mass index, fat mass, skinfold thickness, or waist and limb circumference.
9-12 sets/exercise/week and 6-8 weeks of training
Additional volume-equated studies comparing training frequency have incorporated larger volumes of exercise, but shorter training durations; and again, failed to demonstrate a significant change in body composition. Hunter compared 46 participants (age: 24 &#xB1; 4 years) with unknown exercise experience randomly assigned to a 3x/week group or a 4x/week group. All participants completed a full body program (bench press, squats, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> cleans, behind-the-neck press, two hand curls, behind-the-neck pulldowns, and knee curls) for 7 weeks, with 7-10 reps/set. Volume was equated with&#xA0;the 3x/week group performing 3 sets/exercise, and the 4x/week group performing 2-3 sets/exercise. Neither group exhibited significant changes in body composition (body weight, body fat percentage, lean body mass, waist circumference, or hip circumference) (65). <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Benton et al. compared 21 novice female exercisers (age: 40-55 years) who completed a resistance training program with a self-selected frequency of 3x/week or 4x/week. All participants performed resistance training exercises for the entire body (chest press, latissimus pulldowns, shoulder press, seated rows, biceps curls, triceps pushdowns, leg press, leg extensions, and leg curls) for 8 weeks, 8-12 reps/set, and 80% 1-RM loads. The 3x/week group performed 3 sets/exercise during each session, and the 4x/week group performed all 3 sets/upper body exercise 2x/week, and 6 sets/lower body exercise 2x/week. Results demonstrated similar increases in strength and total lean mass; however, neither group exhibited changes in body mass index (BMI), waist circumference, hip circumference, total fat mass, or body fat percentage (66). Last, Colquhoun et al. compared 28 experienced male exercisers (aged: 18-30 years) randomly assigned to a 3x/week group or a 6x/week group. Participants completed a full body program (squats, bench presses, deadlifts, as well as exercises for rhomboids, latissimus dorsi, deltoids, biceps, triceps, and abdominals) for 6 weeks, and 3-8 RM/set. The 3x/week group performed 4-sets/exercise/session, and 6x/week group performed 2-sets/exercise/session (volume equated). Results demonstrated similar improvements in strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, and similar increases in lean mass and total body mass; however, neither group exhibited significant changes in fat mass or body fat percentage (67). These studies imply that body composition changes may not be significant following 6-8 weeks of resistance training, even with relatively high volumes (9-12 sets/exercise/week) and frequencies (2-6x/week).&#xA0;&#xA0;
<h3>Similar Change:</h3>
Two volume-equated studies demonstrated that relatively high-volume resistance training resulted in significant improvements in body composition; however, frequency did not significantly affect outcomes. An RCT by Calder et al. compared 30 females with unknown exercise experience (age: 20.7 &#xB1; 1.3 years) randomly assigned to a control group (no exercise), a 2x/week group, or a 4x/week group. Participants completed a full body program (bench press, lat pulldowns, tricep extensions, bicep curls, leg press, knee extensions, and leg curls) for 20 weeks, 5 sets/exercise, 6-12 RM/exercise, and moderate (2 min) rest between sets. The 2x/week group completed all exercises each session, and the 4x/week group completed two upper body sessions and two lower body sessions each week. Note, all participants were college students who performed the 20 weeks of training in two 10-week sessions separated by a 2-week winter break. Results demonstrated that both groups exhibited similar increases in strength, increases in whole body lean tissue, and similar decreases in body fat percentage; however, neither group exhibited a significant change in trunk lean tissue mass or whole body fat mass (68). Ribeiro et al. compared 10 male bodybuilders (aged: 26 &#xB1; 2.7 years) randomly assigned to a 4x/week group or a 6x/week group. Note, both groups exercised each <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> group 2x/week. Participants completed the same exercises as part of a 2-day or 3-day split routine (bench press, incline dumbbell flys, cable crossovers, barbell military press, <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> raises, lying triceps French press, triceps pushdowns, standing calf raises, seated calf raises, crunches, cable crunches, v-bar pulldowns, bent over barbell rows, seated cable rows, arm curls, alternate incline dumbbell curls, seated palm-up wrist curls, seated palm-down barbell wrist curls, squats, leg extensions, lying leg curls, oblique crunches, and seated leg tucks) for 4 weeks, 4 sets/exercise, 6-12 reps to failure/set (pyramid sets 12, 10, 8, and then 6 reps/set), moderate (1-2 min) rest between sets, long (2-3 min) rest between exercises, and a rep tempo ratio of 2:1 (eccentric to concentric). Note, this study controlled for diet so that each participant ingested 54.9 &#xB1; 3.5 kcal/kg of body mass, with 1.8 g/kg from protein intake, approximately 76% of calories from carbohydrates, and approximately 13% from lipids. Further, all food/meals were prepped and delivered to participants. Results demonstrated similar improvements in strength and body composition (increased body mass, relative body fat percentage, and fat-free mass) (69). These studies demonstrate that a relatively high volume of resistance training (10 - 12 sets/muscle group/week for 4 - 20 weeks) may result in significant improvements in body composition; however, when resistance training volume is equated, the frequency may not significantly affect outcomes.
<img alt="How many times to work a muscle group per week?" title="2-3 times per muscle group per week may be the ideal frequency to exhibit body composition changes" src="https://www.datocms-assets.com/25800/1682898639-istock-1295663502.jpg">
<ul></ul>
Significant Difference
The remaining studies demonstrate that even when the number of sets is equated, the frequency of resistance training may have some influence on body composition improvements. Yue et al. compared 18 experienced male exercisers (age: 28 &#xB1; 7.9 years) randomly assigned to a group performing 2 sessions/week with 4 sets/exercise, or a group performing 4 sessions/week with 2 sets/exercise (volume equated). All participants completed a full body program (bench press, dumbbell flys, chest press, barbell curls, seated dumbbell curls, reverse grip bent-over rows, dumbbell deltoid raises, barbell shoulder press, barbell shoulder front raises, <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> pulldowns, dumbbell reverse flys, barbell pullovers, barbell lying arm extensions, barbell close grip bench press, cable pushdowns, parallel squats, deadlifts, and machine leg curls) for 6 weeks, 8-12 reps/set, 75% 1-RM loads, and moderate (2-min) rest between sets. Results demonstrated that both groups exhibited similar increases in strength, <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> thickness, and fat-free mass. Neither group exhibited significant changes in total body mass or total fat mass; however, the 2x/week group exhibited a significant decrease in body fat percentage (70). <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Pina et al. compared 47 females (aged: 65 &#xB1; 4 years) randomly assigned to a 2x/week group or a 3x/week group. All participants completed a full body program (chest press, knee extensions, lat pulldowns, leg curls, preacher Scott curls, seated calf raises, tricep pushdowns, and crunches) for 12 weeks, 10-15 reps to failure/set (note: 15-20 reps to failure/set for calf raises, and 20-30 reps/set for crunches), moderate rest between sets (1-2 min), moderate rest between exercises (2-3 min), and a rep tempo ratio of 2:1 (eccentric to concentric). Volume was equated; the 2x/week group performed 3 sets/exercise, and the 3x/week group performed 2 sets/exercise. Both groups exhibited similar increases in lean soft tissue, with no significant change in body mass; however, only the 3x/week group exhibited a significant decrease in body fat mass and body fat percentage (71). These studies may imply that when sets/muscle group are equated during relatively high-volume resistance training, training frequency may have a significant influence on the amount of body composition improvement. It could be hypothesized that 2-3x/muscle group/week (depending on the volume of each session) is the ideal frequency for optimizing total reps/session or total load lifted (reps x load/week), resulting in larger total volumes of exercise, larger increases in <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> mass, and more total calories burned.

Frequency: Body Composition and Volume-equated Routines

Hypertrophy

<h3>Summary</h3>
<ul>
 <li>Hypertrophy: <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">The research available introduces confounding variables including the effects of isotonic versus concentric contractions and the frequency of sessions versus the total number of sessions. However, it may be implied that performing a session type (concentric, isotonic, isometric, etc) just 1x/week (or less) is insufficient to result in significant <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> changes (type II <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> hypertrophy and proportion changes); and conversely, more than 2x/week may not result in additional benefits.</li>
 <li>Muscle Fiber Damage: <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Resistance training results in far more type IIa and type IIx than type I <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">Muscle Fiber</a> damage, which may partially explain why resistance training results in much larger changes in type II <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">Muscle Fiber</a> size and proportion. Further, <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">Muscle Fiber</a> damage following the 1st session of a new resistance training routine will likely result in significantly more <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">Muscle Fiber</a> damage than a 2nd session of a similar routine, suggesting significant adaptations to resistance training occurs within days of the 1st session.</li>
</ul>
<h3>Hypertrophy</h3>
Two studies have compared resistance training frequency and its effect on <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> size and proportion. Stec et al. compared 64 male and female (aged: 65.5 &#xB1; 3.6 years) novice exercisers who were randomly assigned to groups performing: 2x/week with isotonic repetitions, 3x/week with isotonic repetitions, 2x/week with a combination of isotonic and concentric only reps (1x/week of isotonic, 1x/week of concentric only), or 3x/week with a combination of isotonic and concentric only reps (2x/week of isotonic, 1x/week of concentric only). Participants completed a full body program (squats, knee extensions, leg press, heel raises, seated overhead press, chest press, seated cable rows, pulldowns, bicep curls, tricep pushdowns, and abdominal flexion) for 30 weeks, 1-2 sets/exercise, and 10-15 reps near failure/set. The findings demonstrated that all groups exhibited similar increases in leg press, knee extension, chest press, overhead press, and arm curl 1-RM strength; however, the 2x/week combination group achieved at 24 weeks what other groups achieved in 8 weeks. The findings also demonstrated that body composition (increased total body lean mass, increased thigh <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> mass, increased arm mass, and decreased body fat %) improved most for the 3x/week groups, a significant change was exhibited by the 2x/week of isotonic exercise groups, and body composition changes were not significant for the 2x/week combination group. Additionally, the findings demonstrated that both 3x/week groups, and the 2x/week of isotonic exercise groups exhibited similar increases in <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> cross-sectional area (CSA) (no change in type I fibers, similar increases in type II fibers), and a similar shift in type IIx fibers to IIa fibers. The 2x/week combination group did not exhibit a significant change in CSA or shift in fiber type ratio (2). Carroll et al. compared 17 novice exercisers (aged: 18.8 &#xB1; 1.7 years) randomly assigned to a 2x/week group, or a 3x/week group. Note, all participants completed 18 sessions; the 2x/week group completed the intervention in 9 weeks, and the 3x/week group completed the intervention in 6 weeks. All participants completed a full body program (half squats, leg extensions, leg curls, bench press, lat pulldowns, <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> raises, and abdominal crunches), 3 sets/exercise, 4-10 RM/set, (except crunches performed 5-20 RM/set), and a moderate (3-min) rest between sets and exercises. The findings demonstrated that both groups exhibited similar improvements in squat 1-RM strength and isokinetic leg extension strength at 1.05 rad/sec. However, the 2x/week group exhibited larger increases in isometric leg extension strength, isokinetic leg extension strength at 3.14, 5.24, and 8.73 rad/sec, and a larger increase in the<span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;"> proportion of type IIa <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> fibers (72). <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Unfortunately, these studies introduce confounding variables including the effects of isotonic versus concentric contractions and the frequency of sessions versus the total number of sessions. However, it may be implied that performing a session type (concentric, isotonic, isometric, etc) just 1x/week (or less) is insufficient to result in significant <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> changes (type II <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> hypertrophy and proportion changes); and conversely, more than 2x/week may not result in additional benefits.
<span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;"><img alt="Muscle fiber types may change based on training" title="Type I and Type II muscle fibers in a staining of a muscle cross section" src="https://www.datocms-assets.com/25800/1632846078-muscle-fiber-types.jpg">
<h3>Muscle Fiber Damage</h3>
Two additional studies investigated the recovery rate of damaged <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> fibers following resistance training. Macaluso et al. compared 8 novice male exercisers (age: 22 &#xB1; 1 year) 6 hours, 1 day, 2 days, and 3 days post-exercise. Participants completed jump squats without load for 10 sets, 10 reps/set, short (1 min) rest between sets, and an explosive rep tempo. The findings demonstrated that standing and squatting quadriceps <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> soreness significantly increased following exercise, peaked 1- 2 days post-exercise, and returned to pre-exercise values 3 days post-exercise. Additionally, <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> biopsy demonstrated that 9.6% of <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> fibers were damaged (155 fibers were damaged out of 1,616), and within subgroups of damaged <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> fibers, 14.3% of type IIx fibers, 10.3% of type IIa fibers, and 7.6% of type I fibers. The damaged fibers had lower <a id="mitochondria" data-tip="1255" target="_blank" href="/glossary-term/mitochondria" class="glossary">mitochondrial</a> volume, and thinner <a id="z-disk" data-tip="1333" target="_blank" href="/glossary-term/z-disk" class="glossary">Z disks</a> compared to undamaged fibers, and <a id="sarcomere" data-tip="1323" target="_blank" href="/glossary-term/sarcomere" class="glossary">sarcomere</a> damage was exhibited by 85.7% of type IIx fibers, 84.0% of type IIa fibers, and 26.7% of type I fibers (73). Hortob&#xE1;gyi et al. compared 9 male and 9 female novice exercisers (age: 22.6 &#xB1; 2.7 years) 2 days, 4 days, and 7 days post-exercise. Participants were randomly assigned to an exercise or control (no exercise) group, and the exercise group completed 2 sessions separated by 2 weeks. The exercise protocol included eccentric knee extensions, 10 sets/exercise, 10 reps/set, 80% of 1-RM loads, and long (3 min) rest between sets. The findings demonstrated that following the first session, exercisers exhibited significant decreases in dynamic, isokinetic, and isometric strength, and increases in DOMS, with peak changes noted 2-days post-exercise, dynamic strength returning to near pre-exercise values 4 days post-exercise, and isokinetic strength, isometric strength, and DOMS remaining slightly but significantly different from pre-exercise values 7 days post-exercise (last day of re-assessment). <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Following the second session, changes in strength and DOMS failed to reach statistical significance. Additionally, following the 1st session, significant <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> damage (&quot;disorganization&quot; of myofilaments, sarcomeres, and Z-lines) was present 2 days post-exercise and returned to near normal 7 days post-exercise. Following the 2nd session a similar trend was noted; however, the magnitude of damage was less (65 &#xB1; 12% of pixels compared to 23 &#xB1; 4% of pixels 2 days post-exercise) (37). These studies suggest that resistance training results in far more type IIa and type IIx than type I <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> damage, which may partially explain why resistance training results in much larger changes in type II <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> size and proportion. Further, <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> damage following the 1st session of a new resistance training routine will likely result in significantly more <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> damage than a 2nd session of a similar routine, suggesting significant adaptations to resistance training occurs within days of the 1st session.

Frequency and Recovery Time: Hypertrophy and Muscle Fiber Changes

Frequency and Recovery Time: Hypertrophy and Older Exercisers

Frequency: Hypertrophy, Young Adults, and Volume Equated Studies

<h3>Summary</h3>
<ul>
 <li>Complex Programs: Two studies compared 8 and 24 weeks of resistance training, with a frequency of 3x/week or 4x/week and more complex program designs; however, this complexity introduces several confounding variables. Both studies demonstrated a significant increase in <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> hypertrophy for all training frequencies and programs, which may <a id="base-of-support" data-tip="1197" target="_blank" href="/glossary-term/base-of-support" class="glossary">support</a> the increase in complexity but also suggests additional research is needed to isolate variables and the implicated change in outcomes. Additional implications include larger improvements in hypertrophy resulting from the performance of fewer high-quality sets/routines, <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> groups are not targeted on consecutive days, the inclusion of higher-intensity training (heavier loads and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training), and the periodization of acute variables (load, reps, sets, etc.).&#xA0;</li>
 <li>Menstrual Cycle Adjusted Programs: Based on the study Wikstron-Frisen (2017), larger improvements in lower extremity hypertrophy may result from performing higher volume training (5x/week) during the first 2 weeks of the menstrual cycle than performing higher volume training during the second 2 weeks.</li>
 <li>Adolescent Athletes: A study by DeRenne et al. (1996) may imply that adolescents participating in organized sports following a pre-season resistance training program may exhibit larger increases in hypertrophy with an in-season resistance training frequency of 2x/week, when compared to 1x/week.</li>
 <li>Additional Findings: An 8-week program of leg extensions, regardless of training frequency (2, 3, or 5x/week), may be insufficient to result in lower extremity hypertrophy. Further, increases in hypertrophy may be similar following resistance training programs with a frequency of 2x/week or 3x/week, but significantly less for 1x/week.&#xA0;</li>
</ul>
<h3>Complex Programs</h3>
Two studies included in this review involve more complex resistance training programs; as might be expected in college sports and professional athletic settings. An RCT by Firoozi et al. compared 33 experienced male exercisers (age: 21.9 &#xB1; 1.3 years) randomly assigned to a control group (no exercise), a 3x/week group, or a 4x/week group. Participants completed a split routine (exercises included in the program: squats, knee extensions, barbell bench press, barbell incline bench press, dumbbell bench press, barbell arm curls, dumbbell arm curls, arm curls with EZ bar, military press, behind the head military press, dumbbell <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> raises, dumbbell tricep extensions, lying close grip triceps press, incline triceps extensions, deadlifts, leg curls, leg press, dumbbell lunges, calf raises, lat pulldowns behind the head, barbell rear delt rows, rear deltoid rows, hyperextensions, and abdominal crunches) for 8 weeks, 3 sets/exercise, 8 reps/set, 65-80% of 1-RM loads (periodized), moderate (1-1.5-min) rest between sets, and moderate (2-3 min) rest between exercises. Volume was equated by the total number of exercises performed per session, with each group performing the same exercises. The 3x/week group performed more exercises per routine - Day 1: legs, chest, and biceps; Day 2: shoulders, triceps, and legs; Day 3: legs, back, and core. The 4x/week group performed fewer exercises per routine - Day 1: legs and arms; Day 2: legs and chest; Day 3: legs and shoulders, Day 4: back, legs, and core. Results demonstrated neither group exhibited a significant change in bench press or leg press endurance (reps to failure with 60% 1-RM). Both groups exhibited significant improvements in 1-RM strength, but the 3x/week group exhibited significantly larger increases in bench press and leg press 1-RM strength. Additionally, the 3x/week group exhibited significantly larger increases in thigh circumference; however, the 4x/week group exhibited significantly larger increases in chest circumference. The results of this study are puzzling due to the way the exercises were split throughout the routines; for example, the legs and arms are included every day of both programs, but <a id="specificity" data-tip="1224" target="_blank" href="/glossary-term/specificity" class="glossary">specific</a> exercises for the chest, back, and shoulder are only included 1 day each week. This study may suggest that performing fewer high-quality sets (and exercises) is more beneficial for upper body training (upper body program for 4x/week group), and that training similar <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> groups on consecutive days is deleterious to hypertrophy (lower body program for 4x/week group) (94). Kraemer et al. compared 44 male collegiate football athletes (age: 19.9 &#xB1; 4.3 years) randomly assigned to a 3x/week group, or a 4x/week group, for 24 weeks. The 3x/week group completed a full body circuit training routine (leg press, bench press, leg curls, rows, calf raises, bicep curls, sit-ups, pullovers, military press, &quot;abduction and adduction exercises&quot;, knee extensions, chest flys, leg curls, <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> raises, seated calf raises, tricep pushdowns, back hyperextensions, upright rows, rotator cuff exercises, and lat pulldowns), 1 set/exercise, 8-12 RM/set, a moderate rest between exercises (1-2 min). The 4x/week group completed a full body daily-undulating periodized routine (hang clean/power cleans squats, split squats, bench press, push press, rotator cuff exercises, leg curls, sit-ups, leg press, upright rows, dumbbell military press, bicep curls, tricep pushdowns, lat pulldowns, seated rows, side-bends, &quot;obliques&quot;, calf raises, and lunges), 2-5 sets/exercise, 3-15 RM/set, and moderate to long rest interval (1-4 minutes, the study did not clarify if this was between sets or exercises). Results demonstrated that the 4x/week group exhibited significantly larger increases in 1RM strength, strength endurance, and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, and larger improvements in body composition (decreased body fat percentage and increased body mass). Note, results could have been influenced by exercise selection (i.e. only the 4x/week group completed hang cleans, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> cleans, and squats), as well as differences in routine and program design (e.g. circuit versus horizontal loading, periodizations, etc.) (61). These two studies compared 8 and 24 weeks of resistance training, with a frequency of 3x or 4x/week and more complex program designs; however, this complexity introduces several confounding variables. Both studies demonstrated a significant increase in <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> hypertrophy for all training frequencies and programs, which may <a id="base-of-support" data-tip="1197" target="_blank" href="/glossary-term/base-of-support" class="glossary">support</a> the increase in complexity but also suggests additional research is needed to isolate variables and the implicated change in outcomes. Additional implications include larger improvements in hypertrophy resulting from the performance of fewer high-quality sets/routines, ensuring similar <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> groups are not targeted on consecutive days, the inclusion of higher intensity training (heavier loads and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training), and the periodization of acute variables.&#xA0;
<h3>Menstrual Cycle-Adjusted Programs</h3>
One study was located that compared outcomes following changes in resistance training frequency based on the menstrual cycle. An RCT by Wikstrom-Frisen et al. compared 59 experienced female exercisers (age: 24.5 &#xB1; 2.6 years) randomly assigned to a control group (leg training 3x/week), to group A (leg training 5x/week during the first two weeks of each cycle and 1x/week during the second 2 weeks of the cycle), or group B (leg training 1x/week during the first two weeks of each cycle and 5x/week during the second 2 weeks of the cycle). Leg training (leg press and leg curls) was performed for 16 weeks, 3 sets/exercise, 8-12 RM/set, with a moderate (1-2 min) rest between sets. Note, participants were able to complete upper-body resistance training as desired. The findings demonstrated that the use of oral contraceptives did not have an effect on outcomes. Only the control group and group A exhibited significant increases in <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> and right knee extension peak torque; however, all groups exhibited similar increases in left knee peak <a id="torque" data-tip="1294" target="_blank" href="/glossary-term/torque" class="glossary">torque</a>. Interestingly, only group A exhibited significant increases in lower body lean mass (95). Based on this study, larger improvements in lower extremity hypertrophy may result from performing higher volume training (5x/week) during the first 2 weeks of the menstrual cycle than performing higher volume training during the second 2 weeks.
<h3>Adolescent Athletes</h3>
One study compared adolescents performing resistance training with varied frequency during a sporting season. DeRenne et al. compared 21 male baseball athletes (age: 13.25 &#xB1; 1.26 years) who were novice exercisers, following a pre-season protocol, and during the season, random assignment to a 1x/week group or a 2x/week group. All participants completed a full-body resistance training program (bench press, wide-grip cable pulldowns, leg extensions, leg curls, bicep curls, tricep extensions, rotator cuff exercises, wrist curls, and wrist extensions). All participants performed the pre-season program for 12 weeks, 3x/week, 3 sets/exercise, 10 reps/set, with 50-100% of 10-RM loads. Participants were then randomly assigned to a 1x/week group or 2x/week group for 12 weeks during the season, 3 sets/exercise, 10 reps/sets, and 50-75% 10-RM loads. The findings demonstrated that neither group exhibited a change in leg press 10-RM strength and pull-ups to failure following pre-season training, and only the 1x/week group exhibited a significant increase in bench press 10-RM strength during the season. Neither group exhibited significant changes in chest, bicep, waist, or thigh girth; however, the 2x week group, exhibited a significant increase in calf girth, lean body mass, and a decrease in 7-site skinfold thickness (3). This study may imply that adolescents participating in organized sports following a pre-season resistance training program may exhibit larger increases in hypertrophy with an in-season resistance training frequency of 2x/week when compared to 1x/week.
<h3>Additional Findings</h3>
Two additional studies reinforce some of the findings discussed in previous sections. An RCT by Barcelos et al. compared the legs of 20 novice male exercisers (age: 23 &#xB1; 4 years). All exercisers performed leg extensions 5x/week with one leg, and the other leg was randomly assigned to a 2x/week or 3x/week protocol. All participants performed the leg extension protocol for 8 weeks, 3 sets/session, 9-12 RM/set, 80% 1-RM loads, and moderate (2-min) rest between sets. The findings demonstrated that all legs exhibited a similar increase in <a id="unilateral" data-tip="1551" target="_blank" href="/glossary-term/unilateral" class="glossary">unilateral</a> knee extension 1-RM strength and similar increases in vastus lateralis CSA. Note, the 5x/week resulted in significantly more total training volume when compared to the 2x/week or 3x/week protocol (96). A large <a id="observational-study" data-tip="1400" target="_blank" href="/glossary-term/observational-study" class="glossary">observational study</a> by Westcott et al. compared 1,619 participants (age: 21-80 years, the study did not disclose exercise experience) randomly assigned to a 1x/week group, 2x/week group, or 3x/week group. Participants completed a full body program (leg extensions, leg curls, &quot;double chest&quot;, &quot;back pullover&quot;, <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> raises, bicep curls, tricep extensions, abdominal curls, back extensions, neck flexions, and neck extensions) for 10 weeks, 1 set/exercise, 8-12 RM/set, and a slow (4:0:2) rep tempo. The findings demonstrated that the 2x/week group and 3x/week group exhibited similar increases in lean mass, which were significantly more than the 1x/week group (56). These studies imply that an 8-week program of leg extensions, regardless of training frequency (2, 3, or 5x/week), may be insufficient to result in lower extremity hypertrophy. Further, increases in hypertrophy may be similar following resistance training programs with a frequency of 2x/week or 3x/week, but significantly less for 1x/week.&#xA0;
<ul></ul>

Frequency: Additional Hypertrophy Findings

Strength, Power, and Delayed Onset Muscle Soreness (DOMS)

<h3>Summary</h3>
<ul>
 <li>1x/week versus 2x/week: Older exercisers may initially (9-12 weeks) exhibit a similar increase in strength from resistance training 1x/week or 2x/week; and after the initial period, 1x/week may be sufficient to maintain or increase strength. However, research also suggests that lower body <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> may require a minimum frequency of 2x/week.</li>
 <li>2x/week versus 3x/week: Older exercisers may not see significant differences in strength when comparing 12 - 24 weeks of resistance training with a&#xA0; frequency of 2x/week or 3x/week, including similar rates of strength loss when followed by a detraining period. However, the increase in chest press 1-RM strength noted in the study by Padilha et al. (2015) may allude to the potential for larger strength gains from an increase in resistance training frequency.&#xA0;</li>
 <li>1x/week, 2x/week, or 3x/week: Increasing training frequency for older exercisers, especially when comparing 3x/week to 1-2/week, may result in a significant increase in strength improvement. However, it may be worth noting that larger improvements may not be attained for all movements or <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> groups.</li>
 <li>Rate of Recovery: Older exercisers are likely to exhibit a return to pre-exercise values (recovery time) 24 hours post-exercise for most strength, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, and functional tests; however, higher-intensity training (heavier loads) may increase recovery time. Further, certain neuromuscular attributes related to eccentric loading and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> may require 48 hours of recovery time.&#xA0;</li>
</ul>
<h3>1x/week versus 2x/week</h3>
Several studies have demonstrated that older exercisers may improve strength with resistance training just 1 - 2x/week. DiFrancisco-Donoghue et al. compared 18 novice exercisers (age: 65-79 years) randomly assigned to a 1x/week group or 2x/week group. Participants completed a full body program (leg press, knee extensions, leg curls, chest flies, arm curls, and seated dips) for 9 weeks, 1 set/exercise, 10-15 reps to failure/exercise, with 75% 1-RM loads. The results demonstrated that both groups exhibited significant and similar increases in leg press, knee extension, leg curl, chest fly, arm curl, and seated dip 1-RM strength (97). An RCT mentioned above by Walker et al. compared 38 novice female exercisers (age: 64-75 years) randomly assigned to a control group (no exercise), 1x/week group, or 2x/week group. All exercisers performed an introductory resistance training program for 12 weeks, 2x/week, followed by 24 weeks of the experimental assignment. The resistance training routine included a full body program (leg press, knee extensions, leg curls, chest press, lat pulldowns, shoulder press, seated rows, bicep curls, tricep pushdowns, abdominal curls, and back extensions). The 12-week introductory period included at least 1 set/exercise, 14-20 reps to failure/set, 50-60% 1-RM loads, short (1 min) rest between sets, and a moderate (2:0:2) rep tempo. The 24-week intervention period included 2-5 sets/exercise, 4-12 reps/set, 30-90% of 1-RM loads, and a moderate (1-3 min) rest between sets. Leg press 1-RM strength (and EMG activity during testing) increased during the introductory period, and continued to increase similarly during the experimental period for both groups (4). An RCT by Liu-Ambrose et al. compared 155 novice female exercisers (age: 65-75 years) randomly assigned to a control group (<a id="balance" data-tip="1190" target="_blank" href="/glossary-term/balance" class="glossary">balance</a> and <a id="tone" data-tip="1639" target="_blank" href="/glossary-term/tone" class="glossary">tone</a> group), 1x/week group, or 2x/week group. Exercisers completed a full body program (bicep curls, tricep extensions, seated rows, lat pulldowns, leg press, hamstring curls, calf raises, mini-squats, mini-lunges, and lunge walks) for 12 months, 2 sets/exercise, and 6-8 reps to failure/set. The <a id="balance" data-tip="1190" target="_blank" href="/glossary-term/balance" class="glossary">balance</a> and <a id="tone" data-tip="1639" target="_blank" href="/glossary-term/tone" class="glossary">tone</a> group completed stretching, abdominal strengthening, balancing exercises (crane and tree pose, tandem stance, tandem walk, and single-leg stance), and relaxation techniques. None of the groups exhibited changes in leg press 1-RM strength or gait speed, only the 2x/week group increased leg press <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> output, and the 1x/week group exhibited a decrease in leg press <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> output (98). These studies suggest that older exercisers may initially (9-12 weeks) exhibit a similar increase in strength from resistance training 1x/week or 2x/week; and after the initial period, 1x/week may be sufficient to maintain or increase strength. However, research also suggests that lower body <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> may require a minimum frequency of 2x/week.&#xA0;
<h3>2x/week versus 3x/week</h3>
In several studies mentioned above, strength was assessed following resistance training frequencies of 2x/week or 3x/week. da Silva et al. compared 30 experienced female exercisers who were not currently exercising (age: &#x2265; 60 years) and were randomly assigned to a 2x/week group, or a 3x/week group. Participants completed a full body program (chest press, leg press, rows, leg extensions, bicep curls, leg curls, lat pulldowns, and seated calf raises) for 24 weeks, 1-2 sets/exercise, 10-15 RM/set, moderate (1-2 min) rest between sets and exercises, and a 2:1 rep tempo ratio (eccentric to concentric). Results demonstrated similar increases in chest press, leg extension, and bicep curl 1-RM strength (99). Padilha et al. compared 27 novice female exercisers (age: 68.8 &#xB1; 4.8 years) randomly assigned to a 2x/week group or 3x/week group. Participants completed a full body program (chest press, leg press, rows, knee extensions, preacher curls, leg curls, tricep press downs, and seated calf raises) for 12 weeks, 1 set/exercise, 10-15 reps to failure/set, a moderate (2-3 min) rest between exercises, and a rep tempo ratio of 2:1 (eccentric to concentric). Note, participants completed 12 weeks of training, then 12 weeks of no training. Results demonstrated that the 3x/week group exhibited larger increases in chest press 1-RM strength, both groups exhibited similar increases in knee extension and preacher curl 1-RM strength, and groups exhibited similar decreases in chest press, knee extension, and preacher curl 1-RM strength following 12-weeks of detraining (6). Lastly, a pilot RCT by Norris et al. compared 30 novice male (age: 46-76 years) prostate cancer survivors randomly assigned to a 2x/week group or 3x/week group. Participants completed a full body program (chest press, leg press, lat pulldowns, leg curls, shoulder press, and leg extensions) for 12 weeks, 2 sets/exercise, 8-12 reps/exercise, 60-80% 1-RM loads, and a moderate (1-2 min) rest between sets. Results demonstrated similar improvements in strength (upper body and lower body strength) (100). These studies suggest that older exercisers may not see significant differences in strength when comparing 12 - 24 weeks of resistance training with a&#xA0; frequency of 2x/week or 3x/week, including similar rates of strength loss when followed by a detraining period. However, the increase in chest press 1-RM strength noted in the study by Padilha et al. (2015) may allude to the potential for larger strength gains from an increase in resistance training frequency.&#xA0;
<h3>1x/week, 2x/week, or 3x/week</h3>
Studies comparing resistance training frequencies of 1x/week to 3x/week suggest that frequency may have a significant effect on strength improvements for older exercisers. Campa et al. compared 45 novice female exercisers (age: 50 &#xB1; 8.7 years) randomly assigned to a 1x/week group or 3x/week group. Participants completed a full body program (leg extensions and leg press, lat machine and low rows, pectoral machine and chest press, and shoulder press) for 24 weeks, 4 sets/exercise, 8-12 reps/set, 60-80% 1-RM, short (1 min) rest between sets, and a moderate (2 min) rest between exercises. Results demonstrated that the 3x/week group exhibited larger improvements in strength, including dominant handgrip isometric strength, absolute handgrip isometric strength, and relative handgrip isometric strength (40). An RCT by Fernandez-Lezaun et al. compared 88 novice exercisers (age: 69 &#xB1; 3 years) randomly assigned to a control group (no exercise), or groups performing resistance training 1x/week, 2x/week, or 3x/week. Participants completed a 9-month intervention, including 3 months of an initial training period with a frequency of 2x/week and 6 months of the experimental protocol. The individual exercises were not reported, but are presumed to be part of a full-body routine, and acute variables progressed linearly, including 2-5 sets/exercise, 6-20 reps/ set, 30-90% 1-RM loads, and rest between sets between 0 rest - 4 min (no rest for super-sets). Results demonstrated that females in all 3 groups exhibited similar increases in leg press 1-RM strength; however, only the males in the 3x/week group exhibited an increase in leg press 1-RM strength (54). An RCT by Farinatti et al. compared 48 novice female exercisers (age: 60-78 years) who were randomly assigned to a control group (no exercise), or groups performing resistance training 1x/week, 2x/week, or 3x/week. Participants completed a full body program (squat with dumbbells, dumbbell bench press, seated dumbbell curls, knee extensions, standing calf raises, lat pulldowns, sit-ups, hip abductions, tricep press downs, and dumbbell military press) for 16 weeks, 1 set/exercise, 10-RM/set, a moderate (2-3 min) rest between exercises, and a moderate (2:0:2) rep tempo. Results demonstrated all groups exhibited similar improvements in dumbbell bench press and standing calf raise 10-RM strength. However, increased frequency resulted in larger increases in knee extension and dumbbell curl 10-RM strength (3x/week more than 2x/week more than 1x/week) (101). These studies demonstrate that increasing training frequency for older exercisers, especially when comparing 3x/week to 1-2x/week, may result in a significant increase in strength improvement. However, it may be worth noting that larger improvements may not be attained for all movements or <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> groups.
<h3>Rate of Recovery</h3>
Studies comparing strength and <a id="torque" data-tip="1294" target="_blank" href="/glossary-term/torque" class="glossary">torque</a> post-exercise may have implications for <a id="optimal" data-tip="1571" target="_blank" href="/glossary-term/optimal" class="glossary">optimal</a> rest time between resistance training sessions for older exercisers. Ferri et al. compared 9 physically active men (age: &gt; 65 years), 5 min, 24 hours, and 48 hours post-exercise. Participants completed calf raises, 10 sets/exercise, 10 reps/set, 70% 1-RM/set, a moderate (1.5 min) rest between sets, and a slow (3:0:3) rep tempo. Results demonstrated that compared to pre-exercise values, there was no significant post-exercise change in EMG activity (soleus, gastrocnemius, and tibialis <a id="anterior" data-tip="1566" target="_blank" href="/glossary-term/anterior" class="glossary">anterior</a>), plantar flexion M-wave amplitude, or maximal voluntary activation. Plantar flexion evoked twitch amplitude, contract time, and half relaxation time decreased significantly immediately post-exercise, but returned to pre-exercise values 24 hours post-exercise. Plantar flexion post-exercise maximal <a id="torque" data-tip="1294" target="_blank" href="/glossary-term/torque" class="glossary">torque</a> did not significantly change for 0&#xB0;/sec or 60&#xB0;/sec rep tempos; however, 5-min post-exercise plantar flexion maximal <a id="torque" data-tip="1294" target="_blank" href="/glossary-term/torque" class="glossary">torque</a> decreased by 8.8% for -60&#xB0;/sec (eccentric <a id="torque" data-tip="1294" target="_blank" href="/glossary-term/torque" class="glossary">torque</a>) and 15.7% at 120&#xB0;/sec, and both returned to pre-exercise values at 24 hours post-exercise (102). Orssato et al. compared 15 male and 7 female novice exercisers (age: &#x2265; 60 years) immediately, 24 hours, 48 hours, and 72 hours post-exercise. Note, participants were randomly assigned to either 70% or 95% of 5-RM load. All participants completed leg press and leg curls, 3 sets/exercise, reps to failure/set, moderate (2 min) rest between sets and exercises, and a moderate (2:0:1) rep tempo. Both groups exhibited a decrease in performance immediately post-exercise for the countermovement jump (CMJ), timed up-and-go <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>, and stair ascent <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>, and a return to pre-exericse values 24 hours post-exercise. Both groups also exhibited reductions in the rate of <a id="torque" data-tip="1294" target="_blank" href="/glossary-term/torque" class="glossary">torque</a> development (from 0-50ms) immediately post-exercise, and a return to pre-exercise values 24 hours post-exercise; however, the rate of <a id="torque" data-tip="1294" target="_blank" href="/glossary-term/torque" class="glossary">torque</a> development (from 0-200ms) did not return to baseline until 48 hours post-exercise. The findings demonstrated a significant difference between groups, with the 70% 5-RM load group exhibiting a significant decrease in knee extension peak <a id="torque" data-tip="1294" target="_blank" href="/glossary-term/torque" class="glossary">torque</a> immediately post-exercise, and a return to pre-exercise values 24 hours post-exercise. And, the 95% 5-RM load group exhibited a significant decrease in knee extension peak <a id="torque" data-tip="1294" target="_blank" href="/glossary-term/torque" class="glossary">torque</a> both immediately and 24 hours post-exercise, and a return to pre-exercise values 48 hours post-exercise (103). In summary, these studies suggest that older exercisers are likely to exhibit a return to pre-exercise values (recovery time) 24 hours post-exercise for most strength, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, and functional tests; however, higher-intensity training (heavier loads) may increase recovery time. Further, certain neuromuscular attributes related to eccentric loading and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> may require 48 hours of recovery time.&#xA0;
<img alt="Med ball slams for abdominal training" title="A client demonstrating an explosive core exercise" src="https://www.datocms-assets.com/25800/1644873922-core-power.png">

Frequency: Strength, Power, and Older Exercisers

Frequency: Strength, Power, and Young Exercisers

<h3>Summary</h3>
<ul>
 <li>Reps to Failure versus Reps in Reserve: <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Resistance training with a reps-in-reserve/set protocol is likely to result in a decrease in strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> for a relatively short duration (6 hours or less). A <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">reps-to-failure/set protocol will likely result in a larger decrease in strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> for a significantly longer duration (2 days or more).</li>
 <li><span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">When Volume is Similar: When exercise volume is similar and sufficient, performing reps to failure/set still has a significantly larger influence on post-exercise reductions in strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>. When compared to pre-exercise values, strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> may be reduced for just 6 hours following a reps-in-reserve/set protocol, whereas the same routine performed with reps-to-failure/set may require 3 days of recovery time.</li>
 <li><span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Addition of Load or Velocity: When the number of reps/set during a reps-in-reserve/set protocol is matched by increasing the load until reps-to-failure/set is reached, the increase in load significantly increases the amount of time that a decrease in strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> is exhibited (2 - 3 days). Surprisingly, increasing velocity during reps-in-reserve/set protocols did not result in larger decreases in performance or increases in recovery time.&#xA0;</li>
</ul>
<h3>Reps-to-Failure versus Reps-in-Reserve</h3>
Studies have demonstrated that performing repetition to failure may significantly influence recovery time. Gonz&#xE1;lez-Badillo et al. compared 9 experienced male exercisers (age: 23.3 &#xB1; 3.9 years) 5 min, 6 hours, 1 day, and 2 days post-exercise, following a reps-to-failure/set protocol or a half-reps/set protocol, performed in random order 14 days apart. Participants completed bench press and squats, 3 sets/exercise, 4 or 8 reps/set, 8-RM loads, with long (10 min) rest between exercises. The findings demonstrated that only the reps-to-failure/set protocol resulted in a decrease in average bench press barbell velocity 5 min post-exercise, but velocities returned to pre-exercise values 6 hours post-exercise. Squat mean barbell velocity decreased significantly for both protocols 5 min post-exercise, the half-reps/set protocol returned to pre-exercise values 6 hours post-exercise, and the reps to failure/set group did not return to pre-exercise values until re-assessment 48-hours post-exercise. Additionally, counter-movement jump height was significantly reduced for the reps-to-failure/set group during reassessment at 5 min, 6 hours, and 1 day post-exercise, and did not return to pre-exercise values within the 2-day testing period. The half-reps/set group only exhibited a significant decrease in counter-movement jump height 5 min post-exercise (11). Pareja-Blanco et al. compared 10 novice male exercisers (age: 20.6 &#xB1; 2.7 years) immediately, 6 hours, 1 day, and 2 days post-exercise after completing 3 different protocols separated by 2 weeks (and following a resistance training program). Protocol 1 (reps to failure protocol) included reps to failure/set with a 10-RM load; protocol 2 (half reps protocol) included 5 reps/set with a 10-RM load; protocol 3 (half reps after training protocol) included 5 reps/set with a 10-RM load after completing a 10-week resistance training program. All protocols included bench presses and squats, 3 sets/exercise, long (5 min) rest between sets, and long (10 min) rest between exercises. The 10-week resistance training program included the same protocol for 10 weeks (18 sessions). <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">The findings demonstrated that the reps to failure protocol resulted in the largest decrease in bench press velocity immediately, 6 hours, and 24 hours post-exercise, and return to pre-exercise values 48 hours post-exercise. The half reps protocol (prior to training) resulted in a decrease in velocity immediately following exercise and a return to pre-exercise values 6 hours post-exercise, and 10 weeks of training followed by the half-reps protocol resulted in a smaller decrease in velocity and a return to pre-exercise values 6 hours post-exercise. All groups exhibited a significant decrease in squat velocity immediately post-exercise, however, the reps to failure protocol resulted in the largest decrease in velocity, followed by the half rep protocol, and the smallest decrease was exhibited by the half reps following training protocol. All protocols resulted in near pre-exercise values 6 hours after exercise (10). <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">These studies suggest that resistance training with a reps-in-reserve/set protocol is likely to result in a decrease in strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> for a relatively short duration (6 hours or less). A <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">reps-to-failure/set protocol will likely result in a larger decrease in strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> for a significantly longer duration (2 days or more).
<span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;"><img alt="Female personal trainer coaching a client doing pushups with feet in straps" src="https://www.datocms-assets.com/25800/1662302904-lawrence-wilcox-mcp9atidcak-unsplash.jpg" title="A client performing pushups with feet in straps">
<h3><span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">When Volume is Similar </h3>
<span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Additional studies suggest that volume may not be the most influential variable comparing outcomes following protocols with rep-to-failure/set or reps-in-reserve/set. <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Mangine et al. compared 14 experienced male exercisers (age: 24.6 &#xB1; 3.0 years) 6 hours, 1 day, 2 days, and 3 days post-exercise. All participants performed the bench press, 5 sets/session, 80% of 1-RM loads, long (3-4 min) rest between sets, with 2 different reps/set protocols, on different days in randomized order. The &quot;reps in reserve&quot; protocol included 4 sets/session with a self-determined 3 reps-in-reserve for sets 1-4, and reps-to-failure for set 5. The reps-to-failure protocol included all 5 sets performed with reps-to-failure/set. These protocols resulted in a similar number of total reps and work performed for each session; however, barbell velocity and rate of perceived exertion were better maintained by the reps-in-reserve protocol. The findings demonstrated that neither group exhibited a significant decrease in mean barbell velocity or impulse during re-assessment 1 day, 2 days, or 3 days post-exercise (27). <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Mor&#xE1;n-Navarro et al. compared 10 experienced male exercisers (age: 21.5 &#xB1; 4.0 years) immediately, 6 hours, 1 day, 2 days, and 3 days post-exercise. Participants completed 3 different exercise protocols separated by 4 weeks in randomized order: the low-volume protocol included 3 sets/exercise, 5 reps/set, without reaching failure; the high-volume protocol included 6 sets/exercise, 5 reps/set, without reaching failure; and the low-volume to failure protocol included 3 sets/exercise, 10 reps/set, with reps to failure/set. All exercise protocols included Smith machine bench press and squats, with 75% of 1-RM loads, and long (5 min) rest between sets. The findings demonstrated that only the low-volume to-failure group exhibited a significant decrease in bench press and squat mean propulsive velocity during re-assessment immediately, 1 day, 2 days, or 3 days post-exercise (for both moderate and heavy loads). All groups exhibited a significant decrease in countermovement jump height immediately post-exercise; however, the groups not performing reps to failure/set returned to pre-exercise values 6 hours post-exercise. The low-volume to failure group exhibited a larger decrease in jump height during all re-assessment periods and did not return to pre-exercise values until day 3 (12). Last, Ramos-Campo et al. compared 15 experienced male exercisers (age: 23.4 &#xB1; 2.4 years) 1 day after 2 different volume-equated protocols, performed in randomized order at least 1 week apart. The reps-to-failure protocol included 4 sets/exercise, 10 reps to failure/set, with approximately 75% of 1-RM, and the reps-in-reserve protocol included 5 sets/exercise, 8 reps/set, and approximately 75% of 1-RM loads. Both protocols included bench press and squats, with moderate (1.5 min) rest between sets. Both protocols resulted in similar sleep quality and heart rate variability post-exercise (pre-exercise values were not measured), and only the reps-to-failure protocol exhibited a significant decrease in bench press and squat 1-RM strength 1-day post-exercise (111). <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">These studies suggest that when exercise volume is similar and sufficient, performing reps to failure/set still has a significantly larger influence on post-exercise reductions in strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>. When compared to pre-exercise values, strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> may be reduced for just 6 hours following a reps-in-reserve/set protocol, whereas the same routine performed with reps-to-failure/set may require 3 days of recovery time.
<h3><span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Addition of Load or Velocity</h3>
Two additional studies imply that load contributes to the effects reps to failure/set may have on recovery rates. Amdi et al. compared 31 experienced exercisers (15 females age: 26 &#xB1; 4 years, 16 males age: 28 &#xB1; 4 years) 5 min, 1 day, 2 days, and 3 days post-exercise following random assignment to 5 reps/set with 80% of 1-RM load group (approximately half-reps to failure/set), or reps to failure/set with 4-6 RM loads. All participants performed squats, for 5 sets/exercise, with long (&#x2265; 5 min) rest between sets. The findings demonstrated that the 5 reps/set of 80% of 1-RM protocol resulted in a significant decrease in average concentric velocity when compared to pre-exercise values. Men exhibited a decrease 5 min and 1 day post-exercise, and then exceeded pre-exercise values 2 days post-exercise. Women exhibited a decrease 5 min post-exercise and then exceeded pre-exercise values 1 day post-exercise. The reps-to-failure/set with 4-6 RM loads protocol resulted in significantly larger decreases in leg press average concentric velocity. Men and women did not exhibit near pre-exercise values until 2 days post-exercise and still exhibited a trend toward lower values 3 days post-exercise (112). Linnamo et al. compared 8 novice men and 8 novice women (age: 27.1 &#xB1; 0.7 years) immediately, 1 hour, and 2 hours post-exercise, following 3 different protocols each separated by 2 weeks. The protocols included ~10 reps-to-failure/set with 70% of 1-RM loads and a self-selected tempo, 10 reps/set with 40% of 1-RM load and a self-selected tempo, and 10 reps with 40% of 1-RM loads with a max velocity tempo. All participants completed 3 exercises (bench press, sit-ups, and leg press), for 5 sets/exercise, 10 reps/set, with moderate (2 min) rest between sets. The findings demonstrated that all interventions resulted in a significant decrease in leg press maximal force immediately, 1 hour, and 2 hours post-exercise. The 10 reps to failure/set protocol resulted in the largest decreases, followed by the 10 reps/set with 40% of 1-RM load and self-selected tempo protocol, and the 10 reps with 40% of 1-RM loads with a max velocity tempo protocol resulted in the smallest decreases in force (9). These studies suggest that when the number of reps/set during a reps-in-reserve/set protocol is matched by increasing the load until reps-to-failure/set is reached, the increase in load significantly increases the amount of time that a decrease in strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> is exhibited (2 - 3 days). Surprisingly, increasing velocity during reps-in-reserve/set protocols did not result in larger decreases in performance or increases in recovery time.&#xA0;
<ul></ul>

Recovery Time: Strength, Power, and Reps-to-Failure/Set

Recovery Time: Strength, DOMS, and Exercise Type

Recovery Time: Strength, Power, DOMS, and Acute Variables

<h3>Summary</h3>
<ul>
 <li>Age: Either younger or older exercisers may exhibit larger post-exercise reductions in strength, increases in DOMS, and recovery time; however, both age groups are likely to exhibit similar improvements following a 2nd session. &#xA0;&#xA0;</li>
 <li>Exercise Type: Various exercise types may result in similar changes in strength, DOMs, and rates of recovery following a 1st session and similar improvements in recovery time following a 2nd session. However, changes in strength, DOMS, and rates of recovery may be larger following upper-body exercise when compared to lower-body exercise, and larger following eccentric contractions when compared to concentric contractions. Note, larger post-exercise changes following a 1st session often result in larger improvements following a 2nd session. &#xA0;</li>
 <li>Higher Frequencies: The decrease in strength, increase in DOMS, and recovery following the 1st session, will improve significantly following a 2nd session, and additional reductions may occur in subsequent sessions. Further, the study by Bartolomei et al. (2022) suggests that these changes in strength and soreness may be reduced by dividing a single higher-volume resistance training session into 2 lower-volume sessions.</li>
 <li>Strange Finding, Adaptations Across Limbs: <a id="unilateral" data-tip="1551" target="_blank" href="/glossary-term/unilateral" class="glossary">unilateral</a> resistance training results in some adaptations by both limbs and/or systematic changes that significantly reduce post-exercise reductions in performance and improve recovery times.&#xA0;</li>
</ul>
<h3>Age:</h3>
Two studies mentioned in the previous section compared DOMS and the recovery rate of younger and older adults, following repeated sessions. Chen et al. compared 39 novice male exercisers (pre-adolescents age: 9.4 &#xB1; 0.5 years, adolescents age: 14.3 &#xB1; 0.4 years, adults age: 22.6 &#xB1; 2.0 years) immediately and 1 time a day for 5 days post-exercise. Participants completed eccentric elbow flexion during two exercise sessions separated by 3 weeks. Adult exercisers exhibited significantly larger decreases in strength, increases in DOMS, and slower recovery rates than pre-adolescent or adolescent exercisers; however, all exercisers exhibited significant improvements following the 2nd session (17). Also mentioned above, Lavender et al. compared 20 novice male exercisers (young age 20.4 &#xB1; 2.0 years; elderly age: 70.5 &#xB1; 4.1 years) immediately, 1 hour, 1 day, 2 days, 3 days, and 4 days post-exercise. Participants completed eccentric bicep curls during two exercise sessions separated by 4 weeks. Compared to older exercisers, young exercisers exhibited larger decreases in MVIC following both the 1st and 2nd sessions. Additionally, following the first session young exercisers exhibited significantly more DOMS and failed to return to pre-exercise values by day 4, whereas elderly exercisers exhibited less soreness and had returned to near pre-exercise values by day 4. Following the second session both groups exhibited similar and significantly less soreness, and both groups returned to near pre-exercise values 3 - 4 days post-exercise (25). Last, Heckel et al. compared 10 young and 10 elderly physically active men (young age: 25. 1 &#xB1; 4.9 years; older age: 64.5 &#xB1; 5.5 years) 1 day, 2 days, 7 days, and 15 days post-exercise. This study required participants to complete 6 sessions throughout a 15-day period, with sessions completed on day 1, day 3, day 5, day 8, day 10, and day 12. Participants completed right leg knee extensions via an isokinetic dynamometer, 4 sets/session, 15 reps/set, short (1 sec) rest between reps, moderate (2 min) rest between sets, and a moderate (60&#xB0;/sec) rep tempo. Testing was completed on day 1, day 2, day 3, day 8, and day 15. The findings demonstrated that only the young men exhibited a significant decrease in the rate of force development and only following the 1st session. Older men exhibited larger increases in DOMs; however, both groups exhibited peak soreness on the 7th day of the protocol and a return to 1st session values by day 15 (22). These studies imply that either younger or older exercisers may exhibit larger post-exercise reductions in strength, increases in DOMS, and increases in recovery time, suggesting that other variables may have a stronger correlation with post-exercise changes. Note, both age groups are likely to exhibit similar reductions in strength loss post-exercise, and recovery time following a 2nd session. &#xA0; &#xA0;
<h3>Exercise Type</h3>
Additional studies compare DOMS and recovery rates following repeated sessions of various exercise types. <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Hortob&#xE1;gyi et al. compared 9 male and 9 female novice exercisers (age: 22.6 &#xB1; 2.7 years) 2 days, 4 days, and 7 days post-exercise. Participants were randomly assigned to an exercise or control (no exercise) group, and the exercise group completed 2 sessions separated by 2 weeks. The exercise protocol included eccentric knee extensions, 10 sets/exercise, 10 reps/set, 80% of 1-RM loads, and long (3 min) rest between sets. The findings demonstrated that following the first session, exercisers exhibited significant decreases in dynamic, isokinetic, and isometric strength, and increases in DOMS, with peak changes noted 2-days post-exercise, dynamic strength returning to near pre-exercise values 4 days post-exercise, and isokinetic strength, isometric strength, and DOMS remaining slightly but significantly different from pre-exercise values 7 days post-exercise (last day of re-assessment). <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Following the second session, changes in strength and DOMS failed to reach statistical significance (74). Coratella et al. compared 13 active males (age: 21.7 &#xB1; 3.1 years) immediately, 1 day, 2 days, 3 days, and 4 days post-exercise. Participants completed squats on a flywheel ergometer, 10 sets/exercise, 10 reps/set, and short (1 min) rest between sets, during 2 exercise sessions separated by 2 weeks. Results demonstrated that following the first session, MVIC decreased significantly, with the largest decrease exhibited immediately post-exercise, a gradual increase in MVIC during subsequent reassessments, and a return to near pre-exercise values on day 4. Following the 2nd session, MVIC decreased less and returned to pre-exercise values 2 days post-exercise. DOMS increased significantly following the first session, peaked 1 - 2 days post-exercise, and improved but did not return to pre-exercise values on days 3 and 4. Following the second session DOMS increased less, peaked on day 2, and was near pre-exercise values on day 3 (36). Saka et al. compared 12 novice male exercisers (age: 25 &#xB1; 3 years) immediately, 1 day, 2 days, 3 days, and 7 days post-exercise. Participants completed eccentric bicep curls and eccentric knee extensions in separate sessions 2 weeks apart, 3 sets/exercise, 15 reps/set, and short (1 min) rest between sets, with a slow (30&#xB0;/sec) rep tempo. The findings demonstrated that eccentric biceps curls resulted in a significant decrease in peak <a id="torque" data-tip="1294" target="_blank" href="/glossary-term/torque" class="glossary">torque</a>, with the largest decrease exhibited immediately following exercise, gradual improvement during each subsequent reassessment, and a return to near pre-exercise values 7 days post-exercise. Eccentric knee extensions did not result in a significant decrease in peak <a id="torque" data-tip="1294" target="_blank" href="/glossary-term/torque" class="glossary">torque</a> during any reassessment period. Results demonstrated that DOMS increased significantly following eccentric bicep curls, peak soreness was exhibited 2-3 days post-exercise, and had returned to near pre-exercise values by 7 days post-exercise. Eccentric knee extensions resulted in smaller increases in soreness, peak soreness was exhibited 1-2 days post-exercise, and had returned to near pre-exercise values 7 days post-exercise (29). Last, Bamman et al. compared 10 novice male and female exercisers (age: 24.4 &#xB1; 0.7 years) 0.5 hours, 1 hour, 2 hours, 4 hours, 8 hours, 1 day, and 2 days post-exercise. Participants completed two squat sessions separated by 6-10 days. Each squat session entailed concentric-only or eccentric-only reps, 8 sets/exercise, 8 reps/set, 85% 1-RM for concentric squats, and 110% 1-RM for eccentric squats. The findings demonstrated that only the eccentric squat protocol resulted in a significant decrease in knee extension MVIC, elevated serum concentrations of creatine kinase, and increased DOMS, with the largest changes exhibited during reassessment on day 2 (16). These studies suggest that various exercise types may result in similar changes in strength, DOMs, and rates of recovery following a 1st session and similar improvements in recovery time following a 2nd session. However, changes in strength, DOMS, and rates of recovery may be larger following upper-body exercise when compared to lower-body exercise, and larger following eccentric contractions when compared to concentric contractions. Note, larger post-exercise changes following a 1st session often result in larger improvements following a 2nd session.&#xA0;&#xA0;
<h3>Higher Frequencies:</h3>
Additional studies have compared increases in DOMS and the rate of recovery following multiple sessions (more than 2). As mentioned several times above, Heckel et al. compared 10 young and 10 elderly physically active men (young age: 25. 1 &#xB1; 4.9 years; older age: 64.5 &#xB1; 5.5 years) 1 day, 2 days, 7 days, and 15 days post-exercise. This study required participants to complete 6 sessions throughout a 15-day period, with sessions completed on day 1, day 3, day 5, day 8, day 10, and day 12. The findings demonstrated that only the young men exhibited a significant decrease in the rate of force development and only following the 1st session. Older men exhibited larger increases in DOMs; however, both groups exhibited peak soreness on the 7th day of the protocol and a return to 1st session values by day 15 (22). Bartolomei et al. compared 24 experienced male exercisers (age: 24.4 &#xB1; 1.6 years) 15 min, 1 day, and 2 days post-exercise, following random assignment to 1 or 2 sessions per day (4 hours of rest between sessions). Participants completed bench press for 10 reps/set, with 70% of 1-RM, moderate (1.25 min) rest between sets, the 1 session group completed 8 sets/session, and the 2 session group completed 4 sets/session. The results demonstrated that both groups exhibited similar decreases in bench press throw <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> immediately following exercise; however, the 1 session group returned to near pre-exercise values on day 2, and the 2 session group returned to near pre-exercise values on day 1. Neither group exhibited a decrease in bench press MVIC following the bench press protocols; however, both groups exhibited similar increases in pectoralis major soreness, with peak values exhibited 1-day post-exercise and a return to near pre-exercise values 2 days post-exercise (121). Chen et al. compared 15 novice male exercisers (age: 21.8 &#xB1; 1.9 years) immediately, 3 hours, 1 day, 2 days, 3 days, 4 days, and 5 days post-exercise. The exercise protocol was repeated 4 times, with 4 weeks between sessions, over a 16-week period. Participants completed eccentric elbow flexion via an isokinetic dynamometer, 4 sets/exercise, 30 reps/set, short (10 sec) rest between reps, and a fast (1-sec) rep tempo. The findings demonstrated that strength (MVIC and MVCC) decreased immediately following all sessions; however, the loss of strength occurred more at 50&#xB0; and 70&#xB0;, than at 90&#xB0;, 110&#xB0;, 140&#xB0;, and 160&#xB0; of elbow flexion. Following the first session, the largest decrease in strength was exhibited immediately post-exercise, with gradual recovery during each reassessment, but pre-exercise values were not reached by day 5. After the 2nd session, there was a smaller decrease in strength immediately post-exercise, and a return to near pre-exercise values on day 5. And, following the 3rd and 4th sessions immediate reductions in strength were similar; however, following the 3rd session pre-exercise values were exhibited on day 4, and following the 4th session pre-exercise values were exhibited on day 2. Following all sessions, delayed onset <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> soreness increased significantly. Session 1 resulted in the largest increases in DOMS, peaking on days 1 and 2, improving on days 3 -5, but failing to reach pre-exercise values. Following the 2nd session, DOMS was less, peaked on days 1 and 2, improved on days 3 and 4, and returned to pre-exercise values on day 5. Following the 3rd and 4th sessions, DOMS was similar, peaking 1 day after exercise, improving on days 2 and 3, and returning to near pre-exercise values on day 4 (38). These studies suggest that the decrease in MVIC, increase in DOMS, and recovery time following the 1st session, will improve significantly following a 2nd session, and additional reductions may occur in subsequent sessions. Further, the study by Bartolomei et al. (2022) suggests that these changes in strength and soreness may be reduced by dividing a single higher-volume resistance training session into 2 lower-volume sessions.
<h3>Strange Finding: Adaptations Across Limbs:&#xA0;</h3>
A study by Hody et al. compared 18 novice male exercisers (age: 22.9 &#xB1;1.8 years) 1 day post-exercise following single-leg eccentric knee extensions on an isokinetic dynamometer with dominant and non-dominant legs, in random order, during separate sessions performed 6 weeks apart. Participants completed 3 sets/session, 30 reps/set, short (0.5 min) rest between sets, and a moderate (60&#xB0;/sec) rep tempo. The findings demonstrated that 1 day post-exercise, dominant and non-dominant knee extensions resulted in similar decreases in MVIC, <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> stiffness, and DOMS. However, despite using the other leg in the 2nd session, a significant reduction in the change in post-exercise outcomes measures was noted (39). This may imply that <a id="unilateral" data-tip="1551" target="_blank" href="/glossary-term/unilateral" class="glossary">unilateral</a> resistance training results in some adaptations by both limbs, and/or systematic changes that significantly reduce post-exercise reductions in performance and improve recovery times.&#xA0;

Recovery Time: Strength, DOMS and Repeated Sessions

Recovery Time: Strength, Power, Gender, and Age

<h3>Summary&#xA0;</h3>
<ul>
 <li>Gender: The findings of the available research are not congruent, suggesting that men or women could experience higher peak DOMS and/or longer recovery times (return to near pre-exercise values). This likely implies variables other than gender have a more significant influence on recovery (e.g. relative strength, relative effort, familiarity with the exercises performed in the study, etc.). Further, these studies may imply a correlation between the number of days experiencing DOMS, and the number of days exhibiting a decrease in strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>. &#xA0;</li>
</ul>
Age
<ul>
 <li>Young Adults Compared to Middle-aged Adults: Young adults and middle-aged adults are likely to exhibit similar decreases in performance, increases in DOMS, and similar recovery rates. However, some studies show middle-aged individuals exhibit slightly slower recovery rates, and one study demonstrated that young adults exhibited higher peak soreness. Further, the study by Gordon et al. (2017) demonstrated that a post-exercise loss in strength may occur without a significant increase in DOMS.</li>
 <li>Young Adults Compared to Older Adults: Older adults are likely to experience higher peak DOMS, and potentially a slower recovery rate when compared to young adults; however, this is not always the case. Further, young adults and older adults exhibit similar reductions (improvements) in DOMS and an increase in recovery rate with repeated sessions.</li>
 <li>Adolescents Compared to Young Adults: In summary, adult exercisers exhibited significantly larger decreases in strength, increases in DOMS, and slower recovery rates than pre-adolescent or adolescent exercisers; however, all exercisers exhibited significant improvements following the 2nd session.</li>
</ul>
<h3>Gender</h3>
Several studies have investigated the effect of gender on recovery from delayed onset <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> soreness (DOMS). Davies et al. compared 19 experienced exercisers (11 males age: 23 &#xB1; 3 years, 9 females age: 24 &#xB1; 4 years) 4 hours, 1 day, 2 days, and 3 days post-exercise. Participants completed squats for 5 sets, 5 reps/set, 80% 1-RM loads, moderate (1.5 min) rest between sets, with a slow (6-sec/rep) rep tempo. Participants then completed squats for a 6th set, with 80% of 1-RM loads, and reps to failure. The findings demonstrated a significant decrease in strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, with peak decreases exhibited immediately post-exercise, strength returned 24 - 72 hours post-exercise, but <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> failed to return to pre-exercise values within the 72-hour <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a> period. Women exhibited significantly larger changes in strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> than men. Further, delayed onset <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> soreness (DOMS) increased significantly post-exercise, women reported significantly more pain (although the differences were relatively small), pain peaked 24 - 48 hours post-exercise, and improved, but did not return to pre-exercise values during re-assessment 72 hours post-exercise (26). Flores et al. compared 16 novice male and 14 novice female exercisers (males age: 22.69 &#xB1; 0.49 years, females age: 22.21 &#xB1; 0.71 years) immediately, 1 day, 2 days, 3 days, and 4 days post-exercise. Participants completed Scott curls, 8 sets/exercise, 10 reps/set, reps to failure/set, moderate (2 min) rest between sets, with a moderate (2-3:0:1) rep tempo. The findings demonstrated that men and women exhibited a similar initial decrease in strength immediately following the intervention, the largest recovery exhibited in the first 24 hours, a significant improvement between 24 and 48 hours, followed by a reduction in the rate of recovery that resulted in a small but significant decrease in strength still exhibited on the 4th day of testing. Women, in particular, exhibited little improvement in strength between days 2 - 4, and less total recovery. Men and women exhibited significant and similar increases in DOMS that peaked on day 2 and were still higher than pre-exercise values on day 4 (128). Dannecker et al. compared 33 recreationally active (weight lifted inconsistently) male and female exercisers (age: 23 &#xB1; 2.82 years) 1-hour, 1 day, 2 days, 3 days, and 4 days post-exercise. Participants completed eccentric bicep curls via an isokinetic dynamometer, 3 sets/exercise, 12 reps/set, short (1 min) rest between sets, and a fast (90&#xB0;/sec) rep tempo. Note, female exercisers participated during the follicular phase of their menstrual cycle. The findings demonstrated that all participants exhibited a post-exercise increase in pain and unpleasantness at rest, during dynamic contraction, and during isometric contraction. Peak values were exhibited 2 days post-exercise and gradually decreased on days 3 and 4 of testing. Men exhibited slightly more pain and unpleasantness and values were still significantly higher than pre-exercise values on the final day of testing (day 4); whereas, women exhibited slightly less pain and unpleasantness and had returned to near pre-exercise values on the final day of testing (134). The findings of these studies are not congruent, suggesting that men or women could experience higher peak DOMS and/or longer recovery times (return to near pre-exercise values). This likely implies variables other than gender have a more significant influence on recovery (e.g. relative strength, relative effort, familiarity with the exercises performed in the study, etc.). Further, these studies may imply a correlation between the number of days experiencing DOMS, and the number of days exhibiting a decrease in strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>.
<h3>Age</h3>
Young Adults Compared to Middle-aged Adults
Several studies have investigated the effects of age on DOMS and the rate of recovery. Arroyo et al. compared 9 young (age: 21.8 &#xB1; 2.2 years) and 10 middle-aged (age: 47.0 &#xB1; 4.4 years) recreationally active exercisers immediately, 0.5 hours, 1 hour, 2 hours, 1 day, and 2 days post-exercise. Participants completed knee extensions and curls on an isokinetic dynamometer, for 8 sets/exercise, 10 reps/set, short (1 min) rest between sets, with a moderate (60&#xB0;/sec) rep tempo. Results demonstrated no significant difference between groups for soreness or strength, although middle-aged exercisers exhibited larger decreases in <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> (19). Fernandes et al. compared 27 male participants, divided into 9 young experienced exercisers (age: 21-25 years), 9 middle-aged experienced exercisers (age: 35-54 years), and 9 middle-aged novice exercisers (age: 35-53 years). Participants completed squats, 10 sets/exercise, 10 reps/set with 60% 1-RM, reps to failure/later sets, and moderate (2 min) rest between sets. The findings demonstrated that 24 hours post-exercise all groups exhibited significant and similar decreases in squat peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> at 80% and 20% of 1-RM loads, and knee extension MVIC. 72 hours post-exercise small decreases were still present. DOMS followed a similar trend; however, middle-aged novice exercisers exhibited significantly more soreness 24 hours and 72 hours post-exercise (18). Gordon et al. compared 19 experienced male exercisers (age: 21.8 &#xB1; 2.0 and 47.0 &#xB1; 4.4 years) immediately, 0.5 hours, 2 hours, 1 day, and 2 days post-exercise. Participants completed concentric knee extension and eccentric knee flexion via an isokinetic dynamometer, 8 sets/exercise, 10 reps/set, short (1 min) rest between sets, and a moderate (60&#xB0;/sec) rep tempo. The findings demonstrated that both young and middle-aged exercisers exhibited similar decreases in peak <a id="torque" data-tip="1294" target="_blank" href="/glossary-term/torque" class="glossary">torque</a> (at 60&#xB0;/sec and 240&#xB0;/sec), average <a id="torque" data-tip="1294" target="_blank" href="/glossary-term/torque" class="glossary">torque</a> ( at 60&#xB0;/sec and 240&#xB0;/sec), and rate of <a id="torque" data-tip="1294" target="_blank" href="/glossary-term/torque" class="glossary">torque</a> development, with the largest decreases, exhibited immediately following exercise and a return to near pre-exercise values on the 2nd day. Neither group exhibited significant increases in DOMS; however, the middle-aged group exhibited an increase in circumference immediately post-exercise (20). Last, Lavender et al. compared 24 novice male exercisers (young adults age: 19 &#xB1; 0.4 years, middle age adults age: 48.0 &#xB1; 2.1 years) immediately, 1 day, 2 days, 3 days, and 4 days post-exercise. Participants completed eccentric Scott curls, 6 sets/exercise, 5 reps/set, short (3 sec) rest between reps, a slow (5 sec) rep tempo, and moderate (2 min) rest between sets. The findings demonstrated that young and middle-aged exercisers exhibited similar decreases in MVIC, with the largest decreases exhibited immediately post-exercise, some recovery exhibited with each subsequent <a id="assessment" data-tip="1478" target="_blank" href="/glossary-term/assessment" class="glossary">assessment</a>, but a failure to reach pre-exercise values by the 4th day. Additionally, young exercisers exhibited significantly larger increases in post-exercise pain during palpation and elbow extension, with peak soreness on day 3, and a small decrease in pain exhibited on day 4, whereas middle-aged exercisers exhibited less pain during palpation and elbow extension, with peak soreness on day 2 and significantly more recovery by day 4 (despite failing to reach pre-exercise values) (21). These studies suggest that young adults and middle age adults are likely to exhibit similar decreases in performance, increases in DOMS, and similar recovery rates. However, some studies show middle-aged individuals exhibit slightly slower recovery rates, and one study demonstrated that young adults exhibited higher peak soreness. Further, the study by Gordon et al. (2017) demonstrated that a post-exercise loss in strength may occur without a significant increase in DOMS.&#xA0;
Young Adults Compared to Older Adults
Additional studies have compared increases in DOMS and the rate of recovery of young adults and older adults post-exercise. Heckel et al. compared 10 young and 10 elderly physically active men (age: 25. 1 &#xB1; 4.9 years and 64.5 &#xB1; 5.5 years) 1 day, 2 days, 7 days, and 15 days post-exercise. This study required participants to complete 6 sessions throughout a 15-day period, with sessions completed on day 1, day 3, day 5, day 8, day 10, and day 12. Participants completed right leg knee extensions via an isokinetic dynamometer, 4 sets/session, 15 reps/set, short (1 sec) rest between reps, moderate (2 min) rest between sets, and a moderate (60&#xB0;/sec) rep tempo. Testing was completed on day 1, day 2, day 3, day 8, and day 15. The findings demonstrated that only the young men exhibited a significant decrease in the rate of force development and only following the 1st session. Older men exhibited larger increases in DOMs; however, both groups exhibited peak soreness on the 7th day of the protocol and a return to 1st session values by day 15 (22). Lavender et al. compared 20 novice male exercisers (young: 19.4 &#xB1; 0.4 years, older adult: 70.5 &#xB1; 1.5 years) immediately, 1 hour, 1 day, 2 days, 3 days, 4 days, 5 days, 7 days, and 10 days post-exercise. Participants completed eccentric bicep curls, 6 sets/exercise, 5 reps/set, 40% MVC load, short (3 sec) rest between reps, moderate (2 min) rest between sets, and a moderate (5 sec) rep tempo. The findings demonstrated that both groups exhibited a significant decrease in MVIC following exercise, with the largest decreases exhibited immediately post-exercise, MVIC improving gradually with each subsequent day, by day 10 the older adult exercisers had returned to near pre-exercise values but the young adults still exhibited a small but significant decrease in MVIC. Additionally, following the first session, both groups exhibited a significant increase in DOMS, with peak soreness exhibited 1 or 2 days post-exercise, and a gradual decrease in soreness exhibited on days 3 and 4. Young exercisers exhibited significantly more soreness and returned to pre-exercise values on day 7. Elderly exercisers exhibited less soreness and returned to near pre-exercise values by day 5 (124). Clarkson et al. compared 20 novice and experienced, young and older adult female exercisers (10 young, age: 23.6 &#xB1; years; 10 older, age: 67.4 &#xB1; 5.3 years) immediately, 1 day, 2 days, 3 days, 4 days, and 5 days post-exercise. Participants completed eccentric bicep curls, 1 set/session, 24 reps/set, 115% MVIC, short (12 sec) rest between reps, and a moderate (3 sec) rep tempo, for 2 sessions with 7 days rest between sessions. The findings demonstrated that DOMS increased significantly post-exercise following both sessions. Following session 1, young exercises exhibited peak soreness 1 day post-exercise, with a gradual decrease in soreness to near pre-exercise values on days 4 and 5. Following the 2nd session, young exercisers exhibited significantly less soreness, peaking 1 day post-exercise, and returning to near pre-exercise values on days 2 and 3. Elderly exercisers exhibited significantly more soreness following session 1, exhibiting peak values 2 days post-exercise, but returning to near pre-exercise values on days 4 and 5. Following the 2nd session, elderly exercisers exhibited the smallest increases in DOMS, peaking 1 day post-exercise, but maintaining values that were near pre-exercise values throughout the reassessment period (24). These studies suggest that older adults are likely to experience higher peak DOMS, and potentially a slower recovery rate when compared to young adults; however, this is not always the case. Further, young adults and older adults exhibit similar reductions (improvements) in DOMS and an increase in recovery rate with repeated sessions.
Adolescents Compared to Young Adults:
One study by Chen et al. compared 39 novice male exercisers (pre-adolescents age: 9.4 &#xB1; 0.5 years, adolescents age: 14.3 &#xB1; 0.4 years, adults age: 22.6 &#xB1; 2.0 years) immediately and 1 time a day for 5 days post-exercise. Participants completed eccentric elbow flexion via an isokinetic dynamometer, 5 sets/exercise, 6 reps/set, a short (10-sec) rest between reps, moderate (2 min) rest between sets, and a moderate (90&#xB0;/sec) rep tempo. Note, participants completed two exercise sessions separated by 3 weeks. Results demonstrated that the first bout of exercise resulted in a large decrease in concentric force production immediately following the exercise protocol, followed by gradual improvement during each reassessment, and pre-exercise values were not reached during the 5 day re-assessment period. The second bout resulted in a smaller decrease in force production, gradual recovery during the re-assessment period, and pre-exercise values were attained on the 5th day. Adult exercisers exhibited significantly larger decreases in strength when compared to adolescents and pre-adolescents. Additionally, following the first bout of exercise, adolescent and pre-adolescent exercisers exhibited a significant increase in DOMS 24 hours post-exercise, which peaked 2 days post-exercise, improved on days 3 and 4, and was near pre-exercise levels on day 5. Adult exercisers exhibited much larger increases in DOMS 1 day post-exercise, which peaked on days 2 and 3, and only started to improve by day 5. Following the 2nd bout of exercise adolescent and pre-adolescent exercisers exhibited significantly less DOMS which peaked 24 hours post-exercise, and reached near pre-exercise values by day 3 or day 4. Adult exercisers exhibited significantly more DOMS than adolescents and preadolescents following the second bout; however, those values were significantly less than the first bout, peaked 24 hours post-exercise, and continued to improve until reaching near pre-exercise levels on day 5 (17). In summary, adult exercisers exhibited significantly larger decreases in strength, increases in DOMS, and slower recovery rates than pre-adolescent or adolescent exercisers; however, all exercisers exhibited significant improvements following the 2nd session.

Recovery Time: DOMS, Gender, and Age

Additional Topics

<h3>Summary</h3>
<ul>
 <li>Frequency:&#xA0;<span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;"> Average and peak EMG activity may be reduced for several days following an initial resistance training session, with peak decreases potentially occurring 2 days post-exercise, and requiring up to 7 days to return to pre-exercise values. However, this decrease may only occur during initial sessions. Additionally, the number of days of rest between sessions is likely to have a significant effect on exercise volume (reps x sets x load), but may not have a significant effect on peak or average EMG activity. Last, improvements in maximal EMG activity may be correlated with an increase in 1-RM strength and require an extended training period of 1-2 sessions/week.</li>
 <li>Age: Post-exercise reductions in average and peak EMG activity may not be strongly correlated with force production or soreness, and peak reductions in EMG activity may occur hours or 1-2 days post-exercise. Novice exercisers are likely to exhibit larger reductions in EMG activity than experienced exercisers, young and middle-aged adults are likely to exhibit similar reductions, and older individuals may exhibit larger reductions than young and middle-aged individuals.</li>
 <li>Contraction Type, Tempo, and Forced Reps: Larger post-exercise reductions in peak EMG activity (and TMS) may be exhibited following eccentric contractions (when compared to concentric or isometric contractions), and/or slower rep tempos (longer time under <a id="tension" data-tip="1229" target="_blank" href="/glossary-term/tension" class="glossary">tension</a>). Conversely, an increase in load may not have a significant effect on post-exercise EMG activity.&#xA0;</li>
</ul>
<h3>Frequency</h3>
Several studies imply that the frequency of resistance training may have a significant effect on fatigue, recovery, and EMG activity. An RCT by Walker et al. compared 38 older novice female exercisers (age: 64-75 years) following an introductory resistance training program for 12 weeks with a frequency of 2x/week, and then random assignment to 24 weeks of a control group (no exercise), 1x/week group, or 2x/week group. The resistance training routine included a full body program (leg press, knee extensions, leg curls, chest press, lat pulldowns, shoulder press, seated rows, biceps curls, triceps pushdowns, abdominal curls, and back extensions). The 12-week introductory period included 2x/week, of at least 1 set/exercise, 14-20 reps to failure/set, 50-60% of 1-RM loads, short (1 min) rest between sets, and a moderate (2:0:2) rep tempo. The 24-week intervention period included 1x/week or 2x/week, 2-5 sets/exercise, 4-12 reps/set, 30-90% of 1-RM loads, and a moderate (1-3 min) rest between sets. Results demonstrated that the initial training period resulted in an increase in vastus lateralis and vastus intermedius cross-sectional area (CSA), and the experimental period resulted in a slight decrease in CSA for the 1x/week group and maintenance of CSA for the 2x/week group. Leg press 1-RM strength and peak EMG activity increased during the introductory period, and both groups exhibited similar and significant increases during the experimental period (4). Hortob&#xE1;gyi et al. compared 9 male and 9 female novice exercisers (age: 22.6 &#xB1; 2.7 years) 2 days, 4 days, and 7 days post-exercise. Participants were randomly assigned to a control group (no exercise) or an exercise group that completed 2 sessions separated by 2 weeks. The exercise protocol included eccentric knee extensions, 10 sets/exercise, 10 reps/set, 80% of 1-RM loads, and long (3 min) rest between sets. When compared to controls and pre-exercise values, the findings demonstrated that following the first session, exercisers exhibited significant decreases in strength and DOMS, with some values failing to return to pre-exercise values 7 days post-exercise. Following the second session changes in strength and DOMS failed to reach statistical significance.<span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;"> Similarly, following the <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">first sessions exercisers exhibited a significant decrease in peak EMG activity of the vastus lateralis during dynamic knee extensions, with peak decreases 2 days post-exercise, and a return to near pre-exercise values 7 days post-exercise. Following the second session, no significant decreases were noted. An additional interesting finding related to neuromuscular activity,<span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;"> both sessions resulted in significant and similar increases in patellar tendon reflex amplitude, with and without the Jendrassik maneuver, and the increases were still present 7 days post-exercise (74). Last, and perhaps most pivotal for frequency recommendations, Paz et al. compared 15 experienced male exercisers (age: 28. 1 &#xB1; 4.3 years) randomly assigned to 24, 48, or 72 hours of rest between 2 sessions. Both sessions included bench press and incline bench press (30 degrees), for 4 sets/exercise, 8 reps to failure/set, and moderate (2 min) rest between sets. Compared to the first session, bench press and incline bench press volume (reps x sets x load) were significantly reduced following 24 hours of rest, but similar following 48 or 72 hours of rest. Average EMG activity of the pectoralis major, <a id="anterior" data-tip="1566" target="_blank" href="/glossary-term/anterior" class="glossary">anterior</a> deltoid, and triceps brachii were similar following the 1st and 2nd sessions, regardless of the rest period. And, average EMG activity of the biceps brachii was higher during the 2nd session; however, the increase was similar following all rest periods (133). <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">These studies imply that average and peak EMG activity may be reduced for several days following an initial resistance training session, with peak decreases potentially occurring 2 days post-exercise, and requiring up to 7 days to return to pre-exercise values. However, this decrease may only occur during initial sessions. Additionally, the number of days of rest between sessions is likely to have a significant effect on exercise volume (reps x sets x load), but may not have a significant effect on peak or average EMG activity. Last, improvements in maximal EMG activity may be correlated with an increase in 1-RM strength and require an extended training period of 1-2 sessions/week.&#xA0;
<h3>Comparing Age</h3>
Research has compared changes in EMG activity following resistance training for young, middle-aged, and older adults. Fernandes et al. compared 27 male participants, divided into 9 young experienced exercisers (age: 21-25 years), 9 middle-aged experienced exercisers (aged: 35-54 years), and 9 middle-aged novice exercisers (aged: 35-53 years). Participants completed squats, 10 sets/exercise, 10 reps/set with 60% 1-RM, reps to failure/later sets, and moderate (2 min) rest between sets. The findings demonstrated that 1 day post-exercise all groups exhibited significant and similar decreases in squat peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> at 80% and 20% of 1-RM loads, and knee extension MVIC. 3 days post-exercise small reductions were still present. DOMS followed a similar trend; however, middle-aged novice exercisers exhibited significantly more soreness 1 day and 3 days post-exercise. Quadriceps maximum voluntary EMG activity decreased similarly for young and middle-aged experienced exercisers with the largest decreases exhibited on the 2nd and 3rd day post-exercise. Similar trends were noted for middle-aged novice exercisers; however, the decrease was significantly larger 1 day and 3 days post-exercise (18). <span style="color: #000000; background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Hakkinen compared 8 young (age: 25.0 &#xB1; 1.4 years), 7 middle-aged (age: 48.0 &#xB1; 3.7 years), and 8 older (age: 68.9 &#xB1; 3.2 years) novice female exercisers, 1 hour, 2 hours, 1 day and 2 days post-exercise. All participants performed the leg press for 5 sets/exercise, 10 reps to failure/set, 70% of 1-RM load, and long (3 min) rest between sets. Results demonstrated that all exercisers exhibited a shift in the rate of force development and maximal EMG activity immediately post-exercise and returned to pre-exercise values within 2 hours; however, the elderly exercisers exhibited another decrease in force production and EMG activity 24 hours post-exercise (126). Last, Heckel et al. compared 10 young and 10 elderly physically active men (age: 25. 1 &#xB1; 4.9 years and 64.5 &#xB1; 5.5 years) 1 day, 2 days, 7 days, and 15 days post-exercise. This study required participants to complete 6 sessions throughout a 15-day period, with sessions completed on day 1, day 3, day 5, day 8, day 10, and day 12. Participants completed right leg knee extensions via an isokinetic dynamometer, 4 sets/session, 15 reps/set, short (1 sec) rest between reps, moderate (2 min) rest between sets, and moderate (60&#xB0;/sec) rep tempo. Testing was completed on day 1, day 2, day 3, day 8, and day 15. The findings demonstrated that only the young men exhibited a significant decrease in the rate of force development and only following the 1st session. Older men exhibited larger increases in DOMs; however, both groups exhibited peak soreness on the 7th day, and had returned to near 1st session values by day 15. Finally, only elderly men exhibited a decrease in quadriceps peak EMG activity and only during the 1st week (22). These studies imply that post-exercise reductions in average and peak EMG activity may not be strongly correlated with force production or soreness, and peak reductions in EMG activity may occur hours or 1-2 days post-exercise. Novice exercisers are likely to exhibit larger reductions in EMG activity than experienced exercisers, young and middle-aged adults are likely to exhibit similar reductions, and older individuals may exhibit larger reductions than young and middle-aged individuals.
<h3>Contraction Type, Tempo, and Forced Reps:&#xA0;</h3>
A few studies have investigated EMG activity post-exercise comparing contraction type, tempo, and forced reps. <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">As mentioned above, Thomas et al. compared 10 experienced male exercisers (age: 21 &#xB1; 2 years) 1 day, 2 days, and 3 days post-exercise. Participants completed squats, jump squats, and maximal sprints during 3 separate sessions, 1 week apart, in randomized, counter-balanced order, with each session followed by 4 days of <a id="assessment" data-tip="1478" target="_blank" href="/glossary-term/assessment" class="glossary">assessment</a>. The squat session included 10 sets/exercise, 5 reps to failure/set, 80% of 1-RM loads, long (3 min) rest between sets, and a moderate (2:0:MaxV) rep tempo (note: if the concentric phase was 2 sec or longer the set was discontinued). The jump squat session included 10 sets/exercise, 5 reps/set, 10 &#xB1; 5kg load, intent to achieve maximal height, and long (3 min) rest between sets. The maximal sprints session included 15 sets/exercise, a distance of 30 meters/set, and moderate (2 min) rest between sets. The findings demonstrated that compared to pre-exercise values, all groups exhibited peak fatigue immediately following exercise, peak DOMS 1 day post-exercise, and a return to near pre-exercise values 3 days post-exercise. The squat protocol exhibited larger reductions in MVIC both immediately and 24 hours post-exercise when compared to the jump squats and sprint protocols, but all groups returned to pre-exercise values 72 hours post-exercise. All protocols exhibited the largest decreases in maximum voluntary EMG activity (leg extensions) immediately post-exercise; however, the squat protocol resulted in the largest decrease, and a return to pre-exercise values was exhibited 72 hours post-exercise, compared to the jump squats and sprints protocol recovering in 48 hours. Voluntary activation with transcranial <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> activation (TMS) of the rectus femoris was also assessed at 50%, 75%, and 100% of MVC, decreased most for all protocols immediately post-exercise, the squat and sprint protocols resulted in the largest immediate decreases, and a return to pre-exercise values was exhibited 48 hours after the squat and sprint protocols, but 24 hours after the jump squats protocol (34). Kroon et al. compared 5 novice male exercisers (age: 20-35 years) 0.75 hours and 1x/day (up to 10 days) following 3 bicep curl protocols (isometric, concentric, or eccentric contractions) each separated by 3 weeks, performed on an isokinetic dynamometer. Each bicep curl protocol included 3 sets/session, 10 reps-to-failure/set, rep tempo was a 3-sec contraction followed by 2-sec rest, with short (1 min) rest between sets. The findings demonstrated that when compared to pre-exercise values, biceps brachii rate of increase and peak EMG activity were reduced for a longer time (average 7 days) following eccentric curls when compared to concentric (average 4.5 days) and isometric curls (average 1.5 days) (115). Last, Ahtiainen et al. compared 16 experienced male exercisers (age: 26.8 &#xB1; 3.5 years) 1 day, 2 days, and 3 days post-exercise. Participants completed two protocols separated by 14 days, including a 12-RM/set protocol and a &quot;forced reps&quot; protocol with a heavier load ensuring that assistance was needed during the last 3-5 reps. Participants completed 4 sets of leg press, 2 sets of squats, and 2 sets of knee extensions, with moderate (2 min) rest between sets, and long (4 min) rest between exercises. The findings demonstrated that the forced reps protocol resulted in larger decreases in knee extension MVIC post-exercise compared to the 12 RM/set protocol; however, neither protocol resulted in a significant decrease in maximal voluntary EMG activity during any re-assessment period (14). These studies imply larger post-exercise reductions in peak EMG activity (and TMS) may be exhibited following eccentric contractions (when compared to concentric or isometric contractions), and/or slower rep tempos (longer time under <a id="tension" data-tip="1229" target="_blank" href="/glossary-term/tension" class="glossary">tension</a>). Conversely, an increase in load may not have a significant effect on post-exercise EMG activity.&#xA0;

Frequency and Recovery Time: EMG Activity

Frequency: Bone Mineral Density, Resting Blood Pressure, Functional Testing, and Psychosocial Improvements

<h3>Summary</h3>
<ul>
 <li>Lumbar Extension Programs: <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Low back strength, pain, and disability improve more following lumbar extension exercise frequency of 1x/week when compared to 0.5x/week (1 time every other week). Although a frequency of 1 - 3x/week during an initial training period (e.g. initial 12 weeks) may result in similar improvements for some outcome measures, it is likely that 2 - 3x/week is <a id="superior" data-tip="1570" target="_blank" href="/glossary-term/superior" class="glossary">superior</a> to 0.5 - 1x/week for improving dynamic strength, pain, and function. Further, at least 1x/week is required to maintain benefits beyond the initial training period, and 2 - 3x/week is likely necessary to continue improving.&#xA0;</li>
 <li>Neck, Shoulders, and Core: <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Shoulder exercises performed 1x/day or 2x/day may have similar effects on neck and shoulder pain. <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">However, performing neck and trunk exercises 2 - 3x/week will likely result in significantly larger strength improvements than 1x/week.&#xA0;&#xA0;</li>
</ul>
<h3>Lumbar Extension Programs</h3>
Several studies compare the effects of lumbar extension routine frequency on low back pain, strength, and function. An RCT by Bruce-Low et al. compared 72 participants (age: 45.5 &#xB1; 14.1 years), with unreported exercise experience and chronic low-back pain, randomly assigned to a control group (no activity), a 1x/week group, or a 2x/week group. Participants performed lumbar extensions on a machine for 12 weeks, 1 set/session, 8-12 reps/set, a slow (4:0:2) rep tempo, and the 1x/week group using loads equal to 80% maximum voluntary isometric contraction (MVIC) loads, and the 2x/week group using 50% MVIC 1x/week and 80% MVIC 1x/week. Results demonstrated that both groups exhibited similar improvements in MVIC strength (isometric lumbar extension strength at 0&#xB0;, 12&#xB0;, 24&#xB0;, 36&#xB0;, 48&#xB0;, 60&#xB0; and 72&#xB0; of lumbar flexion), range of motion (ROM) (note, the study did not disclose the <a id="specificity" data-tip="1224" target="_blank" href="/glossary-term/specificity" class="glossary">specific</a> range of motion measurements), Schober&apos;s <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">Test</a>, visual analog scale pain scores, and the Oswestry disability index scores (136). An RCT by Graves et al. compared 114 novice exercisers (age: 28 +/- 9 years) randomly assigned to a control (no exercise), 0.5x/week (1x every other week), 1x/week, 2x/week, or 3x/week groups performing dynamic strengthening, and one group performing 1x/week with isometric strengthening. All participants completed seated lumbar extensions for 12 weeks, 8-12 reps to fatigue/set, and a slow (4:0:2:1) rep tempo. Results demonstrated that all groups exhibited similar improvements in lumbar extension MVIC strength; however, the 1x/week (isometric and dynamic), 2x/week, and 3x/week groups exhibited larger increases in training load (dynamic strength) than the 0.5x/week group (137). <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Tucci et al. compared 50 novice exercisers (age: 34 &#xB1; 11 years) randomly assigned to a 1x/week group, 2x/week group, or 3x/week group for 12 weeks. All participants performed lumbar extensions for 8-12 RM/set, but were divided into groups performing different volumes and contraction types including; 2 sets/dynamic, 2 sets/isometric, 2 sets/1 set of each, 1 set/dynamic, and 1 set/isometric. Participants then performed 12 weeks of training, followed by 12 weeks of detraining, and detraining included randomization into a control group (no exercise), 0.5x/week group, or 0.25x/week group (1 session every 4 weeks). The r<span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">esults demonstrated similar increases in lumbar extension isometric strength following the initial 10-12 weeks of exercise; however, despite both detraining groups maintaining some strength improvement the 0.5x/week exhibited an average of 2.2% reduction in isometric strength, and the 0.25x/week group exhibited an average of 17.5% reduction in strength (138). Last, a<span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">n RCT by Kim et al. compared 40 males (aged: 30-52 years) following discectomy, then 6 weeks of rest, then an initial 12-week program (2x/week), and then 12 weeks of an experimental protocol in which participants were randomized into four groups: a control group (no exercise), 0.5x/week group (every other week), 1x/week group, and 2x/week group. <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">The training routine included lumbar extensions, 2 sets/session, and 15 reps/set, with a rep tempo of 24&#xB0;/sec. The findings demonstrated that the 2x/week group was the only group to exhibit additional reductions in visual analog scale (VAS) pain scores, only the 1x/week and 2x/week groups exhibited additional improvements in lumbar extension isometric strength and Oswestry Disability Index scores, and the 0.5x/week group and control groups exhibited a decrease in strength and no changes in Oswestry Disability Index scores (139). In summary, these studies imply that low back strength, pain, and disability improve more following lumbar extension exercise frequency of 1x/week when compared to 0.5x/week (1 time every other week). Although a frequency of 1 - 3x/week during an initial training period (e.g. initial 12 weeks) may result in similar improvements for some outcome measures, it is likely that 2 - 3x/week is <a id="superior" data-tip="1570" target="_blank" href="/glossary-term/superior" class="glossary">superior</a> to 0.5 - 1x/week for improving dynamic strength, pain, and function. Further, at least 1x/week is required to maintain benefits beyond the initial training period, and 2 - 3x/week is likely necessary to continue improving.&#xA0;
<h3>Neck, Shoulders, and Core</h3>
Additional studies have compared training frequencies for shoulder, neck, and core exercises. An RCT by Saeterbakken et al. compared 20 women and 7 men (age: 48.7 &#xB1; 11.8 years) with current neck or shoulder pain. Following an 8-week control period (no exercise), participants were randomized into groups performing exercise 1x/day or 2x/day for 8 weeks. The exercise program was designed to last about 10 minutes and included 4 upper extremity exercises (one arm rows, upright rows, one arm reverse flies, and one arm <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> raise), 2 sets/exercise, 12-15 RM/set for weeks 1-4, 1-10 RM/set for weeks 5-8, and amount of resistance progressively increased to maintain rep ranges (band resistance). The results demonstrated that the 2 groups exhibited similar improvements in neck pain and health-related quality of life scores (HRQL), and neither group exhibited improvements in shrug or row MVIC (140). An RCT by Pollock et al. compared 50 male (aged: 36&#xB1; 9 years) and 28 female (age: 30 &#xB1; 9 years) novice exercisers following a 12-week intervention. Participants were randomized into 5 groups: control (no exercise), 1x/week isometric, 1x/week dynamic, 2x/week isometric, or 2x/week dynamic. All participants completed cervical extensions, either dynamically with 8-12 rep-to-failure/set and a slow (4:1:2) rep tempo, or isometrically at flexion angles of 0&#xB0;, 18&#xB0;, 36&#xB0;, 54&#xB0;, 72&#xB0;, 90&#xB0;, 108&#xB0;, and 126&#xB0;. The findings demonstrated that isometric and dynamic contractions resulted in similar improvements in maximal voluntary isometric contraction (MVIC) strength; however, groups performing the protocol 2x/week exhibited significantly larger improvements than 1x/week (141). An RCT by DeMichele et al. compared 33 male and 25 female novice exercisers (age: 28.6 &#xB1; 8.8 years) randomly assigned to a control group (no exercise), or groups performing exercise 1x/week, 2x/week, or 3x/week. All exercisers completed seated torso rotations on a machine for 12 weeks, 1 set/exercise, 8-12 RM/set, and a slow (4:3:1) tempo. Results demonstrated that torso rotation MVIC did not significantly improve for the control (no exercise) group or 1x/week group; however, similar and significant improvements were exhibited by the 2x/week group and the 3x/week groups. <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Additionally, the dynamic resistance used during training increased significantly more for the 2x/week group and 3x/week group when compared to the 1x/week group (142). T<span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">hese studies imply that shoulder exercises performed 1x/day or 2x/day may have similar effects on neck and shoulder pain. <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">However, performing neck and trunk exercises 2 - 3x/week will likely result in significantly larger strength improvements than 1x/week.&#xA0;&#xA0;
<img alt="Cuing the abdominal-drawing in maneuver (ADIM) when in quadruped position, may increase transverse abdomens and intrinsic stabilizer activity." title="Training the core muscles 2 - 3x per week likely increases the strength of the core muscles" src="https://www.datocms-assets.com/25800/1687326097-screenshot-2023-06-20-at-10-40-42-pm.png">

Frequency: Rehabilitation and Core Muscle Exercise

<h3>Summary</h3>
<ul>
 <li>Individual Differences: <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Different individuals, both novice and experienced, can exhibit dramatically different post-exercise recovery times for strength, soreness, arm circumference, ROM, and serum concentrations of markers of <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> damage and inflammation. Individuals may also exhibit different amounts of adaptation and improvement in recovery times between the 1st and 2nd sessions of the same routine. Further, an exerciser&apos;s perception of recovery may lag behind objective measures of recovered strength on subsequent days.</li>
</ul>
<h3>Soreness and Endurance</h3>
<span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Several studies have demonstrated that the magnitude and duration of post-exercise changes, and the subsequent recovery, can vary significantly between individuals. <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Jones et al. compared 10 experienced male exercisers (age: 21.8 &#xB1; 3.94 years) 2, 3, 4, and 5 days post-exercise, following 2 sessions. Both sessions included a full body program (bench press, bicep curls, tricep press, lat pulldowns, leg press, and leg curls) 3 sets/exercise, 10 reps to failure/set, and moderate (2 min) rest between sets. This study considered participants recovered once they could approximate their 10-RM performance for each exercise. The findings demonstrated that 7/10 participants recovered 2 days post-exercise following both sessions, and 1/10 recovered 3 days post-exercise following both sessions. Additionally, 1/10 recovered 4 days post-exercise following the first session, and 2 days post-exercise following the second session. And, 1/10 did not recover within 5 days post-exercise following the first session but did recover 4 days post-exercise following the second session (143). <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Kroon et al. compared 5 novice male exercisers (age: 20-35 years) during reassessment 0.75 hours and 1x/day for 10 days, following 3 bicep curl protocols (isometric, concentric, or eccentric contractions) performed on an isokinetic dynamometer, with 3-weeks rest between sessions. Each bicep curl protocol included 3 sets/session, 10 reps-to-failure/set, rep tempo was a 3-sec contraction followed by 2-sec rest, with short (1 min) rest between sets. The findings demonstrated significantly larger changes in post-exercise biceps brachii EMG activity, ROM, and soreness following eccentric curls, less change following isometric curls, and the least change following concentric curls. However, significant individual differences were noted; for example, post-exercise soreness following the eccentric biceps curls protocol resulted in 5 participants being sore for 4 days, 4 for 5 days, 2 for 8 days, and none for 9 days; following isometric curls 5 participants were sore for 2 days, 3 for 3 days, and none for 4 days; and following concentric curls, 3 participants were sore for 2 days, and none for 3 days (115). Korak et al. compared 10 experienced male exercisers (age: 26 &#xB1; 6 years) 1 day and 2 days post-exercise. Participants completed a full body program (bench press, dumbbell military press, deadlifts, leg press, knee extensions, tricep extensions, dumbbell <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> raises, chest flyes, hip abductions, and hip adductions), 2 sets/exercise, 8 reps to failure/set, moderate (1.5 min) rest between sets, and moderate (2 min) rest between exercises. Recovery was defined as performing a set with a 10-RM load within 1 rep of pre-exercise totals. The findings demonstrated <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">significant individual differences in recovery (detailed findings below); however, some trends may be implied. The findings suggest that experienced male exercisers exhibit shorter recovery times for single-joint exercise when compared to compound exercises, and shorter recovery times for lower-body exercises when compared to upper-body exercises. Additionally, although the objective measures of recovery demonstrated significant differences between the 1st and 2nd-day post-exercise, the average score for the perception of recovery was similar for both days (144). These studies demonstrate that even experienced exercisers can exhibit significant individual differences in recovery rates for soreness and strength and potentially different amounts of adaptation and improvement in recovery rates between the 1st and 2nd sessions of the same routine. Further, an exerciser&apos;s perception of recovery may lag behind objective measures of recovered strength on subsequent days.
<h3><span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Post-Exercise Serum Concentrations of Markers of Muscle Damage</h3>
<span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Additional studies demonstrate that significant individual differences can be exhibited for post-exercise serum concentrations of creatine kinase. De Castro et al. compared 9 experienced male exercisers (aged: 21.3 &#xB1; 1.6 years) 1 day, 2 days, and 3 days post-exercise. Participants completed a full body program (exercises for the latissimus dorsi, pectoralis major, deltoids, triceps brachii, biceps brachii, quadriceps, hamstrings, and gastrocnemius), for 3 sets/exercise, 10 reps to failure/set, and moderate (1.5 min) rest between sets. <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">The findings demonstrated that serum concentrations of creatine kinase were significantly elevated post-exercise, peaked 1-2 days post-exercise, and most participants returned to near pre-exercise levels within 2 days; however, 2 participants required longer than the 3-days (145). Damas et al. compared 286 novice male exercisers (aged: 18-27 years) immediately, 1 day, 2 days, 3 days, 4 days, and 5 days post-exercise. Participants completed eccentric elbow flexion via an isokinetic dynamometer, 1 set/exercise, 30 reps/set, short (10-12 sec) rest between reps, and a slow (30&#xB0;/sec: 1 sec: None) rep tempo. Note, participants were clustered into three categories based on the post-exercise percent decrease of their maximum voluntary concentric contraction (MVCC): low responder (n=61), moderate responder (n=152), and high responder (n = 73). The findings demonstrated significant differences between groups for MVCC, DOMS, arm circumference, and ROM, with high responders exhibiting higher peak values and longer times to recovery (return to pre-exercise values) for all outcome measures. Serum concentrations of creatine kinase increased for all participants; however, statistically significant differences between groups were observed for days 3, 4, and 5. The high responders exhibited peaks on day 4 that were nearly double moderate responders, and they still exhibited higher concentrations on day 5 than were exhibited by any other group at any time point. Moderate responders also peaked on day 4 but exhibited lower values than high responders, and low responders only exhibited statistically significant increases in serum concentrations on day 5 (146). <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">These studies demonstrate that different individuals, both novice and experienced, can exhibit dramatically different post-exercise MVIC, DOMS, arm circumference, ROM, and serum concentrations of markers of <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> damage and inflammation. Although trends can be derived from the research regarding likely contributors to larger changes or longer recovery times, significant individual differences are likely.&#xA0;
<span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;"><img alt="How often should an individual perform back squats" title="A female athlete performing the back squat " src="https://www.datocms-assets.com/25800/1687887249-squat-girl.jpg">
Findings from Korak et al. (2015):
<ul>
 <li>The percentage of participants recovered 1-day post-exercise was 80% for hip abduction and adduction; 70% for tricep extensions; 60% for the bench press, military press, leg press, knee extensions, and chest flies; and 50% for deadlifts and dumbbell <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> raises. 2 days post-exercise, the percentage of participants recovered was 100% for tricep extensions; 90% for military press, knee extensions, chest flies, and dumbbell <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> raises; 80% for leg press, hip abduction, and hip adduction; 70% for the bench press; and 60% for deadlifts.</li>
 <li>The percentage of participants who recovered from compound exercises 1-day post-exercise was 30%, and 2 days post-exercise was 70%. And, recovery for isolation exercises 1 day post-exercise was 50%, and 2 days post-exercise was 80%.&#xA0;</li>
 <li>The percentage of participants who recovered for upper body exercises 1 day post-exercise was 40%, and 2 days post-exercise was 80%. And, recovery for lower body exercises at 1 day post-exercise was 60%, and 2 days post-exercise was 80%.</li>
 <li>The percentage of participants who recovered from all exercises 1 day post-exercise was 50% and at 48 hours post-exercise was 80%.</li>
 <li>Perceived recovery was rated with a 0-10 scale, 10 was fully recovered, and values are expressed as the average score for the group. Perceived recovery for upper body exercise 1 day post-exercise was ~6/10 and 2 days post-exercise was ~6.5/10, lower body exercise 1 day post-exercise was ~5.5/10, and 2 days post-exercise was ~7/10; compound exercises 1 day post-exercise was ~5.5/10, and 2 days post-exercise was ~6.5/10, and, isolation exercise 1 day post-exercise was ~6.5/10, and at 2 days post-exercise was ~7/10.</li>
</ul>

Recovery Time: Individual Differences

<h3>Summary:</h3>
<ul>
 <li><span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">Work, EMG activity, Lactate Concentrations, and Days Rest: These studies were considered pivotal due to their <a id="relevance" data-tip="1504" target="_blank" href="/glossary-term/relevance" class="glossary">relevance</a> in making <a id="evidence-based-practice" data-tip="1538" target="_blank" href="/glossary-term/evidence-based-practice" class="glossary">evidence-based</a> recommendations on days rest between sessions and session frequency. Based on these studies, the number of days of rest between sessions has no influence on EMG activity, 1-day of rest before a 2nd session is likely to result in a significant decrease in the volume of work and higher blood serum concentrations of lactate immediately post-exercise, 2 days of rest is likely to result in similar lactate concentrations and similar work, and 3 of days rest may result in an increase in work performed.</li>
</ul>
Two studies were located that directly compared performance during a subsequent session with 1 - 3 days of rest. Paz et al. compared 15 experienced male exercisers (age: 28. 1 &#xB1; 4.3 years) randomly assigned to 1 day, 2 days, or 3 days of rest between 2 sessions. Both sessions included bench press and incline bench press (30 degrees), for 4 sets/exercise, 8 reps to failure/set, and moderate (2 min) rest between sets. The findings demonstrated that the EMG activities of the pectoralis major, <a id="anterior" data-tip="1566" target="_blank" href="/glossary-term/anterior" class="glossary">anterior</a> deltoid, triceps brachii, and biceps brachii were similar regardless of the rest period. A statistically significant increase in EMG activity of the biceps brachii was noted during the second session; however, the increase was similar for all protocols. Conversely, bench press and incline bench press volume (reps x sets x load) were significantly different between protocols, resulting in a significant reduction in volume during the second session following 1 day of rest, but similar to the first session following 2 days or 3 days of rest (147). Miranda et al. compared 16 experienced male exercisers (age: 26.1 &#xB1; 3.1 years) randomly assigned to 1 day, 2 days, or 3 days rest between the 1st and 2nd session. Sessions included bench press performed with 0&#xB0; (flat bench), 30&#xB0;, or 45&#xB0; inclines, 4 sets/position, 8 RM load/set, reps to failure/set, and moderate (2 min) rest between sets. The results demonstrated that 2-3 days were necessary to perform similar total work (sets x reps) during the re-assessment of the flat or incline (30&#xB0; or 45&#xB0;) bench press. 1-day rest resulted in a significant decrease in total work, and 3 days of rest resulted in more total work than 2 days of rest. Additionally, blood lactate concentrations immediately post-exercise were compared following the first and second sessions. The findings demonstrated that 1 day of rest between sessions resulted in significantly higher blood lactate concentrations; however, 2-3 days of rest resulted in similar concentrations<span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;"> (116). These studies were considered pivotal due to their <a id="relevance" data-tip="1504" target="_blank" href="/glossary-term/relevance" class="glossary">relevance</a> in making <a id="evidence-based-practice" data-tip="1538" target="_blank" href="/glossary-term/evidence-based-practice" class="glossary">evidence-based</a> recommendations on days rest between sessions and session frequency. Based on these studies, the number of days of rest between sessions has no influence on EMG activity, 1-day of rest before a 2nd session is likely to result in a significant decrease in the volume of work and higher blood serum concentrations of lactate immediately post-exercise, 2 days of rest is likely to result in similar lactate concentrations and similar work, and 3 of days rest may result in an increase in work performed.
<ul></ul>

Pivotal Studies: Work, EMG activity, Lactate Concentrations, and Days Rest

Bibliography

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Copyright

A-Band - Refers to the part of the muscle cell that looks darker under a microscope.  This area of the cell is darker due to parallel arrangement of thicker filaments (myosin) and overlap with the thinner filaments (actin).
<ul>
 	<li>As a muscle contracts, the A-band is where actin and myosin interact.</li>
</ul>
<ol>
 	<li>Saladin, K. (2014). Anatomy &amp; physiology: The unity of form and function. McGraw-Hill Higher Education, New York. ISBN: 9780073403717</li>
</ol>

Accuracy - the proportion of individuals correctly identified by the test results.
<ul>
 	<li>For example, a special test with perfect accuracy would imply a test has 100% specificity, 100% sensitivity, 100% positive predictive value and 100% negative predictive values.</li>
</ul>

Action Potential - A rapid change in voltage, resulting in a wave of excitation, that may result in stimulation of a nerve or muscle cell.
<ul>
 	<li>In order for an action potential to be initiated, the resting membrane voltage must exceed the excitation threshold, which then results in a cascade of depolarization and the "wave of excitation." Any stimulus below that threshold will not result in an action potential, and a stimulus greater than the threshold will not increase a single action potential, but may result in additional action potentials.  In this way, the action potential functions more like an on/off switch (all or none), and less like a dimmer switch.</li>
</ul>

A single-joint movement pattern (most often) designed to load a specific under-active muscle(s), while minimizing the contribution of over-active synergists via specific cues/joint motions.
<ul>
 	<li style="text-align: left;">Activation techniques/exercises are performed with the intent of addressing a muscle exhibiting a reduction in activity (tone) as a result of, or contributing to postural dysfunction.</li>
 	<li style="text-align: left;">Activation techniques/exercises cannot be multi-joint movement patterns due to relative flexibility, altered reciprocal inhibition, and synergistic dominance resulting in compensation patterns.</li>
</ul>
Example, <a href="https://brentbrookbush.com/articles/corrective-exercise-articles/activation/gluteus-medius-activation-progression/" target="_blank">gluteus medius activation</a> involves resisted hip abduction while minimizing the contribution of the TFL via hip extension.

Active stretching is a term used to describe a stretch that involves an active contraction of opposing musculature to lengthen a muscle to its end range. Generally these stretches are held for 2-5 seconds and repeated for 8-15 repetitions.

Adenosine triphosphatase (ATPase): is the enzyme responsible for catalyzing (initiating and accelerating) the decomposition of ATP to ADP.
<ul>
 	<li>This dephosphorylation (breakdown) reaction releases energy for processes like muscular contraction.</li>
</ul>

Adenosine triphosphate (ATP): The molecule that functions as a universal energy-transfer molecule, providing most of the energy associated with muscular contraction and human movement. ATP is composed of an adenine group, a ribose group, and three molecules of inorganic phosphates.
<ul>
 	<li>Energy is provided when hydrolysis results in the cleaving of a phophate group; resulting in adenosine diphosphate, an inorganigic phosphate group, and energy.</li>
</ul>

Algometry - measuring the amount of pressure to result in sensitivity or pain, using an algometer.
<ul>
 	<li>Generally, research uses algometry to establish a minimum pain pressure threshold (PPT), in which a lower PPT implies more sensitivity and pain, and a higher PPT implies less sensitivity and pain. PPT is a common outcome measure in trigger point research.</li>
</ul>
<a href="https://brentbrookbush.com/wp-content/uploads/2019/07/Algometer.jpg"><img class="aligncenter wp-image-140177" src="https://brentbrookbush.com/wp-content/uploads/2019/07/Algometer.jpg" alt="Image of an Algometer" width="500" height="333" /></a>

All-or-none principle - a nerve or muscle cell's response to a stimulus is independent of the strength of the stimulus. If that stimulus exceeds the threshold potential (threshold of an action potential), the nerve or muscle fiber will respond completely; otherwise, there is no response.

Example, when a motor unit in the biceps brachii is stimulated it contracts the same way whether a 10 lb or 50 lb dumbbell is lifted.  It is actually the number of muscle cells and the size of the motor unit that determines force output.

&nbsp;

The transition period between eccentric load and concentric contraction during a repetition of an exercise.  This term is most often used in reference to power/plyometric exercises, in which a shorter amortization phase is believed to be beneficial.  The shorter amortization phase may better use the stored energy from the elastic deformation of connective tissue and enhance synchronization of myotatic (stretch) reflex with maximum voluntary contraction.

Example, the athlete was cued to spend as little time as possible in the bottom of their squat stance (the amortization phase) during a set of box jumps.

Muscles that oppose the prime mover and synergists for a given joint action.

That is, all the muscles that can perform the opposing joint action.

Example: The triceps and anconeus are antagonists during elbow flexion.

An anatomical direction; toward the front

Example, the face is on the anterior aspect of the head

Appendicular Skeleton - referring to the bones the bones of the arms and legs, as well as the bones that support them. This includes the pelvis, clavicle and scapula. There are approximately 126 bones in the appendicular skeleton.
<ul>
 	<li>Etymology - Appendicular, as in appendage, "that which is appended to something as a proper part," 1640s, from <a class="crossreference" href="https://www.etymonline.com/word/append?ref=etymonline_crossreference">append</a> + <a class="crossreference" href="https://www.etymonline.com/word/-age?ref=etymonline_crossreference">-age</a>. - <a href="https://www.etymonline.com/word/appendage" target="_blank" rel="noopener">Etymology Online</a></li>
</ul>
"Appendicular skeleton" is a label referring to a set of bones whose function is distinct from the bones of the "<a href="https://brentbrookbush.com/glossary/axial-skeleton/" target="_blank" rel="noopener">axial skeleton</a>".

A reflexive decrease in muscle activity due to joint dyskinesis.
For example, a reduction in deep cervical flexor activity as a result of cervical spine dyskinesis.

Arthrokinematic Motion - Small amplitude motions between bone surfaces at a joint.  The arthrokinematic motions are roll, glide (slide or translation), spin, compression and distraction (traction). Arthrokinematic motions accompany osteokinematic motions to maintain joint congruence.
<ul>
 	<li>Example, arthrokinematic motion of the talus includes posterior glide on the tibia during ankle dorsiflexion.</li>
</ul>
Synonyms include: arthrokinematics, passive accessory motion, joint play and component motion

&nbsp;

Assessment - is the act of assessing, i.e. determining the importance, size, or value of -

In most cases, the results of an assessment are compared to normative data. If the individual exhibits values that are within normal parameters, it may be assumed that the aspect of health or motion assessed is not contributing to the patient's complaint, symptoms or movement impairment. If the results fall outside of normal parameters, it may indicate that the aspect of health or motion assessed is contributing to, or being affected by the patient/client's complaint, symptoms, or movement impairment. In some cases, the results of an assessment are compared to an "ideal model." In this case, deviations from the ideal are noted as potential issues. For example, deviations noted in the <a title="Introduction to the Overhead Squat Assessment" href="https://brentbrookbush.com/online-courses/articles/assessment/introduction-overhead-squat-assessment/" target="_blank">Overhead Squat Assessment</a> are compared to an "ideal model" of posture and motion.

Assessments used by human movement professionals can be divided into three broad categories:
<ul>
 	<li>"Clear" the Patient/Client for Intervention - These are tests, assessments and evaluations used to determine if a patient/client's issue may improve given the assessing professional's scope, skills, abilities and willingness to treat that individual.
<ul>
 	<li>For example, many of the special tests used in orthopedic medicine assist in determining the level of pathology or likelihood of a particular diagnosis. Certain issues and diagnoses are beyond the scope of the human movement professional, and are better treated by diagnostic professionals in the medical community (physicians, podiatrists, surgeons, etc.). A Calf Squeeze (Thompson) Test is one example, in which a positive sign may indicate a rupture of the Achilles tendon that may be better treated via surgical intervention.</li>
</ul>
</li>
 	<li>Highlight Contraindications - Tests, assessments and evaluations used to stratify risk or preclude a professional from addressing certain tissues, motions or using a particular technique.
<ul>
 	<li>For example, the Vertebral Artery Test (VBI) is often used to determine if high velocity thrust mobilizations (manipulations) are safe for a patient with cervical dysfunction.</li>
</ul>
</li>
 	<li>Refine Exercise/Intervention Selection: Tests, assessments and evaluations used to assist the professional in determining which techniques, modalities and exercises will best address a patient/client's complaints or desired goals.
<ul>
 	<li>Most movement assessments fall into this category. For example, a positive <a href="https://brentbrookbush.com/vimeo_videos/elys-test-rectus-femoris-flexibility-assessment/" target="_blank">Ely's Test</a> may indicate a need to release and/or lengthen the <a href="https://brentbrookbush.com/articles/anatomy-articles/muscular-anatomy/rectus-femoris/" target="_blank">rectus femoris</a>.</li>
</ul>
</li>
</ul>
Note: An assessment, or assessment result, may fall into more than one category. For example, although goniometry is an assessment most often used to Refine Exercise/Intervention Selection, if a range of motion is significantly altered, with an abnormal end-feel, and/or causes the patient or client/pain, the individual may need to be referred to a physician for further testing and Clearance to resume rehab activities.  Further, that same patient may return to the human movement professional with a list of Contraindicated Activities from the physician. - "When in doubt, refer out!"

Axial Skeleton - referring to the bones of the head, neck, trunk and spinal column (does not include pelvis). There are approximately 80 bones in the axial skeleton.
<ul>
 	<li>Etymology - Axial, as in "axis", referring to "imaginary motionless straight line around which a body (such as the Earth) rotates," from Latin axis "axle, pivot, axis of the earth or sky" - <a href="https://www.etymonline.com/word/axis" target="_blank" rel="noopener">Etymology Online</a></li>
</ul>
"Axial skeleton" is a label referring to a set of bones whose function is distinct from the bones of the "<a href="https://brentbrookbush.com/glossary/appendicular-skeleton/" target="_blank" rel="noopener">appendicular skeleton</a>".

Balance - The ability to maintain a body’s center of mass over its base of support. Balance can be static or dynamic.
<ul>
 	<li>For example, maintaining balance is harder on one leg because the center of mass must stay over a much smaller base of support.</li>
</ul>

A ball and socket joint (also called a spheroid joint or spheroidal joint) is a synovial joint in which the rounded or spherical end of one bone fits into a cup-like depression of another bone. The distal bone is capable of motion around an indefinite number of axes, which have one common center. Examples include the hip and shoulder (glenohumeral joint)

Base of support (BoS) - refers to the area beneath an object or person, and the area within the perimeter created by every point of contact that the object or person makes with the supporting surface. This may include the <a href="https://brentbrookbush.com/articles/anatomy-articles/muscular-anatomy/gluteus-maximus/" target="_blank" rel="noopener">glutes</a> of someone sitting on a chair, or the back of someone leaning against a wall.
<ul>
 	<li>For example, during a single leg balance the BoS is the area of the foot in contact with the surface; however, when a person is standing on two feet, the BoS is the area of both feet and the surface between them.</li>
</ul>

Pertaining to both sides

Example, bilateral rows are performed with both arms at the same time.

Case-control Study - a particular form of retrospective study that samples a matched group of people who have, and do not have the outcome being studied. A case-control study is a quasi-experimental design, often used in medicine to aid in determining potential contributing factors (cannot determine causality). In this study type exposure is the dependent variable and outcome is independent.
<ul>
 	<li>Example, in this retrospective case-control, medical records were investigated for trends correlated with cervical pain (1).
<ol>
 	<li>Mäkela, M., Heliövaara, M., Sievers, K., Impivaara, O., Knekt, P., &amp; Aromaa, A. (1991). Prevalence, determinants, and consequences of chronic neck pain in Finland. American journal of epidemiology, 134(11), 1356-1367.</li>
</ol>
</li>
</ul>

An anatomical direction; toward the tail, relative to humans this term is often used to refer to "in the direction of the tale (toward the feet)".

Example, to release the trapezius muscle the therapist used a force directed caudally.

Center of mass (CoM) - an object's mean position of mass; that is, a point that is perfectly surrounded by an equal amount mass in all directions.

Center of gravity (CoG) - point where gravity appears to act. Since the human body is so small compared to the earth, we can assume gravity acts uniformly on the body, and that CoG and CoM are the same.
<ul>
 	<li>Example, the CoM of the human body while lying down or standing straight up is close to our navel. However, it is possible that during a resistance exercise, the combination of the body's weight and the weight of the resistance will place the combined CoM outside the body. For example, during the mid-portion of a <a href="https://brentbrookbush.com/vimeo_videos/back-squat/" target="_blank" rel="noopener">back squat</a> the CoM would be several anterior to the naval.</li>
</ul>

An anatomical direction; toward the head (synonym: cranial)

Example, hip pain was felt with any force directed cephalad.

Cohort Study - a particular form of longitudinal study that samples a cohort (a group of people who share a defining characteristic), performing a cross-section at intervals through-out a period of time. A cohort study is a quasi-experimental design often used in medicine to aid in determining etiology or a cause-and-effect relationship. In this study type exposure is the independent variable and outcome is dependent.
<ul>
 	<li>Example, the study by Cholewicki et al. (1) investigated Yale Varsity Athletes (the cohort) with 2 and 3 year follow up (longitudinal design) and found that trunk muscle response time to off-loading was predictive of future low back injury.</li>
</ul>
<ol>
 	<li><a href="https://brentbrookbush.com/articles/research-corner/core/increased-trunk-muscle-latency-may-cause-rather-than-result-from-low-back-pain/" target="_blank" rel="noopener noreferrer">Cholewicki, J., Silfies, S., Shah, R., Greene, H., Reeves, N. Alvi, K., Goldberg, B. (2005). Delayed trunk muscle reflex responses increase the risk of low back injuries. Spine. 30(23), 2614-2620</a></li>
</ol>

Comparable Sign: A combination of pain, stiffness and/or spasm during examination that is comparable to the patients symptoms.
<ul>
 	<li>One common error made during evaluation with special tests is attention given to any discomfort or pain, rather than attempting to identify the pain/discomfort related to the patient's complaint (concordant/comparable sign). Many special tests purposefully test tissue limits and are at least mildly uncomfortable in every individual. Basing your assessment on positive tests that resulted in "concordant/comparable signs" will improve your chances of arriving at the correct diagnosis.</li>
</ul>

An alternative movement pattern that has been adopted to compensate for dysfunction/impairment in the human movement system.
Example: A lack of calf extensibility may limit dorsiflexion, leading to the knees bowing inward (functional valgus) and excessive forward lean of the torso during a squat.

An arthrokinematic motion - the approximation of joint surfaces; that is, a force that directs one bone surface into another resulting in a reduction in intra-articular volume. Although widely thought of as a "destructive force", it is likely best to consider compression as a naturally occurring, stabilizing force. Any arthrokinematic force in excess (spin, glide, roll, traction) may be viewed as potentially deleterious.

For example, during a squat the femoral head is compressed into the acetabulum by muscular forces, bodyweight and any additional external load.

Concave (Concavity) - Having an outline or surface curved like the interior surface of a bowl or sphere - to cave-in or curve inward.
<ul>
 	<li>Example, the internal surfaces of the pelvis is concave, holding some of the bodies viscera.</li>
</ul>

Concordant Sign - The patient's specific pain, symptom or complaint. 
<ul>
 	<li>One common error made during evaluation with special tests is attention given to any discomfort or pain, rather than attempting to identify the pain/discomfort related to the patient's complaint (concordant/comparable sign). Many special tests purposefully test tissue limits and are at least mildly uncomfortable in every individual. Basing your assessment on positive tests that resulted in "concordant/comparable signs" will improve your chances of arriving at the correct diagnosis.</li>
</ul>

Conductivity: Stimulation results in more than a local effect (1).
<ul>
 	<li>For example, in a muscle cell the stimulation of a motor endplate results in a change in cell membrane polarity that rapidly propagates (is conducted) along the entire length of the muscle cell, stimulating all sacromere.</li>
</ul>
<ol>
 	<li>Saladin, K. (2012). Anatomy &amp; Physiology: The unity of form and function. (6th ed.). New York: McGraw-Hill.</li>
</ol>

A condyloid joint (also called condylar, bicondylar, ellipsoid, or ellipsoidal) is an ovoid articular surface, or condyle, that is received into an elliptical cavity.  These joints permit movement in two planes.  Examples include the knee, metacarpophalangeal joints and metatarsophalangeal joints.

Connective Tissue Cell - One of the four basic types of animal tissue, consisting mostly fibers and ground substance.  These cells are specialized to binds organs together, holds them in place, protect them from external forces, and may fill space in the body's cavities.

Example, the body's muscles are enclosed in durable connective tissue sheets known as the "epimysium", "perimysium", and "endomysium," which and in support and transmitting force.
<ol>
 	<li>Saladin, K. (2014). Anatomy &amp; physiology: The unity of form and function. McGraw-Hill Higher Education, New York. ISBN: 9780073403717</li>
</ol>

Contractility: The ability to shorten (1).
<ul>
 	<li>Contractility: Muscle cells are unique in the amount they can shorten when stimulated; this is this largerly due to the highly organized and unique arrangement of myofilaments (actin and myosin).</li>
</ul>
<ol>
 	<li>Saladin, K. (2012). Anatomy &amp; Physiology: The unity of form and function. (6th ed.). New York: McGraw-Hill.</li>
</ol>

Pertaining to the opposite side

Example, the external oblique muscle performs contralateral rotation; rotation to the opposite side.

Convex (Convexity) - Having an outline or surface curved like the exterior of a circle or sphere - to bulge or curve outward.
<ul>
 	<li>Example, the top of your head is shaped by the convex exterior surface of your skull.</li>
</ul>

Correlational Research - Non-experimental <a href="https://www.questionpro.com/blog/what-is-research/">research</a> method in which the statistical relationship between two variables is investigated.
<ul>
 	<li>In this research by Kwon et al., a correlation was noted between a decrease in extensibility during a hamstring length test (goniometry) and current knee pain (1).</li>
</ul>
<ol>
 	<li><a href="https://brentbrookbush.com/articles/research-corner/knee/correlation-patellofemoral-pain-syndrome-pfps-hamstring-activity/" target="_blank" rel="noopener">Kwon O, Yun M, and Lee W. (2014). Correlation between intrinsic patellofemoral pain syndrome in young adults and lower extremity biomechanics. J. Phys. Ther. Sci. 26: 961-964</a></li>
</ol>

Counter-nutation - posterior rotation of sacrum relative to ilium, and/or anterior rotation of ilium relative to sacrum.
<ul>
 	<li>The pelvic floor muscles are examples of muscle that may counter-nutate the sacrum.</li>
</ul>
[caption id="attachment_126335" align="aligncenter" width="400"]<a href="https://brentbrookbush.com/wp-content/uploads/2018/10/Nutation.png"><img class=" wp-image-126335" src="https://brentbrookbush.com/wp-content/uploads/2018/10/Nutation.png" alt="Nutation and Counter-nutation of the Sacroiliac Joint" width="400" height="967" /></a> Nutation and Counter-nutation of the Sacroiliac Joint[/caption]

&nbsp;

Crossover (Study) Design - A type of longitudinal, repeated measures quasi-experimental design in which each group receives both treatments, but at different times. It is named "crossover" due to the patients "crossing-over" to the other treatment or sham group after a specified period of time.
<ul>
 	<li>This type of study has the advantage of every individual serving as their own control, which may reduce the influence of confounding variables.</li>
 	<li>Unfortunately, the design itself introduces the chances that anyone receiving the experimental variable in the first period will continue to be effected in the second period.</li>
</ul>
In a study by Senna et al., a cross-over design was used to investigate the difference load made on inter-set rest intervals (1).
<ol>
 	<li><a href="https://brentbrookbush.com/articles/research-corner/strength-training-research-corner/heavy-vs-light-load-single-joint-exercise-performance-with-different-rest-periods/" target="_blank" rel="noopener">Senna, G.W., Rodrigues, B.M., Sandy, Scudese, Bianco, A, &amp; Dantas, E.H.M. (2017). Heavy vs light load single-joint exercise performance with different intervals. Journal of Human Kinetics, 58, 197-206. </a></li>
</ol>

Cross-sectional Study - a research design that involves gathering data from a population or representative subset at a specific point in time.
<ul>
 	<li>Example, the study by Karimi-Mobarake et al.(1) investigated the prevalence of genu varum and genu valgum among school children 7-11 years old in Iran.</li>
</ul>
<ol>
 	<li><a href="https://brentbrookbush.com/articles/research-corner/knee/low-prevalence-of-genu-varum-and-valgum-among-elementary-school-children/" target="_blank" rel="noopener noreferrer">Karimi-Mobarake, M., Kashefipour, A., Yousfnejad, Z. The prevalence of genu varum and genu valgum in primary school children in Iran 2003-2004. (2005) Journal of Medical Science 5(1). 52-54</a></li>
</ol>

Cytokine - A broad and loose category of small proteins that act through receptors, and are especially important to immune function (inflammation).
<ul>
 	<li>Cytokines include substances such as interferon, interleukin, and growth factors, which are secreted by certain cells of the immune system and have an effect on other cells. Their definite distinction from hormones is a topic of continued research.</li>
</ul>
&nbsp;

Dependent variable - in research, this is the variable that is changed by the independent variable, most often this is the "outcome" of the study.
<ul>
 	<li>Example, in the study by Cleland et al. (1), the independent variable is "thoracic manipulation," and the dependent variable is "lower trapezius muscle strength."</li>
</ul>
<ol>
 	<li><a href="https://brentbrookbush.com/articles/research-corner/short-term-effects-lower-thoracic-manipulation-lower-trapezius-muscle-strength/" target="_blank" rel="noopener noreferrer">Cleland J, Selleck B, Stowell T, Brown L, Alberini S, St. Cyr H, Caron T. Short-term Effects of Thoracic Manipulation on Lower Trapezius Muscle Strength.  Journal of Manual &amp; Manipulative Therapy. 2004; 12(2): 82-90</a></li>
</ol>

An anatomical direction; further from the trunk or center of the body

Example, the foot is at the distal end of the leg.

An arthrokinematic motion - a force applied to a body part that may result in the separation of joint surfaces, a reduction in intra-articular pressure, and/or an increase in intra-articlar space.

For example, to hang from one's hands (i.g. in preparation for a pull-up) results in a traction force on the glenohumeral joint (shoulder).

An anatomical term of location; back or upper surface

Example, shoe laces may compress tissues on the dorsal surface of the foot

The "drawing-in" maneuver is a common cue used during exercise and rehabilitation programs. A light contraction of the <a href="https://brentbrookbush.com/articles/muscular-anatomy/transverse-abdominis/" target="_blank" rel="noopener">transverse abominis</a> (and potentially the entire <a href="https://brentbrookbush.com/articles/corrective-exercise-articles/core-subsystems/intrinsic-stabilization-subsystem/" target="_blank" rel="noopener">intrinsic stabilization subsystem</a>) achieved by gently pulling the lower abdominal region away from one's waist band. This should have minimal effect on breathing, and should not be confused with a maximal contraction of the <a href="https://brentbrookbush.com/articles/muscular-anatomy/transverse-abdominis/" target="_blank" rel="noopener">transverse abdominis</a> resulting in a "vacuum pose".
<ul>
 	<li>Research often refers to this maneuver as the "abdominal drawing-in maneuver"; abbreviated ADIM.</li>
</ul>
Development and introduction of this cue into practice is based on the pivotal research and resulting text:
<ol>
 	<li>Carolyn Richardson, Paul Hodges, Julie Hides. Therapeutic Exercise for Lumbo Pelvic Stabilization – A Motor Control Approach for the Treatment and Prevention of Low Back Pain: 2nd Edition (c) Elsevier Limited, 2004</li>
</ol>

Faulty or abnormal movement; an alteration of normal kinematics.

For example, joint stiffness or a reduction in arthrokinematics motion that results in limited osteokinematic range of motion - inadequate inferior glide of the femoral head resulting in limited abduction of the hip.

The seeping into, or abnormal collection of fluid in a body cavity.

For example, knee effusion describes swelling within the knee joint.

Note: the word "effusion" is used differently in medicine than it is used in reference to the movement (seeping out) of liquids and gases, for example in chemistry.

&nbsp;

A trait of body tissues that allows a tissue to return to its resting length or state after deformation or stretch.
Example:  Muscle is elastic tissue; many muscles will return to their resting length after being stretched to 150% of that length without any appreciable change in tissue quality.

Elasticity: Elasticity refers to the ability of a cell to return to its resting length after being stretched/lengthened.
<ul>
 	<li>Note: this term is often confused with extensibility. Elasticity is not the ability to stretch; it is the ability to return to normal length after being stretched. Muscle tissue, connective tissue and even nerve tissue have varying levels of elasticity.</li>
</ul>
<ol>
 	<li>Saladin, K. (2012). Anatomy &amp; Physiology: The unity of form and function. (6th ed.). New York: McGraw-Hill.</li>
</ol>

Epithelial cell - One of the four basic cell types, found lining the body's cavities, blood vessels, organs and constitutes most gland tissue.  These cells are specialized to aid with absorption, secretion, or act as a barrier from foreign objects.
<ol>
 	<li>Saladin, K. S., &amp; Miller, L. (1998). Anatomy &amp; physiology. New York (NY): WCB/McGraw-Hill.</li>
</ol>

Equilibrium - a state in which opposing forces or influences are balanced.
<ul>
 	<li>For example, to maintain a neutral trunk while pushing or pulling a weight in one hand, your core musculature must balance the force by creating an equal amount of force in the opposite direction.</li>
</ul>

The study of causation, or origination. The word is commonly used in the medical professions, where it may refer to the study of why things occur, or the reason behind why things act a certain way.

For example, the etiology of low back pain is a complex subject, with multiple contributing factors and various structures implicated.

<div class="gs_citr" tabindex="0">Evidence-based medicine (practice) is the integration of best research evidence with clinical expertise and patient(client) values (2)."</div>
<ul>
 	<li class="gs_citr" tabindex="0">...the conscientious, explicit and judicious use of current best evidence in making decisions about the care of individual patients (clients).  It involves the integration of at least (a) clinical expertise/expert opinion, (b) external scientific evidence, and (c) client/patient/caregiver perspectives to provide high-quality services reflecting the interests, values, needs, and choices of the individuals we serve (1).</li>
</ul>
&nbsp;
<ol>
 	<li id="gs_cit1" class="gs_citr" tabindex="0">Sackett, D. L., Rosenberg, W. M., Gray, J. M., Haynes, R. B., &amp; Richardson, W. S. (1996). Evidence based medicine: what it is and what it isn't. Bmj, 312(7023), 71-72.</li>
 	<li class="gs_citr" tabindex="0">Sackett D et al. Evidence-Based Medicine: How to Practice and Teach EBM, 2nd edition. Churchill Livingstone, Edinburgh, 2000, p.1</li>
</ol>

Excitability: The ability of a cell to change in membrane conductance as a response to stimulation.

<ul>
 	<li>For example, muscle cells are specialized to react to a change in membrane potential with contraction, where as nerve cells are specialized to propagate a change in membrane potential along there axons and communicate that message to other tissues via neurotransmitters.
</li>
</ul>
<ol>
 	<li>Saladin, K. (2012). Anatomy &amp; Physiology: The unity of form and function. (6th ed.). New York: McGraw-Hill.</li>
</ol>

Excitation threshold: The level that a depolarization must reach for an action potential to occur.
<ul>
 	<li>The excitation threshold is a contributing factor to the "all-or-none" response of muscle and nerves cells to a stimulus.</li>
</ul>

Exercise Progression - Modification of an exercise with the intent of promoting adaptation by increasing demand. This can be accomplished by increasing reps, load, tempo, range of motion, complexity, and/or challenge to an individual's stability.
<ul>
 	<li>Because load, reps, tempo and complexity are often explicitly noted, the term "exercise progression" is most often used throughout Brookbush Institute (BI) content to refer to an exercise, or series of exercises that make it harder to maintain stability with good form.
<ul>
 	<li>Sample Exercise Progression: <a href="https://brentbrookbush.com/vimeo_videos/kneeling-chop-pattern/" target="_blank" rel="noopener">Kneeling Chop</a> to <a href="https://brentbrookbush.com/vimeo_videos/static-standing-chop-pattern/" target="_blank" rel="noopener">Standing Chop</a> to <a href="https://brentbrookbush.com/vimeo_videos/single-leg-chop-pattern/" target="_blank" rel="noopener">Single-leg Chop</a></li>
</ul>
</li>
</ul>

Exercise regression - The opposite of progression; that is, modification of an exercise with the intent of reducing demand. This can be accomplished by decreasing reps, load, tempo, range of motion, complexity, and/or challenge to an individual's stability. Generally, regressions are used to modify an exercise to the client's current level of ability, with the intent of improving form, motor learning and retention.
<ul>
 	<li>Because load, reps, tempo and complexity are often explicitly noted, the term "exercise regression" is most often used throughout Brookbush Institute (BI) content to refer to an exercise or series of exercises that make it easier to maintain stability with good form.
<ul>
 	<li>Sample Exercise Regression: <a href="https://brentbrookbush.com/vimeo_videos/single-leg-chop-pattern/" target="_blank" rel="noopener">Single-leg Chop</a> to <a href="https://brentbrookbush.com/vimeo_videos/static-standing-chop-pattern/" target="_blank" rel="noopener">Standing Chop</a> to <a href="https://brentbrookbush.com/vimeo_videos/kneeling-chop-pattern/" target="_blank" rel="noopener">Kneeling Chop</a></li>
</ul>
</li>
</ul>

Experimental Research - Studies in which the researchers introduce the variable to be studied, with the intent of observing the outcome. This is different than observational research which observes the effect of a variable already present. Many texts also assert that experimental research should include randomization and ideally a control group, as is seen in Randomized Control Trials. Studies in which the variable is introduced by the researchers, but participants are not randomized may be considered Quasi-experimental research.
<ul>
 	<li>In this study by Esformes, the experimental variable was squat depth and the outcome measures observed were various performance measures related to power (1).</li>
</ul>
<ol>
 	<li><a href="https://brookbushinstitute.com/article/back-squat-depth-lower-body-post-activation-potentiation/" target="_blank" rel="noopener">Esformes, J., &amp; Bampouras, T. (2013). Effect of back squat depth on lower-body postactivation potentiation. Journal of Strength and Conditioning Research, 27(11), 2997-3000.</a></li>
</ol>
&nbsp;

Extensibility: The ability of a cell to be stretched or lengthened without damage (1).
<ul>
 	<li>For example, most cells would rupture with even a modest stretch, but muscles can stretch up to 3 times their contracted length.</li>
</ul>
<ol>
 	<li>Saladin, K. (2012). Anatomy &amp; Physiology: The unity of form and function. (6th ed.). New York: McGraw-Hill.</li>
</ol>

False Negative - the proportion of negatives in a group that were assessed incorrectly (assessed as negative when the patient was actually positive)
<ul>
 	<li>Test Results: Although most tests/assessments result in either a positive or negative, the accuracy of a test is dependent on the number  of positives and negatives that are correct. Therefore, when the accuracy of a test is determined, their are 4 possible results, because a positive or negative result could be right (true) or wrong (false).</li>
</ul>

False Positive - the proportion of positives in a group that were assessed incorrectly (assessed as positive when the patient was actually negative)
<ul>
 	<li>Test Results: Although most tests/assessments result in either a positive or negative, the accuracy of a test is dependent on the number  of positives and negatives that are correct. Therefore, when the accuracy of a test is determined, their are 4 possible results, because a positive or negative result could be right (true) or wrong (false).</li>
</ul>

The function of fascia is to transmit force, provide support, and protect tissues. Fascia can effect motion by:
Transmitting force from one or more muscles (example: the thoracolumbar fascia)
Restricting motion in cases of adaptive shortening and/or adhesion to proximal structures (example: iliotibial band in cases of lower-leg dysfunction)
Elastic recoil after stretching can contribute to force production (example: plyometric exercise)

Note: There is evidence that fascia may house more receptors related to human movement than other tissues. In this way fascia may act as a motherboard for the nervous system

The fascial system does not contract or develop trigger points, and its capacity to adapt to stretching and or strengthening exercise is limited, especially when compared to the adaptive capacity of muscle tissue.

Fibromyalgia - A loosely defined diagnosis that is associated with a combination of widespread pain in combination with 2) tenderness at 11 or more of the 18 specific tender point sites. Consideration may also be given to the presence of psychosocial stressors and inflammatory disease in the patients history. Newer research suggests that fibromyalgia may be at least in part due to central sensitization of myofascial pain, often associated with trigger points (1 - 4).
<ol>
 	<li>Wolfe, F. (2018). Fibromyalgia Syndrome and Fibromyalgia Syndrome Criteria: Problems in Definition and Validity. Fibromyalgia Syndrome and Widespread Pain: From Construction to Relevant Recognition.</li>
 	<li>Wolfe, F., Smythe, H. A., Yunus, M. B., Bennett, R. M., Bombardier, C., Goldenberg, D. L., ... &amp; Fam, A. G. (1990). The American College of Rheumatology 1990 criteria for the classification of fibromyalgia. Arthritis &amp; Rheumatism: Official Journal of the American College of Rheumatology, 33(2), 160-172.</li>
 	<li>Alonso-Blanco, C., Fernandez-de-las-Penas, C., Morales-Cabezas, M., Zarco-Moreno, P., Ge, H. Y., &amp; Florez-García, M. (2011). Multiple active myofascial trigger points reproduce the overall spontaneous pain pattern in women with fibromyalgia and are related to widespread mechanical hypersensitivity. The Clinical journal of pain, 27(5), 405-413.</li>
 	<li>Staud, R., Nagel, S., Robinson, M. E., &amp; Price, D. D. (2009). Enhanced central pain processing of fibromyalgia patients is maintained by muscle afferent input: a randomized, double-blind, placebo-controlled study. PAIN®, 145(1-2), 96-104.</li>
</ol>
&nbsp;

Muscles that act to reduce or prevent movement at proximal joints to improve force transmission.
Example: The muscles of the core are important fixators; reducing motion of the spine/trunk to enhance force transmission between the extremities and environment.

An increase in joint stability via compressive forces resulting from muscular contraction and increased tension in fascial structures (1,2).
<ul>
 	<li>This term is most often used in reference to core intrinsic stabilizers, the thoracolumbar fascia and the sacroiliac joint; however, force closure and form closure have been mentioned in the literature referring to other joints.</li>
 	<li>Related term: Form closure</li>
</ul>
<ol>
 	<li>Andry Vleeming, Vert Mooney, Rob Stoeckart. Movement, Stability &amp; Lumbopelvic Pain: <a class="glossaryLink " title="Glossary: Integration" href="https://brentbrookbush.com/glossary/integration/" target="_blank" rel="noopener noreferrer" data-cmtooltip="&lt;div class=glossaryItemTitle&gt;Integration&lt;/div&gt;&lt;div class=glossaryItemBody&gt;Making a whole of parts.&lt;br /&gt;&lt;br /&gt;Example, The Brookbush Institute uses an integrative approach to explaining and addressing human movement.&lt;/div&gt;">Integration</a> of Research and Therapy. (c) 2007 Elsevier Limited</li>
 	<li id="gs_cit1" class="gs_citr" tabindex="0">Vleeming, A., Pool-Goudzwaard, A. L., Stoeckart, R., van Wingerden, J. P., &amp; Snijders, C. J. (1995). The Posterior Layer of the Thoracolumbar Fascia| Its Function in Load Transfer From Spine to Legs. Spine, 20(7), 753-758.</li>
</ol>

The relative contribution of joint shape and structure to the stability of a joint (1,2).
<ul>
 	<li>This term is most often used in reference to the "rough" articulating surfaces of the sacroiliac joint and the wedge shape of the sacrum; however, force closure and form closure have been mentioned in the literature referring to other joints.</li>
 	<li>Related term: Force closure</li>
</ul>
<ol>
 	<li>Andry Vleeming, Vert Mooney, Rob Stoeckart. Movement, Stability &amp; Lumbopelvic Pain: <a class="glossaryLink " title="Glossary: Integration" href="https://brentbrookbush.com/glossary/integration/" target="_blank" rel="noopener noreferrer" data-cmtooltip="&lt;div class=glossaryItemTitle&gt;Integration&lt;/div&gt;&lt;div class=glossaryItemBody&gt;Making a whole of parts.&lt;br /&gt;&lt;br /&gt;Example, The Brookbush Institute uses an integrative approach to explaining and addressing human movement.&lt;/div&gt;">Integration</a> of Research and Therapy. (c) 2007 Elsevier Limited</li>
 	<li id="gs_cit1" class="gs_citr" tabindex="0">Vleeming, A., Pool-Goudzwaard, A. L., Stoeckart, R., van Wingerden, J. P., &amp; Snijders, C. J. (1995). The Posterior Layer of the Thoracolumbar Fascia| Its Function in Load Transfer From Spine to Legs. Spine, 20(7), 753-758.</li>
</ol>

An arthrokinematic motion - linear motion across a joint surface parallel to the plane of the adjacent joint surface, just as your posterior moves relative to a "slide" in a park.

For example, the glide of facet joint in the spine during spinal flexion and extension, or the posterior glide of the humeral head that must accompany anterior roll to maintain congruence with glenoid fossa during shoulder horizontal adduction.

A plane joint (also called an arthrodial joint, gliding joint or plane articulation) is a synovial joint which allows only gliding movement in the plane of the articular surfaces. The opposed surfaces of the bones are flat or almost flat, with movement generally limited by tight capsules and ligaments. Plane joints are numerous, are most often small, and allow very little motion.  Examples include the carpal joints of the wrist, the tarsal joints of the ankle, and the facet joints of the spine.

"...refers to the measurement of angles, in particular the measurement of angles created at human joints by the bones of the body (1).

&nbsp;
<ol>
 	<li>Cynthia C. Norkin, D. Joyce White. Measurement of Joint Motion: A Guide to Goniometry 3rd Edition. Copyright (C) 2003 by F.A. Davis Company</li>
</ol>

Ground reaction force (GRF) - The force exerted by the ground on the body in contact with it.

For example, when a runner's foot strikes the ground with a force equal to the mass of the individual times their acceleration due to gravity, momentum and muscular exertion, the ground exerts an equal and opposite force on the runner's foot.
<ul>
 	<li>GRF is often measured in research studies using force plates as a means of quantitatively measuring the force generated by an individual.</li>
</ul>

H-Band - Refers to the central zone of a sarcomere that looks lighter under a microscope.  This area of the sarcomere is a lighter portion of the A-band where there is no overlap between the thinner filaments (actin), and the thicker filaments (myosin).
<ul>
 	<li>Example, when a muscle contracts, actin and myosin cross-bridging occurs in the region of the A-band until the H-band is reached where no overlap occurs.</li>
</ul>
<ol>
 	<li>Saladin, K. (2014). Anatomy &amp; physiology: The unity of form and function. McGraw-Hill Higher Education, New York. ISBN: 9780073403717</li>
</ol>

A hinge joint (also called a ginglymus) is a synovial joint in which the articular surfaces fit one another in a way that only permits motion in one plane. Examples include the elbow, the knee (unless considered a condyloid joint) and the interphalangeal joints.

Holism (holistic) (biological holism) - (from Greek holos "all, whole, entire") is the idea that systems and their properties should be viewed as wholes, not just as a collection of parts.
<ul>
 	<li>Summarized by Aristotle in his "Metaphysics": "The whole is more than the sum of its parts". However, the term "holism" was introduced into language by the South African statesman Jan Smuts as recently as 1926. (Smuts J. C. 1987 [1926]. Holism and evolution. Cape Town: N &amp; S Press.)</li>
</ul>
Example: The Brookbush Institute promotes a holistic approach to human movement science, in which the muscular, fascial, articular and neural systems are not viewed as separable and all proximal segments are considered.

Hormone: Chemical messengers produced by the endocrine system, transported via tissue fluids such as blood, to stimulate cells to "act."
<ul>
 	<li>Example: Growth hormone is secreted by the pituitary gland in the brain; stimulating growth, cell reproduction and cell regeneration in certain types of cells</li>
</ul>
The English physician E. H. Starling discovered in collaboration with the physiologist W. M. Bayliss secretin, the first hormone, in 1902. (1).
<ol>
 	<li>Henriksen, J. H., &amp; de Muckadell, O. S. (2000). Secretin, its discovery, and the introduction of the hormone concept. Scandinavian journal of clinical and laboratory investigation, 60(6), 463-472.</li>
</ol>

A range of motion achieved by the patient/client that is more than normal.
<ul>
 	<li>Note: Both hyper-mobility and hypo-mobility may adversely affect motion and may lead to deleterious effects on joints and soft tissue over time. There is no evidence to suggest that more or less flexibility than normal is beneficial.</li>
</ul>
Example: If an individual can place their forehead on their knees they are likely hypermobile at one, if not several joints

Example 2: 110° of shoulder external rotation would be considered hyper-mobile.

Hyperplasia is an increase in organic tissue size due to an adaptive increase in the number of cells per organ.
<ul>
 	<li>Although muscle hyperplasia has been noted in some animals, human muscle tissue does not seem to have this adaptive ability.</li>
</ul>

A condition of excessive tone of the skeletal muscles; increased resistance of muscle to passive stretching.  May be related to increased neural drive, synergistic dominance, trigger points, reflexive over-activity, and/or muscle length.
Example:  Individuals who exhibit ankle eversion and abduction during an overhead squat assessment likely have hypertonic fibularis (peroneal) muscles.

Muscular hypertrophy is an increase in muscle mass/size due to increase in the volume and cross-sectional area (CSA) of individual muscle cells. The increase in cross-sectional area can be attributed to an an increase in contractile proteins and structural elements (myofibrillar hypertophy), as well as an increase in glycogen storage and elements related to metabolism (sarcoplasmic hypertophy). Hypertrophy is an adaptation of both cardiac and skeletal muscle fibers in response to progressive increases in workload.
<ul>
 	<li>Note: Hypertrophy is not hyperplasia. Hyperplasia is an increase in muscle size due to an adaptive increase in the number of muscle fibers/cells per muscle. This type of adaptation does not occur in human muscle tissue.</li>
</ul>

A range of motion achieved by a patient/client that is less than normal.
<ul>
 	<li>Note: Both hyper-mobility and hypo-mobility may adversely affect motion and may lead to deleterious effects on joints and soft tissue over time. There is no evidence to suggest that more or less flexibility than normal is beneficial.</li>
</ul>
Example: If the end range of shoulder external rotation is reached and measured as 75° during goniometric assessment, the client/patient is exhibiting hypomobility of the glenohumeral joint (shoulder).

Hypothesis - a proposed explanation for a phenomenon; "scientific hypotheses" are generally constructed in a way that is testable or falsifiable.
<ul>
 	<li>Example: The hypothesis, "excessive knee valgus may be correlated with future knee pain and injury," has been the subject of several studies published over the last decade.</li>
</ul>

Diminished tone of skeletal muscles; diminished resistance of muscles to passive stretching.   May be related to inhibition, reciprocal inhibition, arthrokinematics inhibition and/or  increased resting length of muscle.
Example:  If your knees cave (hip adduction) during a squat or leg-press it is likely that your gluteus medius is hypotonic.

I-Band - Refers to the part of the muscle cell that looks lighter under a microscope.  This area of the cell is lighter due to parallel arrangement of thinner filaments (actin), and no overlap with the thicker filaments (myosin).
<ul>
 	<li>As a muscle contracts, the I-bands will decrease in width and move closer to one another.</li>
</ul>
<ol>
 	<li>Saladin, K. (2014). Anatomy &amp; physiology: The unity of form and function. McGraw-Hill Higher Education, New York. ISBN: 9780073403717</li>
</ol>

Independent variable - in research, this is the variable or phenomenon being manipulated in the study.
<ul>
 	<li>Example, in the study by Ghanbari et al. (1), the independent variable is "knee joint mobilization", the dependent variable is "quadriceps muscle strength."</li>
</ul>
<ol>
 	<li><a href="https://brentbrookbush.com/articles/research-corner/effect-knee-joint-mobilization-quadriceps-muscle-strength/" target="_blank" rel="noopener noreferrer">Ghanbari A. and Kamalgharibi S. (2013). Effect of knee joint mobilization on quadriceps muscle strength. International Journal of Health and Rehabilitation Sciences. 2(4): 186-191</a></li>
</ol>

An anatomical direction; toward the bottom (below)

Example, the mouth is inferior to the eyes

A reduction in neural drive, muscular activity, and or force output due to altered neuromuscular reflex.  Alterations in neuromuscular reflex may occur due to increases in muscle length (hypothesis: increased excitation threshold), altered reciprocal inhibition in response to increased antagonist tone, and or alterations in joint motion (arthrokinematics inhibition).

Making a whole of parts.

Example, The Brookbush Institute uses an integrative approach to explaining and addressing human movement.

Intermuscular Coordination - Optimal timing and motor unit recruitment of agonists, antagonists, synergists, neutralizers, stabilizers and fixators.

Example: Role of Muscles during Hip Extension
<ul>
 	<li><a class="glossaryLink " style="box-sizing: border-box; font-family: roboto; color: #000000 !important; font-size: 15px; outline: none; background: transparent; border-bottom: 1px dotted #000000 !important; text-decoration: none;" title="Glossary: Prime Mover" href="https://brentbrookbush.com/glossary/prime-mover/" target="_blank" rel="noopener" data-cmtooltip="&lt;div class=glossaryItemTitle&gt;Prime Mover&lt;/div&gt;The muscle most responsible for a joint action under load -&lt;br /&gt;&lt;br /&gt;That is, the muscle that can produce the most force for a given joint action. Often this term is used synonymously with the term agonist. The prime mover as defined above, may or may not be the most active muscle for a joint action during activities of daily living.&lt;br /&gt;&lt;br /&gt;Example: the gluteus maximus is the most powerful hip extensor and therefore the prime mover; however, the hamstrings are likely the most active hip extensors during low level activities like walking or standing.">Prime Mover</a>:  <a href="https://player.vimeo.com/external/82855344.hd.mp4?s=54c3e7d98fb9d4e0af8d282c85ba9b3e">Gluteus maximus</a></li>
 	<li><a class="glossaryLink " style="box-sizing: border-box; font-family: roboto; color: #000000 !important; font-size: 15px; outline: none; background: transparent; border-bottom: 1px dotted #000000 !important; text-decoration: none;" title="Glossary: Synergists" href="https://brentbrookbush.com/glossary/synergists/" target="_blank" rel="noopener" data-cmtooltip="&lt;div class=glossaryItemTitle&gt;Synergists&lt;/div&gt;Muscles that assist the prime mover in performing a joint action.&lt;br /&gt;&lt;br /&gt;That is, all muscles that can perform a joint action that are not the prime mover, are termed synergists.&lt;br /&gt;Example: The rectus abdominis is the prime mover of spinal flexion. All other muscles that can perform spinal flexion are synergists including – external obliques, internal obliques and psoas.">Synergists</a>: <a href="https://brentbrookbush.com/articles/muscular-anatomy/biceps-femoris/">Biceps femoris (long head)</a>, <a href="https://brentbrookbush.com/articles/muscular-anatomy/semitendinosus-and-semimembranosus/">semitendinosus, semimembranosus</a>, <a href="https://brentbrookbush.com/articles/muscular-anatomy/adductors/">posterior head of adductor magnus</a></li>
 	<li><a class="glossaryLink " style="box-sizing: border-box; font-family: roboto; color: #000000 !important; font-size: 15px; outline: none; background: transparent; border-bottom: 1px dotted #000000 !important; text-decoration: none;" title="Glossary: Antagonist" href="https://brentbrookbush.com/glossary/antagonists/" target="_blank" rel="noopener" data-cmtooltip="&lt;div class=glossaryItemTitle&gt;Antagonist&lt;/div&gt;Muscles that oppose the prime mover and synergists for a given joint action.&lt;br /&gt;&lt;br /&gt;That is, all the muscles that can perform the opposing joint action.&lt;br /&gt;&lt;br /&gt;Example: The triceps and anconeus are antagonists during elbow flexion.">Antagonists</a>: <a href="https://brentbrookbush.com/articles/muscular-anatomy/psoas/">Psoas</a>, <a href="https://brentbrookbush.com/articles/muscular-anatomy/iliacus/">iliacus</a>, <a href="https://brentbrookbush.com/articles/muscular-anatomy/tensor-fascia-latae-tfl/">tensor fascia latae</a> (TFL),<a href="https://brentbrookbush.com/articles/muscular-anatomy/rectus-femoris/"> rectus femoris</a>, <a href="https://brentbrookbush.com/articles/muscular-anatomy/adductors/">anterior adductors (especially pectineus)</a>, <a href="https://brentbrookbush.com/articles/muscular-anatomy/sartorius/">sartorius</a></li>
 	<li><a class="glossaryLink " style="box-sizing: border-box; font-family: roboto; color: #000000 !important; font-size: 15px; outline: none; background: transparent; border-bottom: 1px dotted #000000 !important; text-decoration: none;" title="Glossary: Neutralizer" href="https://brentbrookbush.com/glossary/neutralizers/" target="_blank" rel="noopener" data-cmtooltip="&lt;div class=glossaryItemTitle&gt;Neutralizer&lt;/div&gt;Muscles that oppose unwanted joint motions created by the prime mover and/or synergists, and/or muscles that prevent unwanted ancillary motion.&lt;br /&gt;Example: The teres minor and infraspinatus neutralize the internal rotation force created by the pectoralis major during horizontal adduction of the shoulder.">Neutralizers</a>: <a href="https://brentbrookbush.com/articles/muscular-anatomy/gluteus-minimus/">Gluteus minimus</a> and <a href="https://brentbrookbush.com/articles/muscular-anatomy/gluteus-medius/">anterior fibers of gluteus medius</a> neutralize external rotation force of <a href="https://brentbrookbush.com/articles/muscular-anatomy/gluteus-maximus/">gluteus maximus</a></li>
 	<li><a class="glossaryLink " style="box-sizing: border-box; font-family: roboto; color: #000000 !important; font-size: 15px; outline: none; background: transparent; border-bottom: 1px dotted #000000 !important; text-decoration: none;" title="Glossary: Stabilizer" href="https://brentbrookbush.com/glossary/stabilizers/" target="_blank" rel="noopener" data-cmtooltip="&lt;div class=glossaryItemTitle&gt;Stabilizer&lt;/div&gt;Muscles whose primary role is to improve arthrokinematics by maintaining optimal alignment of joint surfaces.&lt;br /&gt;&lt;br /&gt;Most often these muscles are the most intrinsic muscles of a joint, have a larger percentage of Type I muscle fibers and are rich in proprioceptors.&lt;br /&gt;Example: The muscles of the rotator cuff act as stabilizers for most shoulder motions.">Stabilizers</a>: <a href="https://brentbrookbush.com/articles/muscular-anatomy/deep-rotators-of-the-hip/">Deep rotators of hip</a></li>
 	<li><a class="glossaryLink " style="box-sizing: border-box; font-family: roboto; color: #000000 !important; font-size: 15px; outline: none; background: transparent; border-bottom: 1px dotted #000000 !important; text-decoration: none;" title="Glossary: Fixator" href="https://brentbrookbush.com/glossary/fixators/" target="_blank" rel="noopener" data-cmtooltip="&lt;div class=glossaryItemTitle&gt;Fixator&lt;/div&gt;Muscles that act to reduce or prevent movement at proximal joints to improve force transmission.&lt;br /&gt;Example: The muscles of the core are important fixators; reducing motion of the spine/trunk to enhance force transmission between the extremities and environment.">Fixators</a>: <a href="https://brentbrookbush.com/articles/core-subsystems/intrinsic-stabilization-subsystem/">Intrinsic stabilization subsystem</a>, <a href="https://brentbrookbush.com/articles/muscular-anatomy/rectus-abdominis/">rectus abdominis</a>, <a href="https://brentbrookbush.com/articles/muscular-anatomy/internal-obliques/">internal</a> and <a href="https://brentbrookbush.com/articles/muscular-anatomy/external-obliques/">external obliques</a>, <a href="https://brentbrookbush.com/articles/muscular-anatomy/quadratus-lumborum/">quadratus lumborum</a>, <a href="https://brentbrookbush.com/articles/muscular-anatomy/erector-spinae/">erector spinae</a></li>
</ul>
&nbsp;

Example from: <a href="https://brentbrookbush.com/articles/anatomy-articles/introduction-to-functional-anatomy/kinesiology-of-the-hip/" target="_blank" rel="noopener">Introduction to Functional Anatomy: Kinesiology of the Hip</a>

Intramuscular coordination refers to the coordinated recruitment of motor units within a single muscle. This concept is used to explain increases in maximal strength and power; however, the coordinated and sequential recruitment of motor units is also essential to strength endurance and smooth coordinated motion.  Related terminology may include; motor unit recruitment, preferential recruitment, rate coding, sequence, etc..

Example: It is hypothesized that the "shaking" noted during a novice exercisers attempt at an activity like the <a href="https://brentbrookbush.com/vimeo_videos/ball-crunch-and-progressions/" target="_blank">stability ball crunch</a> may be due to relatively poor intramuscular coordination. Rather than smooth, sequential firing of rectus abdominis motor units, groups of motor units turn on and off in an uncoordinated manner.

Pertaining to the same side

Example, the quadratus lumborum performs ipsilateral flexion; lateral flexion toward the same side as the muscle.

An isoform, or variant, is a member of a set of similar proteins, that originate from the same gene, or gene family.
<ul>
 	<li>Example, the variations in myosin heavy chain proteins (MHC I, MHC IIA, MHC IIB/X) that contribute to the characteristic differences between muscle fiber types.</li>
</ul>

“The Prime Assumption”
Everything crossing a joint will influence joint motion during every joint action.

A concept that has expanded over the past several decades to describe the integration of 4 body systems (muscle, joints, fascia and nerves), as well as, the coordinated function of various body segments (e.g. hip, knee and ankle) to produce motion. Kinetic referring to motion, and chain being an analogy for the interdependent link between systems.

Example, the posterior kinetic chain, refers to the integrated function of nerves, muscles, fascia and joints on the posterior side of the body.

The concept of the kinetic chain was originally adapted from the work of a mechanical engineer named Franz Reuleaux (Kinematics of Machinery (1875)) by Dr. Arthur Steindler in 1955 (Steindler A: Kinesiology of the Human Body. Springfield, IL, Charles C. Thomas Co.. 1955).

Latent Trigger Point - A myofascial trigger point that is not painful at rest, only painful when palpated, and may or may not exhibit a characteristic referral pain pattern when palpated.  Latent trigger points do result in an acute point of sensitivity, in a taut band of muscle, and may restrict range of motion (1).

Note: Based on the clinical experience, the Brookbush Institute suggests that latent trigger points (sometimes refereed to as Tender Points) are more common than active trigger points. Further, they are likely addressed more often than trigger points; being the intended target of many soft-tissue mobility techniques.
<ol>
 	<li>David G. Simons, Janet Travell, Lois S. Simons, Travell &amp; Simmons’ Myofascial Pain and Dysfunction, The Trigger Point Manual, Volume 1. Upper Half of Body: Second Edition,© 1999 Williams and Wilkens</li>
</ol>

An anatomical direction; further from the midline

Example, the anterior deltoid is lateral to the pectoralis major

Length/Tension Relationship - The amount of force generated by a muscle is dependent on sarcomere length.
<ul>
 	<li>The ability of sarcomere to maximally produce force occurs when sarcomere length results in optimal overlap between actin and myosin. Stretching a sarcomere decreases overlap between actin and myosin filaments and reduces force production (1-3). When length is less than optimal, actin from opposite ends overlap and interfere with cross-bridging, and myosin filament are compressed as they contact the the Z-disk also reducing force (4)</li>
</ul>
<ol>
 	<li>Gordon, A. M., Huxley, A. F., &amp; Julian, F. J. (1966). The variation in isometric tension with sarcomere length in vertebrate muscle fibres. The Journal of physiology, 184(1), 170-192.</li>
 	<li>Edman, K. A. P. (1966). The relation between sarcomere length and active tension in isolated semitendinosus fibres of the frog. The Journal of Physiology, 183(2), 407-417.</li>
 	<li>Lieber, R. L., Loren, G. J., &amp; Friden, J. (1994). In vivo measurement of human wrist extensor muscle sarcomere length changes. Journal of neurophysiology, 71(3), 874-881.</li>
 	<li>Lieber, R. L. (2002). Skeletal muscle structure, function, and plasticity. Lippincott Williams &amp; Wilkins.</li>
</ol>
&nbsp;

Levels of Evidence - Relative to evidence-based practice, levels of evidence are an attempt to describe the strength of the results measured in a clinical trial or research study.  Note: levels of evidence do not supersede the critical evaluation of an experienced professional, and should be viewed as guidelines - a meta-analysis may be poorly constructed (Level IA), and a comparative study (Level III) may employ new technologies and a strong methodology.


The Levels of Evidence used by the Brookbush Institute, as described by Shekelle et al.(1):
<ul>
 	<li class="p1">IA - Evidence from meta-analysis of randomized controlled trials</li>
 	<li class="p1">IB - Evidence from at least one randomized controlled trial</li>
 	<li class="p1">IIA - Evidence from at least one controlled study without randomization</li>
 	<li class="p1">IIB - Evidence from at least one other type of quasi-experimental study</li>
 	<li class="p1">III - Evidence from non-experimental descriptive studies, such as comparative studies, correlation studies, and case-control studies</li>
 	<li class="p1">IV - Evidence from expert committee reports or opinions or clinical experience of respected authorities, or both</li>
</ul>
<ol>
 	<li>Shekelle, P. G., Woolf, S. H., Eccles, M., &amp; Grimshaw, J. (1999). Developing clinical guidelines. Western Journal of Medicine, 170(6), 348.</li>
</ol>

Likelihood Ratios - Likilihood ratios are used for assessing the value of performing a diagnostic test. They use sensitivity and specificity to determine whether a test result usefully changes the practitioner's chance (probability) of reaching the correct assessment. Calculation of likelihood ratios is based on Baye's theorem.
<ul>
 	<li>Positive Likelihood Ratio (LR+) - The ratio of a positive test result in people with the pathology to a positive test result in people without the pathology.</li>
 	<li>Negative Likelihood Ratio (LR-) - The ratio of a negative test result in people with the pathology to a negative test result in people without the pathology.</li>
</ul>

Longitudinal Study - a research design that involves observing the same variables, several times over a period of time.
<ul>
 	<li>Example, the study by Hewett et al. (1) is a type of longitudinal study called a "cohort study." This study investigated whether excessive knee valgus during landing was a predictor of knee injury risk in adolescent females over the course of a season.</li>
</ul>
<ol>
 	<li><a href="https://brentbrookbush.com/articles/research-corner/knee/research-review-increased-valgus-during-landing-predicts-acl-injury-in-adolescent-female-athletes/" target="_blank" rel="noopener noreferrer">Hewett, T. E., Myer, G. D., Ford, K. R., Heidt, R. S., Colosimo, A. J., McLean, S. G., &amp; Succop, P. (2005). Biomechanical measures of neuromuscular control and valgus loading of the knee predict anterior cruciate ligament injury risk in female athletes A prospective study. The American journal of sports medicine, 33(4), 492-501</a></li>
</ol>

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