Position Statement, Definitions, and Practical Application

Combined Aerobic and Strength Exercise

Blood Glucose and Lipid Profiles

Metaboloic Markers

Immune Function (and Probiotics)

Growth Hormones

Comparing Gender and Load

Comparing and Combining Circuit Resistance Training and Aerobic Training

Excess Post-exercise Oxygen Consumption (EPOC)

Body Image

No Change in Body Composition

Circuit Training 1-Page (Quick) Research Summary

Changes in Body Composition

Recommondations for Optimizing Body Composition Change

Circuit Training compared to Aerobic Training for Body Composition Change

Basketball

Soccer

Handball

Volleyball and Tennis

Mixed Sports

Occupation

Young Children (9-13 years old)

Comparing Circuit Training to Cardiovascular Exercise

Compared to Controls

Compared to Other Types of Training

Comparing Aerobic and Circuit Training

Normoxic or Hypoxic

Increases in Volume

Load Over Volume

Exceptions to Load Over Volume

Micro Sessions (6 - 14 min sessions)

Comparing Functional Training and Conventional Exercise Selection

Comparing Unstable Environments/Loads and Conventional Exercise Selection

Physiology, Caloric Expenditure, and Body Composition

Comparing Circuit Training and Physically Demanding Occupations (Fire-fighting and Fight Sports)

Comparing Hydraulic/Isokinetic Equipment and Conventional Exercise Selection

Comparing Strength and Power Exercises

Endurance Athletes

Sprinters

Specificity

Circuit Training (Vertical Loading) compared to Conventional Strength Training (Horizontal Loading)

Single Session Comparison

Outcomes Following Training Routines (6+ weeks)

VO2 Max

Circuit Training and Performance

Body Composition and Calories

Exercise Order

Additional Studies

Comparing Routines and Acute Variables (and Additional Studies)

Circuit Training Alone Improve Cardiovascular Performance

Circuit Training Compared to Higher Intensity Aerobic Exercise

Circuit Training Compared to Aerobic Exercise: Work-matched Routines

Acute Variables: Circuit Training

NASM

PACE

TPTA

WITS

ISSA

NYPT

ACSM

AOTA

REPSI

PTAGlobal

AFAA

CanFitPro

This course discusses circuit training (a.k.a. circuits, vertical loading, giant sets, exercise in-circuit, exercise in sequence, etc.). The course details the <a id="evidence-based-practice" data-tip="1538" target="_blank" href="/glossary-term/evidence-based-practice" class="glossary">evidence-based</a> recommendations for optimizing circuit training workouts, especially as an alternative to the long rest between sets for the same <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> group required to optimize workout performance. Research and sample routines are discussed for all training goals, including <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> endurance, <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> strength, increased <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> mass (hypertrophy), <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> and speed, functional outcomes, and corrective exercise. A systematic research review covers the benefits of circuit training including training goals, body composition, and mental health benefits, and compares circuit training to aerobic exercise (including cardio, heart rate, VO2 max, respiration, etc), and conventional strength training routines.
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 circuit training 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">Acute Variables: Rest Between Sets</a></li>
</ul>
<h3>Brookbush Institute Position Statement: Circuit Training</h3>
The Brookbush Institute recommends implementing circuit training for nearly all resistance training goals. When compared to conventional resistance training, circuit training results in similar intensity and volume of exercise during a session (similar number of reps/set, loads lifted, and peak and average power/rep), and similar outcomes following several weeks of training (improvements in body composition, hypertrophy, endurance, maximum strength, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, agility, <a id="balance" data-tip="1190" target="_blank" href="/glossary-term/balance" class="glossary">balance</a>, and functional outcomes). The advantage of circuit training protocols is a reduction in session time by 35 - 60 percent. This is especially true when attempting to allow for an ideal amount of <a href="https://brookbushinstitute.com/courses/acute-variables-rest-between-sets">rest between sets</a> <a href="https://brookbushinstitute.com/courses/acute-variables-rest-between-sets" target="_blank" rel="noopener"></a>for similar <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> groups (2-3 minutes); even when allowing for an ideal amount of rest between exercises during circuit training (30 - 60 seconds).
<h3>Evidence-based Circuit Training Recommendations:</h3>
<ul>
 <li>Vertical loading; that is, e<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;">ach exercise is performed sequentially, and then the next set of each exercise is completed, repeat.</li>
 <li>Circuits should be comprised of 3 or more exercises (2 exercises will not allow enough rest between sets of the same exercise).</li>
 <li>30 &#x2013; 60 seconds of rest between exercises may aid in optimizing set quality when reps are performed until failure (reps/set and repetition tempo). More extended rest may be taken between circuits, as needed.</li>
 <li>Exercise selection, load, reps/set, sets/exercise, and repetition tempo should match your goal (it is not necessary to alter these acute variables to adopt a circuit training routine).</li>
</ul>
<img title="Dr. Brent Brookbush demonstrating a pushup exercise with resistance" src="https://www.datocms-assets.com/25800/1649792750-push-up.png" alt="Push-ups using a band as resistance">

Course Description: Acute Variables - Circuit Training

Circuit Training Webinar

<h2>Position Statement</h2>
The Brookbush Institute recommends the adoption of circuit training for nearly all resistance training goals. When compared to conventional resistance training, circuit training results in similar intensity and volume of exercise during a session (similar number of reps/set, loads lifted, and peak and average power/rep), and similar outcomes following several weeks of training (improvements in body composition, hypertrophy, endurance, maximum strength, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, agility, <a id="balance" data-tip="1190" target="_blank" href="/glossary-term/balance" class="glossary">balance</a>, and functional outcomes). The advantage of circuit training protocols is a reduction in session time by 35 - 60 percent. This is especially true when attempting to allow for an ideal amount of <a href="https://brookbushinstitute.com/courses/acute-variables-rest-between-sets">rest between sets</a> <a href="https://brookbushinstitute.com/courses/acute-variables-rest-between-sets" target="_blank" rel="noopener"></a>for similar <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> groups (2-3 minutes); even when allowing for an ideal amount of rest between exercises during circuit training (30 - 60 seconds).
<h2>Definitions:</h2>
<h3>Conventional Training (a.k.a. horizontal loading):<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;"> </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;">Horizontal loading is when all sets for a given exercise are done before moving on to the next exercise. Historically/conventionally, this has been the most recommended method for resistance training routines.
<ul>
 <li>Disadvantage:<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 <a id="optimal" data-tip="1571" target="_blank" href="/glossary-term/optimal" class="glossary">optimal</a> rest between sets is performed (2-3+ min) conventional training can result in very long session durations, or relatively low exercise volumes if session durations are fixed.</li>
 <li>Example:<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;"> Bench press, rest, bench press, rest, bench press, rest, then progress to the next exercise; seated row, rest, seated row, rest, seated row, rest; then on to the next exercise (repeat).</li>
</ul>
<h3>Circuit Training/Vertical Loading:<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;"> </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 the first set of each exercise is performed sequentially, and then the next set of each exercise is performed, repeat.
<ul>
 <li>Advantage:<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 long rest between sets is used to address other exercises, and/or different <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> groups. Session time is reduced, but each <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> group is still allowed an ideal amount of rest between sets (or more, which does not negatively impact performance).</li>
 <li>Example:<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;"> Bench press, seated row, leg press, rest, bench press, seated row, leg press, rest (repeat).</li>
</ul>
&#xA0;<img alt="Dr. Brent Brookbush cues Melissa through multi-planer dumbbell press on bench" title="Dr. Brent Brookbush cues Melissa through multi-planer dumbbell press on bench" src="https://www.datocms-assets.com/25800/1632846046-dumbbell-press.jpg" width="500" height="429">
<h2>Circuit Training Practical Application</h2>
<h3>Recommendations:</h3>
<ul>
 <li>30 &#x2013; 60 seconds rest between exercises aids in optimizing set quality when reps are performed until failure (reps/set and repetition tempo). Longer rest may be taken between circuits, as needed.</li>
 <li>Circuits should be comprised of 3 or more exercises (2 exercises will not allow enough rest between sets of the same exercise).</li>
 <li>Exercise selection, load, reps/set, sets/exercise, and repetition tempo should match your goal (it is not necessary to alter these acute variables to adopt a circuit training routine).</li>
</ul>
&#xA0;
<h2>Sample Routine:</h2>
<h3>Goal: Upper Body Max Strength</h3>
<ul>
 <li>Acute Variables: 
 <ul>
 <li>Load: Heavy (&gt; 85% of 1-RM)</li>
 <li>Reps/set: 1-5 reps</li>
 <li>Sets/exercise (circuits): 2-5 circuits</li>
 <li>Rest between exercises: 60 seconds</li>
 <li>Training Time: 20 &#x2013; 45 minutes (excluding warm-up).</li>
 </ul>
 </li>
</ul>
<ul>
 <li>Routine:
 <ul>
 <li>Chest: <a href="https://brookbushinstitute.com/videos/bench-press-chest-press" target="_blank" rel="noopener">Bench Press</a></li>
 <li>Back: <a href="https://brookbushinstitute.com/videos/row-and-progressions" target="_blank" rel="noopener">Seated Row</a></li>
 <li>Shoulders: <a href="https://brookbushinstitute.com/videos/overhead-press">Dumbbell Overhead Press</a></li>
 <li>Corrective (activation/not <a id="mobility" data-tip="1455" target="_blank" href="/glossary-term/mobility" class="glossary">mobility</a>): <a href="https://brookbushinstitute.com/videos/standing-cobra" target="_blank" rel="noopener">Standing Band ITYs</a></li>
 </ul>
 <a href="https://brookbushinstitute.com/videos/standing-cobra" target="_blank" rel="noopener"> </a>
 </li>
</ul>
<ul>
 <li>Additional Notes on the Sample Routine:
 <ul>
 <li>Take your time between exercises (60 sec)</li>
 <li>Each circuit is likely to take 6 - 8 min</li>
 <li>Heart rate (HR) and rate of perceived exertion (RPE) may be higher than in conventional training.</li>
 <li>Despite higher RPE, set performance should be similar (number of reps to failure, load, bar velocity, etc).</li>
 <li>It may take 2 &#x2013; 4 sessions to &#x201C;get used to&quot; circuit training. Don&#x2019;t give up after a single session. The time saved, and/or increase in volume/session, is worth the adjustment period!</li>
 </ul>
 </li>
</ul>

<h2>Circuit Training Quick Summary</h2>
<ul>
 <li>Circuit Training Compared to Aerobic Exercise:&#xA0;Sedentary individuals performing circuit resistance training may initially improve aerobic performance; however, experienced exercisers and sedentary individuals who intend to make additional improvements will require a progressive, moderate to high intensity, aerobic exercise routine. This may be especially true of improvements in VO2max. Further, all exercisers may achieve larger aerobic benefits from aerobic training, or the combination of circuit strength training and aerobic training.</li>
 <li>Caloric Expenditure:&#xA0;Caloric expenditure is similar for work-matched strength training routines with conventional or circuit training protocols. Aerobic exercise results in more caloric expenditure than strength training when matched for average heart rate and session duration, despite strength training resulting in a larger increase in excess post-exercise oxygen consumption (EPOC).</li>
</ul>
<img title="A lateral lunge holding kettlebells in a front rack position" src="https://www.datocms-assets.com/25800/1649424090-lateral-lunge-with-front-rack-squat.jpg" alt="A frontal plane lunge holding kettlebells">
<ul>
 <li>Body Composition: Circuit training for less than 8-weeks, with low or moderate intensity, low or moderate volume, and/or with hydraulic/isokinteic equipment, is likely insufficient to significantly change body composition (especially body fat%). Changes in body composition are more likely when circuit training is longer than 8 weeks, performed in combination with aerobic or sport activity, is high intensity and/or high volume, and progresses over time (e.g. periodization).</li>
 <li>Mental Benefits: Even when circuit training has yet to result in statistically significant improvements in circumference measurements, body fat, or weight measures, significant improvements may be achieved for body image, mental health, and job satisfaction.</li>
 <li>Addition of Circuit Training to Sport, Occupation, or Gym Class: The addition of circuit training to sport training, physically demanding occupations, and or gym class (9 -14 years old) is likely to significantly improve endurance, strength, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, agility, and potentially body composition and hypertrophy. Some &quot;experimentation&quot; in programming may be warranted as strength training exercises immediately prior to some sports may negatively impact performance (e.g. basketball); however, strength training exercises may be more beneficial for sports that already incorporate a large volume of <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> movements (e.g. volleyball).</li>
 <li>Load Over Volume:&#xA0;Load may have a larger influence than volume on improving strength, endurance, body composition, and various serum concentrations associated with general health.&#xA0;Untrained individuals may achieve similar benefits from training with low loads, high loads, low volume, or high volume for up to 12 weeks; however, beyond 12 weeks, load and volume should increase to achieve additional benefits. Further, athletes with the goal of increasing speed are likely to achieve larger improvements following maximal tempos with lighter loads, when compared to heavier load training.</li>
 <li>Comparing Routines: Some <a id="specificity" data-tip="1223" target="_blank" href="/glossary-term/specificity" class="glossary">specificity</a> can be expected from circuit training exercise selection, including free weight (functional) routines having a larger effect on strength <a id="assessment" data-tip="1478" target="_blank" href="/glossary-term/assessment" class="glossary">assessment</a> using free weight exercises, larger loads lifted (with machines) resulting in larger increases in grip strength, lighter loads and faster/explosive repetition tempos resulting in larger increases in <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, speed and agility training resulting in larger improvements in speed and agility, and the addition of <a id="stability" data-tip="1191" target="_blank" href="/glossary-term/stability" class="glossary">stability</a> exercise resulting in larger improvements in abdominal strength, <a id="balance" data-tip="1190" target="_blank" href="/glossary-term/balance" class="glossary">balance</a> and functional outcomes in an elderly population.</li>
 <li>Compared to Conventional Training:&#xA0;During a session, circuit training results in higher peak HR, average HR, and peak O2 consumption, but a similar number of reps/set (exercise volume), peak and average bar velocity, and peak and average <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>. Following weeks of training, conventional and circuit training protocols result in similar improvements in body composition, hypertrophy, endurance, maximum strength, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, and agility.</li>
 <li>Exercise Order:&#xA0;The order of aerobic and strength training exercise only results in small differences; however, if cardiovascular performance or total caloric expenditure is the priority, aerobic training should be performed first, and if strength is the priority it may be advised to perform strength training alone. Exercises programmed at the beginning of a routine are likely to be performed with more reps/set.</li>
 <li>Comparing Rest Between Exercises:&#xA0;Although more reps/set may be performed during circuit training with longer rest between exercises (60 sec vs. 30 sec), these benefits should be compared to the potential for more sets performed during a session with a fixed duration.</li>
</ul>

Circuit Training Research Summary

<ul>
 <li>Circuit Training Compared to Controls: Obese, active, and athletic individuals performing 6-12 weeks of circuit training, with or without equipment, may significantly improve cardiovascular performance. Improvements may include enhanced respiratory rate, blood pressure (BP), resting heart rate (HR), partial O2 saturation,&#xA0;VO2 max, maximal ventilation (VEmax), stroke volume, rate of lactate removal, HR for a given sub-maximal workload, treadmill endurance times, Cooper 12 minute walk/run <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a> distance, and 1,600 m run times.
 <ul>
 <li>Increasing Loads: Increasing load and intensity are likely to increase the cardiovascular benefits of circuit training; however, circuit training alone may not be ideal for improving cardiovascular health.</li>
 </ul>
 </li>
 <li>Circuit Training Compared to Low-intensity Aerobic Exercise: High-intensity circuit training (e.g. &quot;max effort/set&quot;), even when session lengths are shorter, may result in larger improvements of HR, VO2 max, and aerobic endurance, when compared to low-intensity aerobic activity (e.g. walking).</li>
 <li>Circuit Training Compared to Higher Intensity Aerobic Exercise
 <ul>
 <li>Specific Adaptations to Imposed Demands (SAID Principle): Circuit resistance training is likely to result in improvements in strength but may not influence VO2 max, and moderate to high-intensity aerobic exercise is likely to result in significant improvements in VO2 max but may not influence strength.</li>
 <li>Cross-over: Sedentary individuals performing circuit resistance training may initially attain strength and aerobic benefits; however, larger aerobic performance improvements may be attained from aerobic activity. Further, when circuit and aerobic training programs are combined, benefits may be seen for strength and aerobic performance.</li>
 </ul>
 </li>
 <li>Circuit Training Compared to Aerobic Exercise: Work-matched Routines
 <ul>
 <li>Single Session:&#xA0;These studies demonstrate that work-matched circuit resistance training and aerobic activity may result in similar peak HR, O2 consumption, EPOC, blood glucose and triglycerides. However, aerobic activity performed with the same O2 consumption as a circuit training routine results in a lower HR, ventilation rate, and rate of perceived exertion (RPE), and aerobic activity with a similar HR as circuit training burns more calories.</li>
 <li>Outcomes Following Weeks of Training: Circuit resistance training is likely <a id="superior" data-tip="1570" target="_blank" href="/glossary-term/superior" class="glossary">superior</a> for strength improvements when compared to aerobic training. Further, increases in cardiovascular performance are likely similar when comparing circuit training and aerobic activity with the intensity matched by average % of max HR. However, it should be noted that matching circuit training and aerobic exercise by % of max HR likely limits aerobic activity intensity to the average HR that can be achieved during circuit training. It is likely that if aerobic exercise is matched to circuit training by RPE, the result would be a higher % of max HR and larger improvements in cardiovascular performance achieved from aerobic activity.</li>
 </ul>
 </li>
 <li>Combined Aerobic and Strength Exercise:&#xA0;Improvements in performance are likely similar when combining aerobic training and resistance training into the same circuit, same session, or sequentially in the same program. However, it may be <a id="optimal" data-tip="1571" target="_blank" href="/glossary-term/optimal" class="glossary">optimal</a> for aerobic performance to perform aerobic activity prior to resistance training and may be <a id="optimal" data-tip="1571" target="_blank" href="/glossary-term/optimal" class="glossary">optimal</a> for maximal strength to perform strength training alone (without aerobic activity in the same session).</li>
</ul>

<h3>Physiology</h3>
<ul>
 <li>Blood Glucose and Lipid Profiles:&#xA0;Resistance training, including circuit training, can have a significant effect on triglycerides, total cholesterol and potentially glucose; however, circuit training may have little effect on HDL/LDL ratio. Further, some, or all of these benefits may be achieved with as little as 7 minutes of circuit training/day.</li>
 <li>Metabolic Markers:&#xA0;Circuit training may have a positive effect on some, but not all markers of metabolic function. Positive effects were noted for serum concentrations of chemrin, serum amyloid A, insulin (insulin resistance index), Lipocalin-2, obestatin, and the ghrelin/obestatin ratio. However, no significant effects were noted for insulin <a id="sensitivity" data-tip="1226" target="_blank" href="/glossary-term/sensitivity" class="glossary">sensitivity</a>, or serum concentrations of glucose,&#xA0;irisin, apelin, ghrelin, or c-reactive protein (including high-sensitivity c-reactive protein testing).</li>
 <li>Immune Function:&#xA0;Circuit training, with or without probiotic supplementation, is unlikely to have a significant short-term effect on immune function, based on post-exercise&#xA0;concentrations of salivary&#xA0;IgA, &#x3B1;-amylase, lactoferrin, total leukocytes, total lymphocytes, T-lymphocytes, T-helper, T-cytotoxic, B lymphocytes, and natural killer cells counts. The one potential exception is IL-10 concentrations.</li>
 <li>Growth Hormones:&#xA0;Circuit training may have a significant influence on some, but not all <a id="hormone" data-tip="1268" target="_blank" href="/glossary-term/hormone" class="glossary">hormones</a> associated with bone growth, <a id="hypertophy" data-tip="1233" target="_blank" href="/glossary-term/hypertophy" class="glossary">muscle growth</a>, and cognition. This includes increases in post-exercise serum concentration of growth <a id="hormone" data-tip="1266" target="_blank" href="/glossary-term/hormone" class="glossary">hormone</a>, estrogen, and parathyroid <a id="hormone" data-tip="1266" target="_blank" href="/glossary-term/hormone" class="glossary">hormone</a>, but no change in concentrations of IGF-1, and inconsistent changes in concentration of brain-derived neurotrophic factor (BDNF), testosterone, cortisol, or testosterone/cortisol ratio.</li>
</ul>
<h3>Caloric Expenditure</h3>
<ul>
 <li>Comparing Gender and Load:&#xA0;Men and women burn calories at a similar rate when calculated based on kcal/lean body weight, and significant increases in load result in a significant increase in caloric expenditure (Note, as discussed below, the difference in caloric expenditure is statistically significant, but relatively small).</li>
 <li>Comparing and Combining Circuit Resistance Training and Aerobic Training:&#xA0;Circuit training burns fewer calories than aerobic training when routines are matched by average HR and session duration; further, HIIT sets before a circuit routine burns slightly more calories than HIIT sets in a circuit routine.</li>
 <li>Excess Post-exercise Oxygen Consumption (EPOC)
 <ul>
 <li>Comparing Circuit Training and Aerobic Exercise:&#xA0;Heavy circuit training may result in more calories burned than light circuit training, and circuit training may result in more EPOC than aerobic exercise; however, the differences in calories burned is small (approximately 20 total calories).</li>
 <li>Comparing Circuit Training and Conventional Resistance Training (as well as different loads and volumes):&#xA0;EPOC is similar following circuit training and conventional resistance training, even when loads and volumes are very different. Although circuit training (when compared to conventional training), heavier loads, and larger volumes of exercise may increase EPOC and caloric expenditure, the difference in calories burned is 10 - 20 calories/session.</li>
 </ul>
 </li>
</ul>
<h3>Body Image Studies:</h3>
<ul>
 <li>Summary:&#xA0;Even when circuit training has yet to result in statistically significant improvements in circumference measurements, body fat, or weight measures; significant improvements in body image may be achieved. These changes may include a decrease in the discrepancy between perceived current body image and ideal body image,&#xA0;self-evaluation of appearance, body satisfaction, social physique anxiety, and physical self-efficacy. Additionally, circuit training may result in significant improvements in mood, including decreases in somatization, anxiety, depression, hostility, and job satisfaction. Further, it is worth noting that the studies demonstrating these findings included a wide variety of participants from 14 - 47 years old, students, professionals, active individuals, and previously sedentary individuals.</li>
</ul>
<h3>Body Composition</h3>
<ul>
 <li>No Change in Body Composition:&#xA0;Circuit training for 8 weeks, 2-4 circuits/session, with moderate resistance, may be insufficient to significantly alter body composition, despite significant improvements in strength and cardiovascular performance.</li>
 <li>No Change with Hydraulic and Isokinetic Equipment: Circuit training with hydraulic or isokinetic equipment, for 12- 13 weeks, is unlikely to result in improvements in body composition or circumference measurements. Additionally, circuit training with this equipment may result in relatively small improvements in strength.</li>
 <li>Trending Toward Body Fat Percentage Improvements:&#xA0;Some studies fail to demonstrate clear evidence of body fat % improvements; however, they may demonstrate trends toward improvement, and significant improvements of related outcome measures (skinfold, circumference, and lean body weight measurements), suggesting that circuit training (10 weeks, 3x/week) has the potential to improve body composition.</li>
 <li>Significant Changes in Body Fat Percentage:&#xA0;Contrary to the research discussed above, these studies suggest that both overweight and athletic individuals may achieve significant changes in body fat % following just 8 weeks of circuit training. It is worth noting that these studies included circuit training protocols, or a combination of circuit training and sport, that resulted in high volumes of activity.</li>
 <li>What Type of Circuit Training is Best for Altering Body Composition?&#xA0;Functional exercises, conventional resistance training exercises, and circuit training with or without rest between exercises likely result in similar improvements in body composition.</li>
 <li>What Acute Variables Most Influence Body Composition?&#xA0;Larger decreases in body fat % may follow training with higher intensity (load), higher volume (total sets), and/or performed with a circuit protocol. It may be worth noting that the protocols resulting in the largest changes, were often more detailed and progressed over time.</li>
 <li>Comparing Circuit Training and Aerobic Training for Body Composition:&#xA0;Circuit training and aerobic training may be equally effective at reducing body fat %. However, some evidence suggests circuit training may be more effective, in part due to larger increases in lean body mass.</li>
 <li>Combining Circuit Training and Aerobic Training and Body Composition: The addition of 30 seconds of running between stations of a circuit training routine is likely insufficient to result in additional improvements in body composition. However, following 8 weeks of circuit training or aerobic training, an additional 8 weeks of aerobic training was more likely to result in additional improvements in body composition when compared to circuit training.</li>
</ul>

<h3>Addition of Circuit Training to Sport and Occupation</h3>
<ul>
 <li>Basketball:&#xA0;The addition of strength or <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> circuit training to a basketball program is effective for improving endurance, strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> in children, teenagers, and young adults. However, it may be recommended that <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> circuits, and not maximal strength circuits, are performed before basketball practices or games.</li>
 <li>Soccer:&#xA0;The addition of circuit training is beneficial for football (soccer) players; however, they may improve more from endurance and strength exercise, when compared to <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercises.</li>
 <li>Handball:&#xA0;For handball athletes, replacing some sports <a id="specificity" data-tip="1224" target="_blank" href="/glossary-term/specificity" class="glossary">specific</a> training, or adding circuit training, may significantly improve <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> endurance, strength, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, agility, and potentially body composition and hypertrophy.</li>
 <li>Volleyball and Tennis:&#xA0;The addition of circuit training may result in significant increases in endurance, strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, and may be more beneficial than <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> training for volleyball and tennis athletes.</li>
 <li>Mixed Sports:&#xA0;Even when athletes are involved in a mix of sports they may attain significant improvements in speed, agility and heart rate recovery with the addition of a circuit training routine.</li>
 <li>Occupation:&#xA0;Firefighters, law enforcement officers, and military recruits, following 4 - 16 weeks of circuit training, may improve <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> endurance, strength, <a id="balance" data-tip="1190" target="_blank" href="/glossary-term/balance" class="glossary">balance</a>, conditioning, cardiovascular health measures, mental health, and job satisfaction; without an increase in the risk of injury.</li>
</ul>
<img src="https://www.datocms-assets.com/25800/1661643047-soccer-compressed.jpg" title="A soccer player taking a shot with a powerful kick" alt="A soccer player taking a free kick">
<h3>Young Children</h3>
<ul>
 <li>Circuit Training is Effective:&#xA0;Circuit training is an effective intervention for improving speed and agility in young children; however, more research is needed to determine the influence of exercise selection on outcomes.</li>
 <li>Circuit Training added to Activity:&#xA0;The addition of circuit training to organized sports or gym class may improve the endurance, strength, speed, agility, and fitness battery tests of young children. Further, larger improvements may be attained from higher intensity activity, and some of these improvements may be retained following a period of detraining and/or maintenance.</li>
</ul>
<h3>Hypertrophy</h3>
<ul>
 <li>Compared to Controls:&#xA0;When compared to controls (no additional activity), circuit training is an effective method for increasing lean body mass and <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> hypertrophy, even when training is followed by a significant period of de-training. Specifically, circuit resistance training has a significant effect on the proportion and size of type IIa <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> fibers.</li>
 <li>Compared to Other Types of Training:&#xA0;Circuit training, conventional resistance training, and high-intensity functional exercise training, result in similar changes in performance, body fat %, and lean body mass.</li>
 <li>Compared to Aerobic Training: Circuit training results in larger improvements in lean body mass, hypertrophy, and <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> strength, when compared to aerobic training.</li>
 <li>Comparing Normoxic and Hypoxic Environments:&#xA0;Hypoxic and normoxic environments likely result in similar improvements in strength and hypertrophy. However, some evidence suggests that training in hypoxic environments may augment benefits, which may have implications for resistance training at higher altitudes.</li>
 <li>Increasing Volume: The addition of circuit training to sport is likely to increase lean body mass and hypertrophy, and although a single set of circuit training may be sufficient to increase lean body mass for up to 12 weeks, additional sets should be added to attain additional improvements beyond 12 weeks.</li>
</ul>

<h3>Load and Volume</h3>
<ul>
 <li>Load Over Volume:&#xA0;Load may have a larger influence than volume on improving strength, endurance, body composition, and various serum concentrations associated with general health. However, lower load (higher volume) routines may be more beneficial for improving systolic blood pressure.
 <ul>
 <li>Exceptions:&#xA0;Untrained individuals may achieve similar benefits from training with low loads, high loads, low volume, or high volume for up to 12 weeks; however, beyond 12 weeks, load and volume should increase to achieve additional benefits. Further, athletes with the goal of increasing speed are likely to achieve larger improvements following maximal tempos with lighter loads, when compared to heavier load training.</li>
 </ul>
 </li>
 <li>Micro Sessions (6 - 14 min sessions):&#xA0;These studies suggest that some benefit may be attained from daily 6 - 7 min circuit training sessions, including subjective reports of improved health, an increase in reps/set for the exercises performed in the circuit, some benefits for post-exercise concentrations of glucose and blood triglycerides, and 14-minutes may be enough for some initial improvements in aerobic performance. However, it would appear that the volume of exercise is insufficient to improve most measures of strength, cardiovascular performance, and body composition.</li>
</ul>
<h3>Comparing Routines</h3>
<ul>
 <li>Functional Training versus Conventional Training:&#xA0;Functional training (as the term is currently being used in the fitness industry) and conventional training are likely to result in similar improvements in endurance, strength, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, cardiovascular performance, body composition, and mental health. However, some <a id="specificity" data-tip="1223" target="_blank" href="/glossary-term/specificity" class="glossary">specificity</a> can be expected, including free weight (functional) routines having a larger effect on strength <a id="assessment" data-tip="1478" target="_blank" href="/glossary-term/assessment" class="glossary">assessment</a> using free weight exercises, larger loads lifted (with machines) resulting in larger increases in grip strength, and the addition of low-intensity (high volume) exercise improving feelings of general physical well-being.</li>
 <li>Comparing <a id="stability" data-tip="1194" target="_blank" href="/glossary-term/stability" class="glossary">Unstable</a> Environments/Loads and Conventional Exercise Selection:
 <ul>
 <li>Teenagers and Young Adults:&#xA0;The addition of <a id="stability" data-tip="1194" target="_blank" href="/glossary-term/stability" class="glossary">Unstable</a> environments and loads may result in similar strength, endurance and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> improvements, but may additionally result in <a id="superior" data-tip="1570" target="_blank" href="/glossary-term/superior" class="glossary">superior</a> improvements for <a id="balance" data-tip="1190" target="_blank" href="/glossary-term/balance" class="glossary">balance</a> and abdominal strength.</li>
 <li>Older Adults:&#xA0;Although the available research lacks comparison to conventional exercise selection, the research suggests that elderly individuals performing circuit training with <a id="balance" data-tip="1190" target="_blank" href="/glossary-term/balance" class="glossary">balance</a> and <a id="stability" data-tip="1191" target="_blank" href="/glossary-term/stability" class="glossary">stability</a> exercises are likely to exhibit significant increases in strength, endurance, <a id="balance" data-tip="1190" target="_blank" href="/glossary-term/balance" class="glossary">balance</a>, and subjective health, as well as improvements on functional outcomes measures (e.g. timed up-and-go <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>, 30-s chair stand, 6-min walk <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>,&#xA0;rapid gait <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>, stand-up <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>, and Barthel Index Scores).</li>
 </ul>
 </li>
 <li>Comparing Circuit Training and Physically Demanding Occupations (Fire-fighting and Fight Sports): Circuit training can closely mimic the anaerobic stress and physiological response correlated with fight sports and fire-fighting; however, a study comparing circuit training and fire-fighting may suggest circuit training is not ideal for matching aerobic demands.</li>
 <li>Hydraulic/Isokinetic&#xA0;Equipment:&#xA0;Hydraulic/isokinetic equipment is a relatively poor choice for resistance training, resulting in relatively small changes in body composition, strength, endurance and speed. Further, even when strength is tested with concentric force only, concentric only repetitions may result in <a id="inferior" data-tip="1569" target="_blank" href="/glossary-term/inferior" class="glossary">inferior</a> improvements when compared to conventional concentric and eccentric resistance training.</li>
</ul>
<h3>Comparing Strength and Power</h3>
<ul>
 <li>Endurance Athletes:&#xA0;Compared to bodyweight circuit training, conventional max strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training result in <a id="superior" data-tip="1570" target="_blank" href="/glossary-term/superior" class="glossary">superior</a> improvements for&#xA0;explosive strength,&#xA0;maximal strength, <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> activation, jump height, and peak running speed. However, the improvements in VO2 max noted in some circuit training studies may imply that additional research should investigate the combination of strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercises performed with a circuit protocol.</li>
 <li>Sprinters: Peak running speed and sprint times are likely to improve more following fast tempo or <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training exercises, when compared to slow tempo or conventional strength training exercises.</li>
 <li>Specificity: Faster training speeds are less likely to have an immediate detrimental effect on <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, agility, and <a id="accuracy" data-tip="1218" target="_blank" href="/glossary-term/accuracy" class="glossary">accuracy</a>. Depth jumps are likely to result in larger improvements than a mixed jumping program for max jump height and distance (especially for event athletes). And, speed and agility training are likely to result in larger improvements in speed and agility, while strength training is likely to result in larger improvements in <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> endurance.</li>
</ul>
<h3>Compared to Conventional Strength Training</h3>
<ul>
 <li>Single Session Comparison:&#xA0;During a session, circuit training results in higher peak HR, average HR, and peak O2 consumption, but a similar number of reps/set (exercise volume), peak and average bar velocity, and peak and average <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>. Further, circuit training protocols may reduce session time by 35 - 60 percent.</li>
 <li>Outcomes Following Training Routines (6+ weeks):&#xA0;Conventional resistance training protocols (long rest between sets) and circuit training protocols (short rest between exercises) are likely to result in similar improvements in lean body mass, maximum strength, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, and agility following 6 - 15 weeks of training. However, circuit training may result in some additional functional benefits (improvement of SPBB scores) for older adults.</li>
 <li>VO2 Max:&#xA0;Circuit training and conventional resistance training result in similar improvements in VO2 max, and that these improvements are likely <a id="inferior" data-tip="1569" target="_blank" href="/glossary-term/inferior" class="glossary">inferior</a> to a progressive aerobic training program.</li>
 <li>Body Composition:&#xA0;Performing conventional strength training in circuit may result in a small but significant increase in caloric burn, body composition, and cardiovascular performance.</li>
</ul>
<h3>Exercise Order</h3>
<ul>
 <li>Aerobic Training or Strength Training First?&#xA0;The order of aerobic and strength training exercise only results in small differences; however, if cardiovascular performance or total caloric expenditure is the priority, aerobic training should be performed first, and if strength is the priority it may be advised to perform strength training alone.</li>
 <li>Order of Resistance Training Exercises: Exercises programmed at the beginning of a routine are likely to be performed with more reps/set, and there is little difference in caloric burn between upper/lower routines (peripheral heart action) and pre-exhaustion routines (compound movement followed by single joint exercise).</li>
</ul>
<h3>Additional Studies</h3>
<ul>
 <li>Comparing Rest Between Exercises:&#xA0;Although more reps/set may be performed with longer rest between exercises (60 sec vs. 30 sec), these benefits should be compared to the potential for more sets performed during a session with a fixed duration.</li>
 <li>Increased Strength without a Loss of Range of Motion: The findings of a study by Monteiro et al. (2008) demonstrated that circuit training resulted in significant improvements in strength, and no decrease in flexibility for any of the 10 range of motions tested (including shoulders, hips, and spine).</li>
 <li>Hypoxic Versus Normoxic Environments:&#xA0;Hypoxic environments may result in an acute decrease in strength training performance, an increase in caloric expenditure immediately following training, and may result in some long-term benefits for cardiovascular performance variables. However, the difference between improvements made for strength and hypertrophy following training in hypoxic and normoxic environments are likely small, if there is any difference at all.</li>
 <li>Skin Temperature: Based on findings from a study by&#xA0;Viera et al. (2020), resting skin temperature was higher for men than women, circuit training did not have a significant effect on average skin temperature 20 min post-exercise; however, skin temperature was elevated in the upper back of men and quadriceps of woman 24 hours post-exercise.</li>
 <li>Altered <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">Muscle</a> Activity: A study by Jeong et al. (2020) demonstrated that circuit training resulted in an increase in quadriceps and hamstrings strength. Further, during a side-stepping cutting maneuver, the circuit training group exhibited an altered activation ratio of the quadriceps/hamstrings, decreased gastrocnemius activity during the pre-activation phase, without a significant change in lower extremity kinematics (functional valgus and <a id="anterior" data-tip="1566" target="_blank" href="/glossary-term/anterior" class="glossary">anterior</a> <a id="glide" data-tip="1817" target="_blank" href="/glossary-term/glide" class="glossary">shear</a> force).</li>
</ul>

Circuit Training and Cardiovasular Performance

<h4>Bodyweight Only</h4>
Several studies have demonstrated that circuit training alone, with little or no equipment, may result in significant improvements in cardiovascular performance when compared to no additional activity. Kaur et al. compared 40 teenagers (age: 16 &#xB1; 2 years) randomly assigned to a control group (no additional activity) and a circuit training group. The circuit training included 9 exercises (shuttle run, leg splitting, skipping, 30 m sprint, high knees, stair exercises, squat jumps, hops, and vertical jumps) for 12 weeks, 4 days/week, 30 sec/set, 40 sec rest between exercises, 2 circuits/session, and 5 minutes rest between circuits. The findings demonstrated significant increases in aerobic capacity (VO2 max), 50m sprint times, and vertical jump height (1). Ikenna et al. compared 60 healthy females (age: 17 - 30 years) randomly assigned to a control group (no additional activity), or a circuit training group. Circuit training was performed for 6 weeks, 3x/week, included 6 exercise stations (lunges, curtsy lunges, torso rotation, knee raise claps, abdominal twist or knee combo, kick raises), with &quot;short&quot; rest between stations, and 35-55 min/session (increased by 10 min/2 week period). The findings demonstrated that the circuit training group exhibited significant improvements in hip circumference and cardiovascular measures, including respiratory rate, blood pressure (BP), resting heart rate (HR), VO2 max, and partial oxygen saturation (2). Khattak et al. compared 30 students (age: 18 - 22 years) randomly assigned to control (no additional activity) and circuit training groups. The circuit training included 10 exercises (light jumping, lunges, legs raising, high-knees, sit-ups with straight legs, crunches, heel raising, burpees, squats (abdominal), and jumping jacks) performed for 12 weeks, 3x/week, 2 circuits/session, a progressive increase from 30-60 sec/set, progressive increase in rest between exercise from 20 - 35 sec, rest between circuits progressed from 4 - 4.5 min, and a target HR of 55-65% of max HR for weeks 1-6, and 65-75% of max HR for weeks 7-12. The findings demonstrated that the circuit training group exhibited significant improvements in cardiovascular endurance based on the Cooper 12 minute walk/run <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a> (increased distance post training) (3). Last, Kim et al. compared 20 obese (30% of accumulated body fat) female college students (age: circuit 22.90&#xB1; 2.23, control 24.50&#xB1; 1.72 years) randomly assigned to a control group (no additional activity) or circuit training group. The circuit training included 10 stations (push-ups, squats, crunches, lunges, supermans, and aerobic activity including light jumping, running on the spot, foot stamping, steps, and jumping jacks), performed for 12 weeks, 3x/week. The findings demonstrated that compared to controls, circuit training resulted in improvements in back strength, sit-ups for reps, sit-and-reach flexibility, and 1,600 m run time (4). These studies demonstrate that 12 weeks of circuit training, with little to no equipment, resulted in significant improvements in cardiovascular performance, including respiratory rate, blood pressure (BP), resting HR, VO2 max, partial oxygen saturation, Cooper 12 minute walk/run <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>, and 1,600 m run times.
<img title="Pushup with Band Resistance" src="https://www.datocms-assets.com/25800/1644608333-push-up.png">
<h4>With Equipment</h4>
Additional studies demonstrate that circuit training with various types of resistance may also improve cardiovascular performance. Sonchan et al. compared 24 male college students (age: 18.87+0.68 years) randomly assigned to a control group (no exercise) or a circuit training group. The circuit training group performed an 8 station routine (battle ropes, single-leg hops, leg raises, barbell squats with 50lb, jump squats, shoulder press with 15lb dumbbells, triceps dips, and bear crawls) for 8 weeks, 3x/week, weeks 1-4: 2 circuits/session, with 30/60 sec work/rest ratios, weeks 5-8: 3 circuits/session with 60/90 sec work/rest ratios. The findings demonstrated that the circuit training group exhibited significant improvements in strength, aerobic performance, and agility when compared to controls (5). Petersen et al. compared 16 active males randomly assigned to a control group (no additional training) or a circuit training group. Circuit training included 10 variable-resistance hydraulic exercise stations, performed for 6 weeks, 3 days/week, 2 - 3 circuits/session, 2:1 work/rest ratio, and tempo 3.1 rad/sec. The findings demonstrated a significant increase in maximal oxygen consumption (VO2 max), stroke volume, and removal of lactate, as well as a decrease in HR for a given sub-maximal workload (6). Wilmore et al. compared 49 men and women (age: 17 - 36 years old), randomly assigned to a control group (no additional activity) or a circuit training group. Circuit training included 10 exercises on a universal gym, performed for 10 weeks, 3x/week, 3 circuits/session, max reps in 30 sec/set, 40-55% of 1-RM loads, 15 sec rest between sets, and 22.5 minutes/session. The findings demonstrated significant improvements in resting HR, treadmill endurance time, maximal ventilation (VEmax), and VO2max (woman only). Generally, women exhibited larger improvements than men (7). These studies suggest that the addition of circuit training for 6 - 12 weeks, performed by obese, sedentary, or active individuals, may significantly improve cardiorespiratory performance, including resting HR, respiratory rate, blood pressure (BP), VO2 max, partial oxygen saturation, maximal ventilation (VEmax), stroke volume, rate of lactate removal, HR for a given sub-maximal workload, treadmill endurance time, Cooper 12 minute walk/run <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>, and 1,600 m run time.
<table style="border-collapse: collapse;" border="1">
 <tbody>
 <tr>
 <td>
 More Load Increases Cardiovascular&#xA0;Benefits
 A study by Beckham et al. compared 12 males and 18 females (age: 25.1 &#xB1; 6.6 years) performing a circuit training routine (squats and upper body exercise), for 14 minutes with either light resistance (1.4 kg for males and females) or moderate resistance (5.9 kg for females and 10.5 kg for males). The findings demonstrated that mean VO2, caloric expenditure, and HR were significantly higher for the moderate load condition, and despite achieving the recommended HR, neither condition reached the recommended average VO2 outlined by the American College of Sports Medicine (ACSM) guidelines for cardiorespiratory health (8). This study suggests that increases in load and intensity are also likely to increase the cardiovascular benefits of circuit training; however, circuit training alone may not be ideal for improving cardiovascular health.
 </td>
 </tr>
 </tbody>
</table>

<h4>Specific&#xA0;Adaptations</h4>
Studies comparing circuit training to higher intensity aerobic exercise suggest <a id="specificity" data-tip="1224" target="_blank" href="/glossary-term/specificity" class="glossary">specific</a> adaptation to training should be anticipated. An RCT by Maniazhagu et al. compared 45 healthy boys (age: 15-17 years) randomly assigned to a control group (no additional exercise), a running group, or a circuit training group; exercise was performed for 8 weeks, 5x/week. The running group progressed from 4-6 km at 40% of max HR to 2-3 km at 80% of max HR, and the circuit training group performed 8 stations, 3 sets/exercise, 6-8 reps/set, 7-10 min rest between circuits. The findings demonstrated that the circuit training group improved more on bent knee push-ups, whereas the aerobic training group improved more on the sit-up endurance <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a> (10). An RCT by Gettman et al. compared 41 adult men randomly assigned to a control group (no exercise), a circuit resistance training group, or a running group. The circuit training routine included 10 exercises, performed for 20 weeks, 3x/week, 2 circuits/session, 15 reps (performed in 30 sec)/set, 42-56% of 1-RM loads, 20-25 sec rest between exercises, and the running group ran on a treadmill at 85% max HR for 23 - 27 min/workout. When compared to controls, circuit training significantly improved strength and body fat %, but did not improve VO2max, and the running group significantly improved running performance and VO2max, but did not improve strength (11). Kass et al. compared 14 sedentary healthy men (age: 20 - 40 years) randomly assigned to cycling or circuit training for 10 weeks, 4x/week. Cycling included 30 min/session at 80% of max HR, and circuit training included 1 circuit/session with 8-12 RM/set, for 14 exercises (hip and back extensions, leg extensions, leg press, leg curls, calf raises, pull overs, pull downs, arm cross, decline press, <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> raises, overhead press, bicep curls, triceps extensions, abdominals). The findings demonstrated that the cycling group exhibited a significant increase in VO2max, and the circuit training group did not; however, the circuit training group exhibited a significant increase in upper body strength (12). These studies imply the outcomes we may expect when considering the principle of &quot;Specific Adaptations to Imposed Demands (SAID)&quot;. In summary, circuit resistance training is likely to result in improvements in strength but may not influence VO2 max, and moderate to high-intensity aerobic exercise is likely to result in significant improvements in VO2 max but may not influence strength.
<h4>Cross-over</h4>
Two additional studies suggest that adaptations to circuit training and aerobic exercise are <a id="specificity" data-tip="1224" target="_blank" href="/glossary-term/specificity" class="glossary">specific</a>, but some benefits for strength and aerobic activity may be attained from either strength or aerobic exercise. Moghadasi et al. compared 29 healthy and sedentary men (age: 21-29 years) randomly assigned to aerobic or circuit training groups for 8 weeks, 3x/week. Endurance training (continuous running) was performed for 34 minutes, at 65&#x2013;80% of max HR. Circuit resistance training included 8 stations (chest press, leg extensions, shoulder press, leg curls, latissimus pull-downs, leg press, arm curls, and triceps extensions), 2-4 sets/exercise, 8-12 reps/set, 65-80% of 1-RM loads, 90 sec rest between sets, and 3 min rest between circuits. The findings demonstrated no significant difference in body fat or circumference measurements, VO2 max improved for both groups but more for the endurance training group, and loads lifted increased for the strength training group (13). Birkett et al. compared 39 healthy middle-aged participants (age: 42.5&#x2009;&#xB1;&#x2009;12.3 years) randomly assigned to a high-intensity anaerobic interval training (HIIT) group, or a circuit resistance training group, for 8 weeks, 2x/week. The HIIT program included 8-12 sets, 1 min/set,&#x2009;&gt;&#x2009;85% max HR, 1 min active recovery between sets; and circuit training (cycle ergometer, rower, treadmill, sit to stand/squats, knee to elbow and leg kickback with bicep curl) included 3-6 min/exercise, intensity of 60&#x2013;80% max HR, body weight resistance, and minimal rest between stations. The findings demonstrated that both groups exhibited improvements in cardiorespiratory fitness; however, the HIIT group exhibited significantly larger improvements in VO2 max and anaerobic threshold (14). These studies suggest sedentary individuals performing circuit resistance training may initially attain strength and aerobic benefits; however, larger aerobic performance improvements may be attained from aerobic activity. Further, when circuit and aerobic training programs are combined, benefits may be seen for strength and aerobic performance.

<h4>Single Session</h4>
The best research comparing the cardiovascular benefits of aerobic and circuit training exercise is likely attained from work-matched routines. Gotshalk et al. compared 11 men performing sub-maximal treadmill running, maximal treadmill running, and circuit resistance training. Circuit resistance training included 10 exercises, 4.6 circuits/session, 10 reps/exercise, and 40% of 1-RM loads. The findings demonstrated that circuit training resulted in more than 70% of max HR maintained for the last 16.6 min, and 80% of max HR with 50% of VO2 max for the last 12 minutes. Comparatively, treadmill running resulted in a quicker increase to 50% of VO2 max with a lower HR (15). Brewer et al. compared 9 resistance and aerobic trained college-aged men performing circuit training and aerobic activity. The circuit training included 10 exercises (chest press, leg press, lat pull-downs, shoulder press, leg curls, leg extensions, assisted pull-ups, pectoral flyes, seated rows, back extensions), for 15 reps/set, with 40% of 1-RM, and took 20 minutes to complete, and the aerobic training included a 20 minute treadmill session with the same average HR achieved during circuit training. The findings demonstrated that circuit training resulted in an average of 61% of HR reserve. When compared to the same intensity and session length on a treadmill, circuit training resulted in less calories burned, a lower respiratory rate, and a higher rate of perceived exertion (RPE) (16). Braun et al. compared 8 healthy women (age: 31.3 &#xB1; 9.1 years) performing circuit training and treadmill exercise during separate sessions. The circuit training consisted of 8 common exercises, 3 sets/exercise (circuits per session), 15 reps/set, 65% of 1-RM, 30 sec rest between exercises, with 2 min rest between circuits, and the treadmill exercise was matched for time and O2 consumption. The findings demonstrated that respiratory exchange ratio (RER), HR, ventilation rate, and RPE were higher for circuit training. Further, excess post-exercise oxygen consumption (EPOC) was higher during the first 35 minutes following circuit training, higher during the second 25 minutes following aerobic exercise, but total EPOC was similar for both at 60 minutes (17). Armas et al. compared 6 males and 6 females (age: 20 - 35 years) performing 7 minutes of circuit training and 7 minutes of high-intensity interval training (HIIT) training on a cycle ergometer. The circuit training consisted of 12 exercises (jumping jacks, wall sits, push-ups, abdominal crunches, step ups (on 16-in step), squats, triceps dips on step, planks (high or low), high knees, lunges, push-up with rotation (one hand points towards ceiling after up phase of push up and returns to the mat), and side planks), for 1 circuit/session (7 minutes), 30 sec/exercise, 5 sec rest between exercise, and tempo/rep dictated by a metronome. The HIIT group performed a similar pattern on a cycle ergometer, including 12 sets, 30 sec/set, 5 sec rest between sets, 70 RPM, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> output adjusted to achieve 70 - 80% of max HR. The findings demonstrated that both protocols resulted in similar decreases in post-exercise serum blood glucose and blood triglycerides; however, circuit training resulted in a larger post-exercise decrease in diastolic blood pressure (18). These studies demonstrate that work-matched circuit resistance training and aerobic activity may result in similar peak HR, O2 consumption, EPOC, blood glucose, and triglycerides. However, aerobic activity performed with the same O2 consumption as a circuit training routine results in a lower HR, ventilation rate, and rate of perceived exertion (RPE), and aerobic activity with a similar HR as circuit training burns more calories.
<h4>Comparing Outcomes Following Weeks of Training</h4>
Additional studies compare the outcomes from work-matched aerobic activity and circuit resistance training following several weeks of training. An RCT by Camargo et al. compared 20 healthy male subjects (age: 30 &#xB1; 4 years) randomly assigned to a control group (no additional activity), aerobic training group, or a circuit training group. The exercise groups trained for 12 weeks, 36 sessions total, 3x/week, and 35 min/session. The circuit training included abdominal, upper body, and lower body exercise, 3 circuits/session, 15 reps/set, 60% of 1-RM, moderate (3 sec/rep) tempo, as little rest as possible between exercises, and the intent to maintain 70% of max HR. The aerobic training was performed on a treadmill with a 5 min warm-up period, running at 70% of max HR, and a 5 min cooldown. The findings demonstrated similar decreases in body fat % and increases in lower body strength, circuit training exhibited <a id="superior" data-tip="1570" target="_blank" href="/glossary-term/superior" class="glossary">superior</a> improvements for upper body strength and increased lean body mass, both groups demonstrated similar improvements in VO2 max, and MRI demonstrated no significant changes in left ventricular mass, left ventricular volumes or ejection fraction after the interventions (19). An RCT by Kaikkonen et al. compared 90 healthy adults (45 men, 45 women, age: 42.0 &#xB1; 7) divided into control (no additional activity), circuit weight training, and aerobic training groups; both exercise groups trained for 12 weeks, 3x/week. The circuit training included 10 air resistance machines, 3 sets/exercises, 20 sec rest between sets, 40 sec/exercise, and was designed to maintain 70-80% of HR max for approximately 30 min, in addition to a 5 min warm-up and 5 min cool down. The aerobic training (jogging) was performed for 40 min with the same HR as the circuit group. The findings demonstrated that both groups exhibited significant improvements when compared to controls, both groups exhibited similar improvements of VO2 max, and the circuit weight training group exhibited larger improvements for abdominal and arm strength endurance tests (20). These studies demonstrate that circuit resistance training is likely <a id="superior" data-tip="1570" target="_blank" href="/glossary-term/superior" class="glossary">superior</a> for strength improvements when compared to aerobic training. Further, increases in cardiovascular performance are likely similar when comparing circuit training and aerobic activity with the intensity matched by average % of max HR. However, it should be noted that matching circuit training and aerobic exercise by % of max HR likely limits aerobic activity intensity to the average HR that can be achieved during circuit training. It is likely that if aerobic exercise is matched to circuit training by RPE, the result would be a higher % of max HR and larger improvements in cardiovascular performance achieved from aerobic activity.

Additional studies have compared the effects of combining aerobic exercise and resistance training during the same session. Myers et al. compared 34 sedentary females (age: 20.9 &#xB1; 3.2 years) randomly assigned to a combined aerobic and resistance training circuit, or a conventional resistance training routine followed by aerobic exercise. Both programs were performed for 5 weeks, 3x/week, 3 sets/exercise, 10-15 reps/set, and were modified weekly. An example of an aerobic circuit included squats, push-ups, lunges, planks, sprints, mountain climbers, and leg drops, with a focus on exercises that could be performed without equipment, and with as little rest as possible between exercises. An example of a conventional resistance training circuit followed by aerobic activity included machine chest press, machine leg press, wide-grip lat pull-downs, machine leg extensions, machine shoulder press, machine hamstring curls, seated crunches on ball, with each exercise performed with 50-70% of 1-RM loads, short (1 min) rest between sets, and followed by 15 min of aerobic exercise at 80% of max HR. The findings demonstrated that the aerobic circuit group exhibited larger improvements for VO2 max, the conventional group exhibited larger improvements for strength, and both groups improved similarly for muscular endurance and Wingate <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a> performance (anaerobic threshold) (21). Two RCTs published by Chtara et al. (2005, 2008) compared 48 physical-education students (age: 21.4 &#xB1; 1.3 years) divided into 5 groups: controls (no training), run training, circuit training, run before circuit training in the same session, and circuit before run training in the same session. Resistance training included strength endurance training for 6 weeks followed by <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training for 6 weeks. Aerobic training sessions included 5 reps of running at approximately 50% of VO2 max for half the duration to exhaustion, followed by equal rest. The findings demonstrated that running before circuit training resulted in the largest improvements in a 4km time <a id="randomized-control-trial" data-tip="1407" target="_blank" href="/glossary-term/randomized-control-trial" class="glossary">trial</a> when compared to circuit training before running, and circuit training or running alone. Further, there was no significant difference in strength for the two run and circuit training groups; however, the resistance-only group exhibited <a id="superior" data-tip="1570" target="_blank" href="/glossary-term/superior" class="glossary">superior</a> improvements in 1RM strength and jump <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a> performance (22, 23). An RCT by Gettman et al. (1982) compared 36 females (mean age = 35.7 yr) and 41 males (mean age = 36.1 yr) randomly assigned to a control group (no exercise), circuit resistance training group, or circuit training with a 30 sec running station group. The circuit training routine included 10 exercises, with and without 30 seconds of running in between exercises, for 12 weeks, 3x/week, 3 circuits/session, 12-15 reps (performed in 30 sec)/set, 40% of 1-RM loads, and 15 sec rest between exercises for the group not running between stations. When compared to controls, the circuit training groups, with and without 30 sec of running, exhibited improvements in VO2 max, strength, and body fat; however, differences between groups did not reach statistical significance (24). Gettman et al. compared 16 individuals (mean age: 29 yrs) performing 8 weeks of circuit training, followed by 8 weeks of aerobic training, followed by 8 weeks of aerobic or circuit training. The circuit training included reciprocal isokinetic machines, performed for 8 weeks, 3x/week, 2 circuits/session, 10-15 reps/set, 30 sec rest between exercises, and the aerobic program included treadmill jogging/running for 8 weeks, 3x/week, 3 miles/day. The findings demonstrated that 8 weeks of circuit training resulted in significant improvements in treadmill performance time, VO2 max, maximum pulmonary ventilation (VEmax), body fat, lean body mass, circumference measurements, isotonic bench and leg press endurance, and strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> at slow and fast isokinetic machine speeds. The jogging program resulted in significantly larger changes in treadmill performance time, VO2max, additional reductions in body fat and waist circumference, maintenance of leg strength, but a loss of upper body strength. During the final 8 weeks, both groups exhibited similar maintenance of performance without statistically significant improvements (25). These studies suggest improvements in performance are likely similar when combining aerobic training and resistance training into the same circuit, same session, or sequentially in the same program. However, it may be <a id="optimal" data-tip="1571" target="_blank" href="/glossary-term/optimal" class="glossary">optimal</a> for aerobic performance to perform aerobic activity prior to resistance training and may be <a id="optimal" data-tip="1571" target="_blank" href="/glossary-term/optimal" class="glossary">optimal</a> for maximal strength to perform strength training alone (without aerobic activity in the same session).
<img title="Running/jogging as a form of cardiorespiratory fitness" src="https://www.datocms-assets.com/25800/1649652884-running.jpg" width="442" height="353" alt="Cardiorespiratory fitness activity">

Physiology

Studies have demonstrated that circuit training may have a significant effect on blood glucose and lipid profiles. An RCT by Beqa Ahmeti et al. compared 57 women (age: 23 &#xB1; 3 years) randomly assigned to a control group (no additional activity), aerobic exercise group, or circuit resistance training group. Exercise was performed for 8 weeks, 3x/week, 45-60 min/session. The aerobic training group walked, jogged, or ran on a treadmill with the ability to incline, HR of 120-155 beats/min (60-80% max HR), using a variety of steady state, interval, and Fartlek routines of their choosing. The strength training group performed a circuit of 10 exercises (example: crunches, leg raises, hyperextensions, knee extensions, leg curls, lunges, squats, lat pull downs, bench press, bicep curls, triceps extensions) for 2-3 circuits/session, 30 sec/set, 30 sec rest between exercises, and 2 min rest between circuits. The findings demonstrated that both exercise groups exhibited significant and similar improvements in blood glucose, lipid profiles, BMI, and circumference measurements (26). As mentioned above, Armas et al. compared 6 males and 6 females (age: 20 - 35 years) performing 7 min of circuit training, or 7 min of high-intensity interval training (HIIT) on a cycle ergometer. The findings demonstrated that both protocols resulted in similar decreases in post-exercise serum blood glucose and blood triglycerides; however, circuit training resulted in a larger post-exercise decrease in diastolic blood pressure (18). Also mentioned above, Kim et al. compared 20 obese (30% of accumulated body fat) female college students (age: circuit 22.90&#xB1; 2.23, control 24.50&#xB1; 1.72 age) randomly assigned to a control group (no additional activity), or a circuit training group for 12 weeks, 3x/week. The findings demonstrated that circuit training resulted in significant improvements of post-exercise serum triglycerides and total cholesterol; however, no improvements were demonstrated for blood glucose and high-density lipoprotein (HDL)/low-density lipoprotein (LDL) ratio (4). These studies suggest that resistance training, including circuit training, can have a significant effect on triglycerides, total cholesterol, and potentially glucose; however, circuit training may have little effect on HDL/LDL ratio. Further, some, or all of these benefits may be achieved with as little as 7 minutes of circuit training/day.

These studies investigate blood/serum concentrations of metabolic markers that are not commonly introduced to movement professionals. The following is a brief summary of the markers mentioned, and the implications they may have on health and wellness:
<ul>
 <li>Insulin Resistance Index is a formula used primarily by researchers to aid in assessing the potential of diabetes in a non-diabetic population (HOMA-IR = fasting insulin (microU/L) x fasting glucose (nmol/L)/22.5.</li>
 <li>C-reactive Protein is a marker of inflammation that has been correlated with coronary artery disease risk.</li>
 <li>Irisin is a myokine secreted by muscles that may have an influence on weight loss and thermoregulation.</li>
 <li>Chemerin is an adipokine, and dysregulated production has been correlated with obesity and metabolic disorders.</li>
 <li>Serum amyloid A is a&#xA0;highly conserved, acute-phase protein synthesized predominantly by the liver. Levels of this protein may increase by 1000 fold with acute inflammation, and their function has an effect on high-density lipoproteins.</li>
 <li>Lipocalin-2 (Lcn2) and Apelin have been recognized as bioactive mediators <a id="release" data-tip="1253" target="_blank" href="/glossary-term/release" class="glossary">released</a> by <a id="connective-tissue-cell" data-tip="1776" target="_blank" href="/glossary-term/connective-tissue-cell" class="glossary">adipose tissue</a>, and the elevation of these mediators has been correlated with some of the negative effects of inflammation and obesity.</li>
 <li>Ghrelin and Obestatin are gut/brain <a id="hormone" data-tip="1268" target="_blank" href="/glossary-term/hormone" class="glossary">hormones</a> that play a role in signaling satiety (feeling full), and lower concentrations and a lower ghrelin/obestatin ratio may be correlated with obesity.</li>
</ul>
Several studies have investigated the effects of circuit training on markers of metabolic function. Rioux et al. compared inactive overweight (BMI &#x2265; 25 kg/m2) participants, 15 adults (age: 19-35, 25.9 &#xB1; 5.0 years) and 14 older adults (age: 60-75, 67.7 &#xB1; 4.1 years), performing a 6 exercise circuit (incline dumbbell press, lat pull-downs, bicep curls, 3 min box-step, 3 min squats, 1 min plank), 3 circuits, 12-15 reps/set, 65-70% of 1 RM, 55 sec rest between exercises, with a blood draw between each circuit. The findings demonstrated that serum irisin concentrations were not significantly altered between circuits or following the session, and were similar for all individuals regardless of age, gender, or body composition (27). Kolahdouzi et al. compared 30 obese men (age: 23 &#xB1; 3.2 years) divided into control (no additional exercise) and circuit training groups. The circuit training group performed a resistance training circuit (eight exercises: squat, standing curls, bench press, leg extension, leg flexion, leg press, military press, and lat pull downs) for 4 weeks, 3x/week, 2 circuits/session, 8-12 reps/set, 65 - 75% of 1-RM, with 15 sec rest between exercises; followed by a <a id="exercise-progression" data-tip="1184" target="_blank" href="/glossary-term/exercise-progression" class="glossary">progression</a> of the same routine for 4 more weeks, including 4 circuits/session, 6-8 reps/set, and 75 - 85% of 1-RM. The findings demonstrated that compared to controls, circuit training had a significant positive effect on serum concentrations of chemerin, serum amyloid A, insulin (insulin resistance index), total cholesterol, triglycerides, low-density lipoproteins (LDLs), and high-density lipoproteins (HDLs). Note, the circuit training group did not exhibit a significant change in apelin or c-reactive protein levels (28). Moghadasi et al. compared 29 healthy and sedentary men (age: 21-29 years) randomly assigned to aerobic or circuit training groups, for 8 weeks, 3x/week. Endurance training (continuous running) was performed for 34 minutes, at 65&#x2013;80% of max HR. Circuit resistance training included 8 stations (chest press, leg extensions, shoulder press, leg curls, latissimus pull-downs, leg press, arm curls, and triceps extensions), 2-4 sets/exercise, 8-12 reps/set, 65-80% of 1-RM loads, 90 sec rest between sets, and 3 min rest between circuits. Findings demonstrated no significant difference in body fat or circumference measurements, VO2 max improved for both groups but more for the endurance training group, and loads lifted increased for the strength training group. Lipocalin-2 decreased for both groups; however, significant improvements were not exhibited for insulin resistance or high <a id="sensitivity" data-tip="1226" target="_blank" href="/glossary-term/sensitivity" class="glossary">sensitivity</a> C-reactive protein (13). Hedayati et al. compared 27 female students (age: 22 &#xB1; 1.54 years) randomly assigned to circuit training groups using loads of 40% or 80% of 1-RM. Circuit training including 9 exercises (chest press, leg press, seated rows, overhead press, knee extensions, triceps extensions, leg curls, arm curls, and heel raises) for 4 weeks, 4x/week, 3 circuits/session, 30 sec (8-11) reps/set, 30 sec rest between exercises, and 2 min rest between circuits. Each session lasted about 50-55 minutes, including a 20 min light aerobic warm-up, 30 min of circuit training, and a 5 min cool-down. The findings demonstrated that circuit training significantly decreased plasma concentrations of obestatin, increased the ghrelin/obestatin ratio, but did not have a significant effect on ghrelin or glucose concentrations. Further, training with loads of 80% of 1-RM may have a larger effect on obestatin than 40% of 1-RM training (29). In summary, these studies demonstrate that circuit training may have a positive effect on some, but not all markers of metabolic function. Positive effects were noted for serum concentrations of chemerin, serum amyloid A, insulin (insulin resistance index), Lipocalin-2, obestatin, and the ghrelin/obestatin ratio. However, no significant effects were noted for insulin <a id="sensitivity" data-tip="1226" target="_blank" href="/glossary-term/sensitivity" class="glossary">sensitivity</a>, or serum concentrations of glucose, irisin, apelin, ghrelin, or c-reactive protein (including high-sensitivity c-reactive protein testing).

Two studies by Ibrahim et al. have investigated how the immune system is affected by circuit training and probiotic supplementation. An RCT by Ibrahim et al. (2017) compared 41 healthy sedentary males randomly assigned to 4 groups: no exercise and placebo supplement, no exercise and probiotic supplement, circuit training and placebo supplement, and circuit training and probiotic supplement. Circuit training included 10 exercises, performed for 12 weeks, 3x/week, 1:2 work:rest ratio, and the supplement was either a multi-strain probiotic or placebo taken for 12 weeks, 2x/day.&#xA0; The findings demonstrated that neither exercise or probiotic supplement had a significant effect on immune system function including concentrations of salivary IgA, &#x3B1;-amylase, lactoferrin, total leukocytes, total lymphocytes, T lymphocytes, T-helper, T-cytotoxic, B lymphocytes, and natural killer cell counts (30). Another similar RCT by Ibrahim et al. (2018) compared 48 young males randomly assigned to 4 groups: no exercise and placebo, no exercise and probiotic, circuit training and placebo, or circuit training and probiotic. The circuit training was performed for 12 weeks, 3x/week, with weeks 1-8 completing 2 circuits/session, and weeks 9-12 completing 3 circuits/session. Additionally, either a multi-strain probiotic or a placebo was taken during the same 12 weeks, 2x/day. The findings demonstrated that the circuit training groups exhibited significant increases in knee extension strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>. Neither group exhibited altered serum IL-6 concentrations, both probiotics alone and circuit training alone resulted in significantly higher concentrations of serum IL-10 concentrations; however, elevations of IL-10 did not reach statistical significance when probiotics and circuit training were combined (31). These studies suggest that circuit training, with or without probiotic supplementation, is unlikely to have a significant short-term effect on immune function, based on post-exercise concentrations of salivary IgA, &#x3B1;-amylase, lactoferrin, total leukocytes, total lymphocytes, T-lymphocytes, T-helper, T-cytotoxic, B lymphocytes, and natural killer cells counts. The one potential exception is IL-10 concentrations.

Studies have investigated the influence of circuit training on various growth <a id="hormone" data-tip="1268" target="_blank" href="/glossary-term/hormone" class="glossary">hormones</a>. Moghadasi et al. compared 20 sedentary females (age: 25.3 &#xB1; 3.2 years) randomly assigned to a control group (no additional activity) or a circuit training routine of 8 exercises (chest press, leg extensions, shoulder press, leg curls, latissimus pull-downs, leg press, arm curls, and triceps extensions) for 12 weeks, 3x/week, 8-12 reps/set, 65-80% of 1-RM loads, and 50-60 min/session. The circuit training group exhibited significant increases in <a id="hormone" data-tip="1268" target="_blank" href="/glossary-term/hormone" class="glossary">hormones</a> associated with bone growth, including growth <a id="hormone" data-tip="1266" target="_blank" href="/glossary-term/hormone" class="glossary">hormone</a>, estrogen, parathyroid <a id="hormone" data-tip="1266" target="_blank" href="/glossary-term/hormone" class="glossary">hormone</a>, and testosterone; however, IGF-1 did not increase (32). Valipour Dehnou et al. compared 10 elderly men and women (age: 64.40 &#xB1; 6.69 years) performing a circuit of body weight resistance exercises (push-ups, squats, triceps dips, planks, and side planks) and fast walking (aerobic training). The circuit routine included 3 sets/exercise, (15 reps, 30 reps, or 30 sec)/exercise, 120 m of jogging between sets, and 3 min rest between exercises. The findings demonstrated that post-exercise serum levels of brain-derived neurotrophic factor (BDNF) increased and insulin-like growth factor-1 (IGF-1) decreased; however, the increase in BDNF was not statistically significant for elderly men (33). Harber et al. compared 12 men (age: 18 - 35 years) randomly assigned to a control group (no exercise), or a timed circuit training program. The circuit training program included 10 Nautilus and Hammer Strength machine exercises (chest press, chest flyes, lat pull-downs, shoulder presses, seated rows, biceps curls, triceps extensions, leg press, leg extension, and leg curls) performed for 10 weeks, 3x/week, 1-3 circuits/session, 20-30 sec (8 - 20 reps)/set, 10-30 sec rest between exercises, and 40 - 60% of 1-RM loads. Findings demonstrated that circuit training resulted in a trend toward improvements in circumference, body fat %, and fat free mass, but the effect size did not reach statistical significance. <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">Muscle</a> biopsy demonstrated an increase in type IIa fiber cross-sectional area, an increase in the percentage of MHC IIa, and a decrease in the percentage of MHC IIb. Post-exercise blood samples taken after the first and last session demonstrate an improvement in the accumulation of lactate, and no change in concentrations of testosterone, cortisol, or testosterone/cortisol ratio (34). In summary, these studies investigate 3 very different groups of participants (women, young men, and elderly individuals), and suggest that circuit training may have a significant influence on some, but not all <a id="hormone" data-tip="1268" target="_blank" href="/glossary-term/hormone" class="glossary">hormones</a> associated with bone growth, <a id="hypertophy" data-tip="1233" target="_blank" href="/glossary-term/hypertophy" class="glossary">muscle growth</a>, and cognition. This includes increases in post-exercise serum concentration of growth <a id="hormone" data-tip="1266" target="_blank" href="/glossary-term/hormone" class="glossary">hormone</a>, estrogen, and parathyroid <a id="hormone" data-tip="1266" target="_blank" href="/glossary-term/hormone" class="glossary">hormone</a>, but no change in concentrations of IGF-1, and inconsistent changes in concentration of brain-derived neurotrophic factor (BDNF), testosterone, cortisol, or testosterone/cortisol ratio.

Caloric Expenditure

Caloric expenditure during circuit training has been investigated with a variety of populations and study designs. As mentioned above, Wilmore et al. compared 49 men and women (age: 17 - 36 years), randomly assigned to a control group (no additional activity) or a circuit training group for 10 weeks, 3x/week, for 22.5 minutes/session. The findings demonstrated that caloric consumption was highly correlated with body weight (7.0 and 6.0 kcal/kg-hr), and men and women were nearly identical when caloric consumption was correlated with lean body weight (LBW) (8.1 and 8.2 kcal/kg (LBW)-hour) (35). Beckham et al. compared 12 males&#xA0;and 18 females (age: 25.1 &#xB1; 6.6 years) performing a circuit training routine (squats and upper body exercises) for 14 minutes with either light resistance (1.4 kg for males and females) or moderate resistance (5.9 kg for females and 10.5 kg for males). The findings demonstrated that average VO2 consumption, caloric expenditure, and HR were significantly higher for the moderate load condition (8). These studies suggest that&#xA0;men and women burn calories at a similar rate when calculated based on kcal/lean body weight, and significant increases in load result in a significant increase in caloric expenditure.&#xA0;(Note, as discussed below, the difference in caloric expenditure is statistically significant, but relatively small).

Additional studies investigate caloric expenditure when comparing and combining aerobic training and circuit training. Brewer et al. compared 9 trained college-aged men performing both circuit training and aerobic exercise. The circuit training included 10 exercises (chest press, leg press, lat pull-downs, shoulder press, leg curls, leg extensions, assisted pull-ups, pectoral flyes, seated rows, back extensions) for 15 reps/set, with 40% of 1-RM, performed for 20 min, and the aerobic training included a 20 min treadmill session with the same average HR achieved during circuit training. The findings demonstrated that circuit training was performed with an average intensity of 61% of HR reserve, and resulted in less calories burned, a lower respiratory rate, and a higher RPE when compared to aerobic exercise of the same intensity and length (16). Vasconcelos et al. compared 14 trained males (age: 25.7&#x202F; &#xB1; &#x202F;4.4&#x202F; years) completing two exercise protocols including circuit training and high-intensity interval running (HIIT), matched for volume and recovery periods. Both routines included a combination of 6 bouts of HIIT with 15 sec run/set and 45 sec rest between sets (1:3 work: rest ratio), and circuit training including 9 exercises (squats, rows, planks, press, trap bar deadlifts, crunches, sumo squats, lat pull-downs, and lumbar extensions) for 10-15 reps (30 sec)/set, and 30 sec rest between sets (work: rest ratio of 1:1). The first routine started with 6 bouts of HIIT followed by 3 circuits, the second routine performed the 9 exercises as 3 mini-circuits of 3 exercises, 3 sets for each circuit, with the bouts of HIIT between the mini-circuits. The findings demonstrated that the routine starting with 6 bouts of HIIT resulted in higher HR, lactate accumulation, VO2 consumption, energy expenditure, and EPOC; however, the difference between the protocols (combining in-session and EPOC) was only about 20 calories (38). In summary, circuit training burns fewer calories than aerobic training when routines are matched by average HR and session duration; further, HIIT sets before a circuit routine burns slightly more calories than HIIT sets in a circuit routine.

<h4>Comparing Circuit Training and Aerobic Exercise</h4>
Excess post-exercise oxygen consumption (EPOC) following circuit training has been investigated in several research studies. As mentioned above, Vasconcelos et al. compared 14 trained males (age: 25.7&#x202F; &#xB1; &#x202F;4.4&#x202F; years) completing two exercise protocols, including HIIT before circuit training and HIIT interspersed with circuit training. The findings demonstrated that the routine starting with 6 bouts of HIIT resulted in slightly more calories burned (approximately 20 calories) when combining in-session calories and EPOC (38). Braun et al. compared 8 healthy women (age: 31.3 &#xB1; 9.1 years) performing circuit training and treadmill exercise during separate sessions. The circuit training consisted of 8 common exercises, 3 circuits/session, 15 reps/set, 65% of 1-RM, 30 sec rest between exercises, with 2 min rest between circuits, and the treadmill exercise was matched for time and VO2 consumption. The findings demonstrated EPOC was higher during the first 35 minutes post circuit training, higher 35 - 60 minutes post aerobic training, and total EPOC was similar for both protocols 60 minutes post-exercise (17). Elliot et al. compared 9 physically active participants with exercise experience (4 men and 5 women) during a light load circuit training protocol, a heavy load circuit training protocol, and a cycling program. The circuit training exercises were identical for both protocols (bench press, knee extensions, leg curls, seated leg press, lat pull downs, military press, seated rows, and seated machine pec flyes); the light load protocol was performed for 40 min/session, 50% of 1-RM loads, 4 sets/exercise, 15 reps/set, and 1 min rest between sets; and the heavy load protocol was performed for 40 min, 80-90% of 1-RM loads, 3 sets/exercise, 3-8 reps/sets, and 1 - 2 min rest between sets. The cycling protocol included 40 min at 80% of max HR. The findings demonstrated that an increase in load during circuit training resulted in a small increase in EPOC, and both circuit training protocols resulted in more EPOC than cycling (39). These studies suggest that heavy circuit training may result in more calories burned than light circuit training, and circuit training may result in more EPOC than aerobic exercise; however, the differences in calories burned are small (approximately 20 total calories).
<img src="https://www.datocms-assets.com/25800/1661747092-epoc-compressed.jpg" width="519" height="390" title="Image of the effect circuit training has on Excess Post-Exercise Oxygen Consumption" alt="A graph showing the effects of EPOC">
<h4>Comparing Circuit Training and Conventional Resistance Training (as well as different loads and volumes)</h4>
Additional studies have compared EPOC following circuit training and conventional resistance training, with different loads and volumes. As mentioned above, Elliot et al. compared 9 physically active participants with exercise experience (4 men and 5 women) with indirect calorimetry performing 40 minutes of circuit training, 40 minutes of heavy resistance training, or 40 minutes of cycling (80% of max HR). The findings demonstrated that EPOC was similar for circuit training and heavy resistance training, which was slightly higher than cycling (39). Murphy et al. compared 10 untrained men (age: 23.6 &#xB1; 3.9 years) performing circuit resistance training or conventional resistance training protocols. Both routines included the same exercises (<a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> cleans, bench press, squats, bicep curls, seated military press, and bent knee sit-ups), the resistance training protocol included 3 sets/exercise, (12, 10, 8 reps)/set, 80% of 1-RM loads, moderate (2 min) rest between sets, and took 50 minutes to complete. The circuit training protocol included 3 sets/exercise performed in circuit, reps until failure/set, 50% of 1-RM, 30 sec rest between exercises, and took 19 minutes. The findings demonstrated that EPOC lasted for approximately 20 minutes and burned an additional 24.9 calories following the circuit training protocol, and lasted approximately 15 minutes and burned 13.9 calories following the conventional resistance training routine (40). Haltom et al. compared 8 resistance-trained men (aged 22 &#xB1; 3 years) performing 10,000 kg or 20,000 kg in total load lifted (volume) during circuit resistance training with loads divided between 4 exercises: 35% squats, 30% bench press, 20% bent-over rows, and 15% Romanian deadlifts, 6-8 reps/set with 85% of 1-RM loads. The findings demonstrated that the post-exercise in calories was similar following both routines (41). These studies suggest that EPOC is similar following circuit training and conventional resistance training, even when loads and volumes are very different. Although circuit training (when compared to conventional training), heavier loads, and larger volumes of exercise may increase EPOC and caloric expenditure, the difference in calories burned is 10 - 20 calories/session.

Circuit training may have a beneficial effect on body image, even when changes in circumference measurements, weight, and body fat are not statistically significant. Plevkova et al. compared 53 primary school girls (age: 14-15 years) randomly assigned to a control group (no additional activity), a circuit training and objective measure group, and a circuit training and body satisfaction measure group. Both exercise groups performed circuit resistance training, including 6-12 exercises (variations of squats, push ups, lunges, sit ups, <a id="stability" data-tip="1191" target="_blank" href="/glossary-term/stability" class="glossary">stability</a> ball exercises, etc.), for 6 weeks, 2x/week, 2-3 circuits/session, 30 sec/set, 15 sec rest between exercises, 2 min rest between circuits, and sessions lasting 20 - 35 minutes. The findings demonstrated that the objective measure group did not exhibit significant changes in BMI or body weight; however, the body satisfaction group exhibited a significant decrease (improvement) in the discrepancy between perceived current body image and ideal body image (42). Plevkova et al. repeated this study with teenage girls (age: 16.99 &#xB1; 0.29 years) demonstrating the same findings (43). Williams et al. compared 39 college students (27 women and 12 men) participating in a circuit weight training class, and 39 controls matched by gender, age, race, BMI, and level of previous and concurrent aerobic exercise. The findings demonstrated that circuit training resulted in significant improvements in strength, self-evaluation of appearance, body satisfaction, reduced social physique anxiety, and enhanced physical self-efficacy (44). Rahmani-Nia et al. compared 40 male college students randomly assigned to a control group (no additional activity), or a circuit training group. The circuit training program included progressive load/volume resistance training performed for 8 weeks, 3x/week. At the end of the 8-week program, the findings demonstrated no significant change in BMI, circumference measurements, or body fat percentage; however, significant improvements were demonstrated for upper and lower body 1-RM strength, perception of body image, and reduced social physique anxiety (45). Last, Norvell et al. compared 43 male state law enforcement officers (age: 20-47 years) who were not regularly exercising when enrolled in the study. Participants were randomly assigned to a waitlist control group or a circuit training group. Circuit training included 12 Nautilus machines (duo hip and back, leg extensions, leg curls, leg press, pullovers, torso arm pulldowns, arm cross, decline press, <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> raises, overhead press, bicep curls, and triceps extensions) performed for 16 weeks, 3x/week, 20 minutes/session, 8-12 reps/set, 8-12 RM loads, and a slow (4:0:2) tempo. The findings demonstrated that the circuit training group exhibited a significant increase in strength and cardiovascular performance; as well as improvements in mood, including decreases in somatization, anxiety, depression, hostility, a decrease in physical symptoms, and improvements in job satisfaction. Note, that participants who dropped out of the circuit training program exhibited significantly higher levels of anxiety, depression, and hostility before the study started (46). These studies demonstrate that even when circuit training has yet to result in statistically significant improvements in circumference measurements, body fat, or weight measures; significant improvements in body image may be achieved. These changes may include a decrease in the discrepancy between perceived current body image and ideal body image, self-evaluation of appearance, body satisfaction, social physique anxiety, and physical self-efficacy. Additionally, circuit training may result in significant improvements in mood, including decreases in somatization, anxiety, depression, hostility, and job satisfaction. Further, it is worth noting that the studies demonstrating these findings included a wide variety of participants from 14 - 47 years old, students, professionals, active individuals, and previously sedentary individuals.

Body Composition (Body Fat Percentage, Lean Body Mass, and Circumference Measurements)

<h4>No Change in Body Composition</h4>
Several studies have investigated the effects of circuit training on body composition (body fat %, lean body mass, total fat). Moghadasi et al. compared 29 healthy and sedentary men (age: 21-29 years) randomly assigned to aerobic or circuit training groups, for 8 weeks, 3x/week. Aerobic training (continuous running) was performed for 34 minutes, at 65&#x2013;80% of max HR. Circuit resistance training included 8 stations (chest press, leg extensions, shoulder press, leg curls, latissimus pull-downs, leg press, arm curls, and triceps extensions), 2-4 sets/exercise, 8-12 reps/set, 65-80% of 1-RM loads, 90 sec rest between sets, 3 min rest between circuits. Findings demonstrated no significant change in body fat % or circumference measurements, VO2 max improved for both groups but more for the endurance training group, and loads lifted increased for the strength training group (13). As mentioned above, Rahmani-Nia et al. compared 40 male college students randomly assigned to control (no additional activity) and circuit training groups. The circuit training program progressed in load and volume for 8 weeks, 3x/week. At the end of the 8-week program, there were no significant changes in body mass index (BMI), circumference measurements, or body fat %; however, significant improvements were demonstrated for upper and lower body strength (45). These studies suggest that circuit training for 8 weeks, 2-4 circuits/session, with moderate resistance, may be insufficient to significantly alter body composition, despite significant improvements in strength and cardiovascular performance.
<h4>No Change in Body Composition following Circuit Training with Hydraulic and Isokinetic Equipment</h4>
Additional studies demonstrate that circuit training with hydraulic or isokinetic equipment may be particularly ineffective. Lehnert et al. compared 9 untrained women (age: 36.2 &#xB1; 9.97 years) performing a 16 exercise circuit of alternating isokinetic equipment (concentric resistance only) and bodyweight exercises performed for 12 weeks, 3x/week, 4 circuits/session, 30 sec/set, 5 sec rest between exercises, 10 min/circuit, and 40 min/session. The study demonstrated that changes in lean body mass, body fat %, and body weight were insignificant, only small increases in the total number of reps and peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> were observed, and the isokinetic equipment made determining changes in intensity difficult to monitor (47). An RCT by Hortobagyi et al. compared 28 college males randomly assigned to control (no additional activity), low-resistance, and high-resistance training groups. Circuit training was performed for 13 weeks, 3x/week, on hydraulic resistive exercise equipment (7 upper and lower body, and 6 supplementary), 2 circuits/session, 20 sec/set, 40 sec rest between exercises, low resistance was set at a tempo of 100 cm/sec, high resistance was set at 50 cm/sec, sessions lasted about 40 min, and were followed by running for 2 miles. The findings demonstrated that the exercise groups did not exhibit significant changes in body fat% or circumference measurements, and both groups exhibited relatively small improvements in <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> strength, <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> endurance, and run performance (48). These studies demonstrate that circuit training with hydraulic or isokinetic equipment, for 12- 13 weeks, is unlikely to result in improvements in body composition or circumference measurements. Additionally, circuit training with this equipment may result in relatively small improvements in strength.

<h4>Trending Toward Body Fat Percentage Improvements:</h4>
In two studies mentioned above, circuit training resulted in trends toward improvements in body composition. Wilmore et al. compared 49 men and women, randomly assigned to a control group (no additional activity) or a circuit training group, for 10 weeks, 3x/week. The findings demonstrated significant improvements in lean body weight and flexed bicep circumference. Further, skinfold measurements significantly improved, despite a lack of significant change in body weight or absolute fat weight (7). Harber et al. compared 12 men (age: 18 - 35 years) randomly assigned to a control group (no exercise), or a timed circuit training program for 10 weeks, 3x/week. The findings demonstrated that circuit training resulted in a trend toward improvements in circumference measurements, body fat %, and fat-free mass; however, the effect size did not reach statistical significance (34). Although these studies failed to demonstrate clear evidence of body fat % improvements, the trends toward improvement, and the significant improvements of related outcome measures (skinfold, circumference, and lean body weight measurements), suggest that circuit training (10 weeks, 3x/week) has the potential to improve body composition.
<img src="https://www.datocms-assets.com/25800/1661924050-body_fat_caliper-compressed.png" width="176" height="255" title="Skinfold calipers are one method which individuals use to measure body fat percentages" alt="Skinfold caliper used to measure body fat">
<h4>Significant Changes in Body Fat Percentage</h4>
Conversely, many studies demonstrate a correlation between circuit training and changes in body composition. An RCT by Batrakoulis et al. compared 49 healthy overweight females (age: 36.4 &#xB1; 4.4 years) randomly assigned to a control group (no additional exercise), continuous circuit training group (40 weeks continuous), and a circuit training followed by a detraining period group (training weeks 1-20, no training weeks 21-40). The circuit training groups performed a progressive small-group training routine of 10-12 exercises (strength, <a id="stability" data-tip="1191" target="_blank" href="/glossary-term/stability" class="glossary">stability</a>, and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercises for the whole body) performed 3x/week, 2-3 circuits/session, 20-40 sec/set, with 20-40 sec rest between exercises. The study demonstrated that circuit training resulted in increased energy expenditure during and following exercise, a decrease in body weight and body fat %, increased lean body mass, increased strength, increased VO2 max, and some improvements were retained following 20 weeks of detraining (49). Hermassi et al. compared 22 male handball players (in-season) (age 20.3 &#xB1; 0.5 years) randomly assigned to a control group (no additional resistance training), or a circuit training group (pull-over, bench press, half back squat, inclined chest press machine) for 8 weeks, 2x/week, 2-day split, rep tempo as fast as possible on both days; Day 1: 80 - 95% of 1-RM, 3-6 sets/exercise, 3 reps/set, 3-4 min rest intervals as needed; Day 2: 55 - 75% of 1-RM, 2- 4 sets/exercise, 3 -6 reps/set, 1 - 1.5 min rest intervals as needed. The findings demonstrated that the circuit training group exhibited a significant increase in lean body mass, decrease in body fat %, increase in leg and upper arm volume, and significant increases in strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> (50). Contrary to the research discussed above, these studies suggest that both overweight and athletic individuals may achieve significant changes in body fat % following just 8 weeks of circuit training. It is worth noting that these studies included circuit training protocols, or a combination of circuit training and sport, that resulted in high volumes of activity.
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 Author&apos;s Note: Statistically Significant Changes in Body Fat % are Challenging to Demonstrate
 It should be noted that studies investigating the correlation between exercise and changes in body fat % are inconsistent. This may be due to numerous factors including the <a id="accuracy" data-tip="1218" target="_blank" href="/glossary-term/accuracy" class="glossary">accuracy</a> of body fat measurement techniques (e.g. relatively large margin of error), the relatively small sample sizes used in most exercise science research, and the relatively small change in percentages that occur following long periods of training (e.g. 15% to 13% body fat). Note, a change of 2% body fat is a pride-worthy accomplishment that likely represents a loss of 3 - 5 lbs of fat and a caloric deficit of between 10,000 - 15,000 calories. Unfortunately, the difference between 15% and 13% body fat, with a sample size of 10 participants, may be mathematically insufficient to demonstrate statistically significant changes with an industry standard of &quot;p-value &#x2264; 0.05&quot;.
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<h4>What Type of Circuit Training is Best for Altering Body Composition?</h4>
Studies demonstrate that improvements in body composition from circuit training are unlikely to be <a id="specificity" data-tip="1224" target="_blank" href="/glossary-term/specificity" class="glossary">specific</a> to the type of circuit training. Sperlich et al. compared 19 overweight women (age: 23 &#xB1; 2 years) performing either a high-intensity functional exercise circuit, or a program that included high-volume, low-intensity exercise at 65% of max HR for 9 weeks, 3x/week. The findings demonstrated that both routines resulted in similar changes in lean body mass, body fat %, body mass index, and waist-to-hip ratio (51). Balachandran et al. compared 21 sarcopenic obese adults (age: 60 - 90 years) performing 15 weeks of conventional resistance training, or circuit training on 11 machines targeting major <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> groups. Conventional resistance training included 3 sets/exercise, 10-12 reps/set, 70% of 1-RM, moderate (1-2 min) rest between sets, and a moderate tempo (2:0:1), and circuit training included 3 sets/exercise, 10-12 reps/set, 70% of 1-RM, no rest between sets (1-2 min rest between circuits), and a moderate tempo (2:0:1). The findings demonstrated that body fat % improvement were similar for both groups (52). These studies suggest that functional exercises, conventional resistance training exercises, and circuit training with or without rest between exercises, likely result in similar improvements in body composition.
<h4>What Acute Variables Most Influence Body Composition?</h4>
Improving body composition following circuit training may be more dependent on acute variables than types of exercise. An RCT by Paoli et al. (2010) compared 40 participants (age: 50 - 65 years) randomly assigned to a control group (no exercise), an aerobic endurance training group, a low-load circuit training group, or a high-load circuit training group. The exercise groups trained for 12 weeks, 3x/week, for approximately 50 min/session. The aerobic exercise was performed on a treadmill at 65% of max HR. Both circuit training protocols included 3 circuits/session of a full body routine (underhand cable pull-downs, pectoral machine, <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> shoulder raises, horizontal leg press, and crunches); low-load circuit training included 15 reps/set and 60 sec rest between exercises; and the high-intensity circuit training used a rest-pause protocol of 6 RM, 20 sec rest, 2RM, 20 sec rest, 1-RM with 20 sec rest repeated to exhaustion. The findings demonstrated that larger improvements in weight, body fat %, waistline circumference, and 6RM strength were exhibited by the high-load circuit training group (53). Marx et al. compared 34 active but un-trained women (age: 23.2 &#xB1; 4.5 years) randomly assigned to a single-set circuit group, or a multi-set periodized program group. The single-set circuit group alternated between 2 different 10 exercise circuits (full body, single joint, and compound movements) for 24 weeks, 3x/week, 1 set/exercise, 8-12 RM/set, moderate (1-2 min) rest between sets, and a slow rep tempo (4:0:2). The multi-set periodized circuit group alternated between 2 different routines that included exercises similar to the single-set group, or exercises including Olympic and max strength lifts (e.g. squats, hang-cleans, bench press, push, press, etc.) for 24 weeks, 4x/week, 2-4 sets/exercise, 3-15 RM/set, moderate (1-2 min) rest between sets with lighter loads, long (3-4 min) rest between sets with heavier loads, slow rep tempo (4:0:2) with lighter loads, and a volitional tempo during explosive and heavy loads. The findings demonstrated that both groups exhibited similar improvements at 12 weeks. However, from 12-24 weeks the single-set group did not exhibit additional improvements, and the multi-set group exhibited additional increases in lean body mass, 3x the decrease in body fat%, increased <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> strength, and increased strength endurance (54). An RCT by Romero-Arenas et al. compared 37 healthy men and women (61.6 &#xB1; 5.3 years) randomly assigned to a control group (no additional activity), a conventional strength training group, or a high resistance circuit training group. The exercise groups trained for 12 weeks, 2x/week, with 1-3 sets/exercise. Conventional strength training included 2 groups of 3 exercises (leg curls, pec deck, seated calf raises) with 2 warm-up sets/exercise (12 reps at 50% of 6-RM, 10 reps at 75% of 6RM), followed by 1-3 sets/exercise with 6 RM loads, with long (3 min) rest between sets, and a moderate tempo (3 sec eccentric), followed by a 5 min rest, and then the second set of 3 exercises (seated pulley row, leg extension, and preacher curl) using the same protocol. The circuit training group used the same parameters but performed each block of 3 exercises in a circuit with 35 sec rest between exercises. The findings demonstrated that conventional strength training and circuit training resulted in similar improvements in strength; however, the circuit training group exhibited <a id="superior" data-tip="1570" target="_blank" href="/glossary-term/superior" class="glossary">superior</a> improvement in body composition (decrease in body fat and increase in lean mass) and cardiovascular performance (incremental treadmill <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>) (55). Another study by Paoli et al. (2021) compared 9 male and 9 female volunteers (age: 23.29 &#xB1; 1.89 years) randomly assigned to a &quot;spot reduction circuit&quot; group, or a resistance training circuit group, performed for 8 weeks, 3x/week. The routines included similar exercises, in different orders, with unequal total work (the spot reduction circuit included more total work). The findings demonstrated that only the &quot;spot reduction circuit&quot; resulted in a significant decrease in body weight and body fat%, resulting in an inability to determine whether any differences in site-specific fat reduction resulted from the spot reduction routine (56). In summary, larger decreases in body fat% may follow training with higher intensity (load), higher volume (total sets), and/or performed with a circuit protocol. It may be worth noting that the protocols resulting in the largest change, were often more detailed and progressed over time.

<h4>Circuit Training Compared to Aerobic Training for Body Composition:</h4>
Two studies discussed above compared body composition following aerobic training and circuit training. An RCT by Gettman et al. compared 41 adult men randomly assigned to a control group (no exercise), a circuit resistance training group, or a running group for&#xA0;20 weeks, 3x/week. When compared to controls, circuit training significantly improved strength and body fat %, and the running group significantly improved VO2max but did not improve body fat % (11).&#xA0;An RCT by Camargo et al. compared 20 healthy male subjects (age: 30 &#xB1; 4 years) randomly assigned to a control group (no additional activity), a circuit training group, or an aerobic training group for 12 weeks, 3x/week, 36 sessions total, 35 min/session. The findings demonstrated that aerobic training and circuit training resulted in similar reductions in body fat %; however, circuit training resulted in a significant increase in&#xA0;lean body mass (19). These studies suggest&#xA0;circuit training and aerobic training may be equally effective at reducing body fat %. However, these studies may also suggest that circuit training is more effective, in part due to the larger increases in lean body mass.
<h4>Combining Circuit Training and Aerobic Training for Improving Body Composition</h4>
Two studies mentioned above by Gettman et al. investigated body composition following a combination of aerobic and resistance training. First, an RCT by Gettman et al. (1982) compared 36 females (mean age = 35.7 yr) and 41 males (mean age = 36.1 yr) randomly assigned to a control group (no exercise), a circuit training group, or a circuit training with 30 sec of running between stations group, for 12 weeks, 3x/week. When compared to controls, the circuit training groups, with and without 30 sec of running, exhibited improvements in VO2 max, strength, and body fat %; however, differences between groups did not reach statistical significance (24). And, Gettman et al. (1979) compared 16 individuals (mean age: 29 yrs) performing 8 weeks of circuit training, followed by 8 weeks of aerobic training, followed by 8 weeks of aerobic or circuit training. The findings demonstrated that the initial 8 weeks of circuit training resulted in significant improvements in body fat %, lean body mass, and circumference measurements; however, an additional 8 weeks of circuit training did not result in significant additional improvements. The initial 8 weeks of aerobic training resulted in significant and similar changes in body fat %, lean body mass, and circumference measurements; however, the additional 8 weeks of aerobic training resulted in significant additional improvements (25). These studies imply that the addition of 30 seconds of running between stations of a circuit training routine is likely insufficient to result in additional improvements in body composition. However, following 8 weeks of circuit training or aerobic training, an additional 8 weeks of aerobic training was more likely to result in additional improvements in body composition when compared to circuit training.

Circuit Training Compared to Aerobic Training for Body Composition Change

Circuit Training added to Sport and Physical Occupations

Several studies have compared outcomes following the addition of circuit training to sports training. Two studies by Saini et al. and Bhardwaj et al. (may be duplicates of the same study) compared 60 and 120 male basketball players (age: 12 - 16 years) randomly assigned to a control group (no additional training), or a resistance training group. The resistance training group trained for 6 weeks, 6 days/week, with a 2-day split routine (<a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> and circuit), for 60 min/session. <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> training included 5 exercises (example: jump squats, box jumps, side jumps, strides, and skipping), 2-4 sets/exercise, 15 - 20 reps/set, performed on Monday, Wednesday, and Friday. Circuit training included 8 exercises (jumping jacks, kicking back, high knee strides, side hops, squats, flutter kicks, pilates leg pull x 2), 3 sets/exercise, 20 - 45 sec/set, performed on Tuesday, Thursday, and Saturday. The findings demonstrated that the training group exhibited significant improvements on the standing long jump and 10x10 shuttle run tests (57, 58). Two studies by Shekhawat et al. compared 30 male school-level basketball players (age: 15 - 18 years) based on a variety of <a id="assessment" data-tip="1480" target="_blank" href="/glossary-term/assessment" class="glossary">assessments</a>, before and after a circuit training program. The circuit training program included 10 exercises (jump rope, squat jumps with bodyweight, push-ups, jumping jacks, plank jacks, mountain climbers, bench dips, step-ups, back extensions, and <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> hops over line) performed for 10 weeks, 3x/week, 6-10 circuits/session, 30 sec/exercise, with 30 sec rest between exercises. The findings of both studies demonstrated significant improvements in performance, including pull-ups, bent-knee sit-ups, broad jumps, 50m sprint time, and 4x10m shuttle run time (59, 60). Strelnikowa et al. compared 32 basketball players (age: 18-19 years) randomly assigned to a control group (no additional activity) or a circuit training group. Circuit training included 4 blocks of strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercise. An example might include, block 1: barrier jumps single leg (low barriers) x 20/foot, high bar squat or low bar squat (10-20 times ), rope jumps (100-150 times), and vertical jumps with a touch of a basketball hoop (10 jumps); block 2: load 30-40% of bodyweight, close grip barbell for 5 sets of 5 reps, seated barbell military press for 5 sets of 5 reps, calf raise in a standing position for 2 sets of 20 reps, incline bench press for 5 sets of 5 reps, etc... This type of routine was performed for 7 months, 2x/week during pre-season, and 1x/week during in-season. The findings demonstrated that both groups exhibited improvements for the standing long jump, vertical jump, pull-ups, and leg raise assessments; however, the circuit training group exhibited significantly larger improvements (61). Freitas et al. compared 9 semi-professional basketball players (age: 21.44 &#xB1; 2.5 years) performing high-load, or low-load/high-velocity training protocols. Both protocols included a 2-block circuit (Block 1: 1/2 squats, bench press, ankle extensions; Block 2: lat pull-downs, knee flexions, elbow extensions), for 4 sets/exercise, 6 RM/set, 40 sec rest between exercises, and 5 min rest between blocks, the only difference in the routines was load and velocity. The findings demonstrated that immediately following the high-load protocol the participants exhibited a significant decrease in <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, agility, and shooting accuracy; however, immediately following the light-load/high-velocity protocol they did not exhibit a decrease in performance (62). These studies suggest that the addition of strength or <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> circuit training to a basketball program is effective for improving endurance, strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> in children, teenagers, and young adults. However, it may be recommended that <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> circuits, and not maximal strength circuits, are performed before basketball practices or games.
<img src="https://www.datocms-assets.com/25800/1661786046-basketball-compressed.jpg" width="452" height="339" title="Image of basketball players, which may benefit from the use of circuits in their training programs" alt="Basketball players ">

Two studies investigated the effects of adding circuit training to soccer training. Kumar et al. compared 40 male college football (soccer) players (age: 18-23 years) randomly assigned to a control group (no additional activity) or a circuit training group. Circuit training included 6 exercises (squat jumps, burpees, high knees, sit-ups, bicycle kicks, and single leg kick backs) performed for 6 weeks, 3x/week, for 3 circuits/session. The findings demonstrated no difference between groups for the 50 yard dash, or Southeast Missouri Agility <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">Test</a> (SEMO); however, only the circuit training group exhibited significant improvements on the 12 min run/walk <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">Test</a> (63). An RCT by Kundu, S. compared 45 male football (soccer) players (age: 18 - 22 years) randomly assigned to a control group (no additional training), a circuit training group, or a <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercise group. Both exercise programs were performed for 8 weeks, 3x/week. The circuit training included 60-70% of 1-RM loads during 10 exercises (push ups, half squats, push press, heel raises, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> cleans, leg curls, medicine ball push, sit ups, arm curls, and squat jumps); and the <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> routine included 9 body-weight exercises (drop jump, tuck jump, split jump, bounding, single leg hop, hurdling, medicine-ball exercises, stepping, and box jumps). The findings demonstrated that both groups exhibited significant improvements during leg extension dynamometry; however, the circuit training group exhibited significantly larger improvements (64). These studies suggest that the addition of circuit training is beneficial for football (soccer) players; however, they may improve more from endurance and strength exercise when compared to <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercises.

Handball athletes may also exhibit improvements in performance following the addition of circuit training. Selvam et al. compared 30 male handball players (age: 18-22 years) randomly assigned into a control group (no additional training) or a circuit training group. Circuit training (squat jumps, burpees, dumbbell squats. swings, tuck jumps, squat thrusts, fast feet on box, jumping jacks, and alternating split squats) was performed for 12 weeks, 3x/week, for 45 - 60 min/session. The findings demonstrated that the circuit training group exhibited a significant increase of lumbar extension strength (maximum voluntary isometric contraction) and <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> endurance (total reps during a bent knee sit-ups <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>) (65). Hermassi et al. compared 22 male handball players (in-season) (age 20.3 &#xB1; 0.5 years) randomly assigned to a control group (no additional resistance training) or a circuit training group. The circuit training (pull-overs, bench press, half back squats, inclined chest press machine) was performed for 8 weeks, 2x/week, rep tempo as fast as possible, with a 2-day split. The day 1 routine included 80 - 95% of 1-RM, 3-6 sets/exercise, 3 reps/set, and long (3-4 min) rest between sets as needed; and day 2 included 55 - 75% of 1-RM, 2-4 sets/exercise, 3-6 reps/set, and short (1-1.5 min) rest between sets as needed. The findings demonstrated that the circuit training group exhibited significant increases in lean body mass, decreases in body fat %, increases in leg and upper arm volume, significant increases in strength for all trained movements, improvements in 3-step throwing velocity, T-test speed, and counter-movement jump; however, no significant improvements were noted for squat jump performance (50). Hermassi et al. compared 19 elite male handball players (age: 18.5 &#xB1; 0.85 years) randomly assigned to a control group (standard in-season training) or a circuit training group (replacing a portion of in-season training). Circuit training (combination of calisthenics, strength, and bodyweight exercises) was performed for 12 weeks, 2x/week, 2 circuits/session, reps until failure/set, and 3 min rest between circuits. The findings demonstrated that replacing a portion of in-season training with 12 weeks of circuit resistance training resulted in <a id="superior" data-tip="1570" target="_blank" href="/glossary-term/superior" class="glossary">superior</a> increases in strength, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, sprinting, and change of direction performance (66). These studies suggest that handball athletes replacing some sports-specific training, or adding circuit training, may significantly improve <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> endurance, strength, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, agility, and potentially body composition and hypertrophy.
<img src="https://www.datocms-assets.com/25800/1661787143-handball-compressed.jpg" title="Image of athletes playing handball" alt="Players on a handball court">

Similar findings have been demonstrated when circuit training is added to volleyball and tennis training. Hartati et al. compared 30 female high school senior volleyball players (age: 17 &#xB1; 1 years), before and after 8 weeks of circuit training. The circuit training (push ups, seated dips, pull ups, bird dogs, straight arm planks on ball, straight arm plank &#x2013; single-leg hip extension with feet elevated, straight-arm plank - suspended upper body with single-leg hip extension, box walk up, and suspended lower body with walk out and back) was performed 4x/week, 3 sets/exercises, with 70% of 1 RM loads. The findings demonstrated that circuit training resulted in a significant increase in strength (67). An RCT by Mohanta et al. compared 40 male lawn tennis players (age: 18 - 25 years) following 8 weeks of either circuit training or <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> training. The circuit training group performed a progressive routine of strength, agility, and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercises (seated rows, chest press, <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> raise, sit-up-toss, planks, crunches, footwork patterns, and depth jumps), for 2-3 circuits/session, 30 - 60 sec/set, and 60 sec rest between exercises. The <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> training group performed a variety of <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> exercises with a progressive increase in intensity and volume (example program: 2-foot ankle hop forward, 2-leg box hopping, counter movement jumps, chest throws, overhead throws, close stance throws) for 2 - 4 sets/exercise, 10 - 15 reps/set, and moderate (90 sec) rest between sets. The findings demonstrated that both groups exhibited significant improvements; however, the circuit training group exhibited larger improvements in strength, agility, and running speed (68). In summary, the addition of circuit training may result in significant increases in endurance, strength, and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, and may be more beneficial than <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> training for volleyball and tennis athletes.

Mixed sports athletes may also benefit from the addition of circuit resistance training. An RCT by Rawat et al. compared 90 college athletes (age: 18 - 24 years) randomly assigned to a control group (no additional activity), a circuit training group, or a conventional <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training group for 8 weeks, 3x/ week. The circuit training included 8 bodyweight exercises (jumping jacks, burpees, crunches, high knees, half squats, triceps dips, butt kicks, and push-ups), and conventional <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training included a mix of bodyweight strength and <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> exercises (squat jumps, bodyweight squats, box jumps, box single-leg <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> crossover steps, explosive push-ups, box inverted shoulder press, rope inverted lat row, and box dips). The findings demonstrated that compared to controls, both training groups improved similarly during re-assessment of 50-meter dash speeds (69). Taskin et al. compared 32 healthy male physical education students (age: 23.92 &#xB1; 1.51 years) randomly assigned to a control group (no additional training) or a circuit training group. Circuit training included 8 stations (jump rope, sit-ups, hurdle hops, push-ups, jack knifes, jump squats, supermans, and commando dance) performed for 10 weeks, 3x/week, 3 circuits/session, 75% of max reps/station, 40-60 sec rest between stations, and no additional load used for any exercise. The findings demonstrated that the circuit training group exhibited significantly larger improvements on a speed/agility <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a> (4 line sprint <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>), and HR recovery <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a> (3-corner run <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>) (70). These studies demonstrate that even when athletes are involved in a mix of sports they may attain significant improvements in speed, agility, and heart rate recovery with the addition of a circuit training routine.

Fire-fighting, military, and law enforcement officers may attain a variety of positive physical and mental health benefits from the addition of circuit training. Hofstetter et al. compared 259 fusilier infantry training school recruits (age: 20.4 &#xB1; 1.2 years) randomly assigned to a control group (standard training), standard training group, or a circuit training group. Circuit training (warm-up, squats, <a id="prone" data-tip="1561" target="_blank" href="/glossary-term/prone" class="glossary">prone</a> bridges, back and shoulder exercises, stair climbing, side bridges, single leg <a id="balance" data-tip="1190" target="_blank" href="/glossary-term/balance" class="glossary">balance</a>, walking on a <a id="balance" data-tip="1190" target="_blank" href="/glossary-term/balance" class="glossary">balance</a> beam, intermitted running, and active recovery) was performed for 8 weeks, 1x/week, for 60 minutes, outdoors, in addition to standard training. The circuit training group exhibited larger improvements during re-assessment of trunk <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> endurance, one-legged standing <a id="balance" data-tip="1190" target="_blank" href="/glossary-term/balance" class="glossary">balance</a>, and a physical fitness battery, and without an increase in the frequency of injury (71). Getty et al. compared 25 non-firefighting age-matched controls (age: 36.2&#x202F;&#xB1;&#x202F;13.7 years) to 27 volunteer firefighters (age: 34.4&#x202F;&#xB1;&#x202F;15.2 years) performing circuit training. Circuit training included 6 stations (40&#x202F;lb. carry for 100&#x202F;ft, 3 min stair climb, 45&#x202F;s plank pose, 20&#x202F;lb carry with a fast walk for 100&#x202F;ft, right and left single leg stance for as long as <a id="balance" data-tip="1190" target="_blank" href="/glossary-term/balance" class="glossary">balance</a> was maintained, and a 15&#x202F;lb. carry up and down 30 stairs) for 4 weeks, 3x/week, 3 circuits/session. The findings demonstrated that both groups showed significant improvements in carotid artery intima-media thickness, brachial artery flow-mediated dilation, pulse pressure, and brachial and central blood pressure (72). As mentioned above, Norvell et al. compared 43 male state law enforcement officers (age: 20-47 years) who were not regularly exercising when enrolled in the study. Participants were randomly assigned to a waitlist control group or circuit training group for 16 weeks, 3x/week. The findings demonstrated that the circuit training group exhibited a significant increase in strength and cardiovascular performance; as well as improvements in mood, somatization, anxiety, depression, hostility, reports of physical symptoms, and job satisfaction (46). These studies suggest that firefighters, law enforcement officers, and military recruits, following 4 - 16 weeks of circuit training, may improve <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> endurance, strength, <a id="balance" data-tip="1190" target="_blank" href="/glossary-term/balance" class="glossary">balance</a>, conditioning, cardiovascular health measures, mental health, and job satisfaction; without an increase in the risk of injury.

Occupation (Fire-fighting, Law Enforcement, and the Military)

<h4>Circuit Training is Effective</h4>
Studies have demonstrated that young children also benefit from the addition of circuit training. An RCT by Maniazhagu et al. compared 30 girls (age: 11-13 years) randomly assigned to a control group (no additional activity), a strength circuit group, and a battle rope circuit group. The strength training circuit (vertical jumps, push ups, high knee actions, dumbbells bicep curls, back kicks, upper body medicine ball, burpees, bent-knee sit-ups) progressed in volume for 6 weeks, 5 days/week, 3 circuits/session, 15-25 sec/set, 15-25 sec rest between sets, 5 min rest between circuits. The battle rope circuit (double waves, alternate waves, lower alternate waves, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> slams, alternating wave lunge jumps) progressed in volume for 6 weeks, 5 days/week, 2 circuits/session, 10-30 sec/set, 2 - 4 sets/exercise, 1 min rest between sets, 5 min rest between circuits. The findings demonstrated that both training groups exhibited similar and significant improvements during reassessment of 40m sprint times (73). An RCT by Hendrawan et al. compared 30 children (age: 11-12 years) divided into a control group (no additional activity), a game circuit group, and a ladder circuit group. The program was performed for 6 weeks, 3x/week; however, no further details were given regarding these programs. The findings suggest that both the game circuit group and ladder circuit training group exhibited improvements for 30 m sprint and agility <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a> times when compared to controls; however, the agility circuit group improved significantly more (74). These studies demonstrate that circuit training is an effective intervention for improving speed and agility in young children; however, more research is needed to determine the influence of exercise selection on outcomes.
<h4>Circuit Training Added to Activity</h4>
Additional studies have investigated the benefits of adding circuit training to organized youth sports and gym classes. An RCT by Boraczy&#x144;ski et al. compared 67 boys (age: 11.2 &#xB1; 0.7 years) randomly assigned to a control group (no training regimen), a soccer training and moderate intensity circuit (higher volume) group, and a soccer training and high intensity circuit group. Circuit training included 9 upper-body and lower-body exercises (sample program: high knees, box jumps, butt kicks, Russian twists, burpees, jump taps, walking lunges, mountain climbers, and 40m repeated sprints) and was performed for 6 months, 3x/week. The moderate intensity group performed 2-3 sets/exercise, 60 sec/set, HR 150-170 bpm, with 30 sec rest between exercises (2:1 work/rest ratio), and the high intensity group performed 2 -3 sets/exercise, 30 sec/set, HR 170&#x2013;190 bpm, with 30 sec rest between exercises (1:1 work/rest ratio). The findings demonstrated that the high intensity (lower volume) group exhibited larger improvements than the moderate intensity (higher volume) group on the <a id="assessment" data-tip="1480" target="_blank" href="/glossary-term/assessment" class="glossary">assessments</a> included in the Eurofit <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a> (flamingo <a id="balance" data-tip="1190" target="_blank" href="/glossary-term/balance" class="glossary">balance</a>, plate tapping, sit-and-reach, standing broad jump, handgrip, sit-ups, bent arm hang, 10&#xD7;5 m shuttle run, and the Physical Working Capacity <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>). The largest differences were noted for the standing broad jump, flamingo <a id="balance" data-tip="1190" target="_blank" href="/glossary-term/balance" class="glossary">balance</a>, and sit and reach tests (75). Faigenbaum et al. compared 41 elementary school children (age: 9.5 &#xB1; 0.3 years) divided into a control group (normal physical education class activity) or a circuit training group. The circuit training group included 6-7 exercise stations that focused on enhancing muscular &#xFB01;tness and fundamental movement skills, and was performed for 8 weeks, 15 min/session, 30 sec/exercise for weeks 1-4, 45 sec/exercise for weeks 5 - 8, and 30 sec rest between exercises. The findings demonstrated that the circuit group exhibited significantly larger improvements on the progressive aerobic cardiovascular endurance run (PACER), push-ups, single-leg hops, and sit and reach tests, but no significant differences were noted for the sit-ups for reps or long jump tests (76). Last, Mayorga-Vega et al. compared 72 school children, (40 boys, 32 girls; age 11.10 &#xB1; 0.38 years) randomly assigned to a control group (organized sports) or a circuit training group. The circuit training included 8 stations (chest pass, rowing, up-downs, triceps extensions, bicep curls, skipping rope, crunches, and bridges) performed for 2 circuits/session, with a progressive increase in activity from 15-35 sec/set, and 25 - 45 sec rest between sets. Both groups performed activity 2x/week for 8 weeks, followed by 4 weeks of detraining, followed by an additional 4 weeks of &quot;maintenance&quot;. Maintenance included 2 sports days for the control group, a circuit day, and a sport day for the circuit training group. The circuit training group demonstrated significantly larger improvements during re-assessment of the sit-ups in 30 seconds <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>, bent arm hang <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>, and 20 meter endurance shuttle run <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a> (77, 78). In summary, the addition of circuit training to organized sports or gym classes may improve the endurance, strength, speed, agility, and fitness battery tests of young children. Further, larger improvements may be attained from higher intensity activity, and some of these improvements may be retained following a period of detraining and/or maintenance.

Hypertrophy

Several studies have demonstrated that circuit training can result in <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> hypertrophy and an increase in lean body weight. As mentioned above, Wilmore et al. compared 49 men and women randomly assigned to a control group (no additional activity), or a circuit training group, for 10 weeks, 3x/week. The findings demonstrated significant improvements in lean body weight, skinfold measurements, and flexed bicep circumference (7). Marcos-Pardo et al. compared 45 participants (27 females, 18 males, age 65 - 75 years) randomly assigned to a control group (no exercise) or a progressive circuit training group. The progressive circuit training program was performed for 12 weeks, 3 sessions/week, 3 sets/exercise, 8-12 RM/set, with 60 - 80% of 1-RM loads, and a moderate (1-2 min) rest between sets. The findings demonstrated that participants exhibited an increase in lean body mass, strength, and functional capacity (79). Also mentioned above, Harber et al. compared 12 men (age: 18 - 35 years) randomly assigned to a control group (no exercise), or a timed circuit training program. The circuit training program included exercises performed on 10 Nautilus and Hammer Strength machines for 10 weeks, 3x/week. The findings demonstrated that circuit training resulted in a trend toward improvements in circumference, body fat %, and fat-free mass, but the effect size did not reach statistical significance. <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> biopsy demonstrated an increase in type IIa fiber cross-sectional area, an increase in the percentage of IIa myosin proteins, and a decrease in the % of type IIb myosin proteins (34). Another RCT mentioned above by Batrakoulis et al. compared 49 healthy overweight females (age: 36.4 &#xB1; 4.4 years) randomly assigned to a control group (no additional exercise), a continuous circuit training group (40 weeks continuous), or a circuit training followed by detraining group (training weeks 1-20, no training weeks 21-40). The study demonstrated that circuit training resulted in a decrease in body weight and body fat %, increased lean body mass, increased strength, and some but not all improvements diminished following 5 months of detraining (49). These studies demonstrate that when compared to controls (no additional activity), circuit training is an effective method for increasing lean body mass and <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> hypertrophy, even when training is followed by a significant period of de-training. Specifically, circuit resistance training has a significant effect on the proportion and size of type IIa <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> fibers.

Several studies have demonstrated that circuit training results in similar changes in lean body mass and hypertrophy as other forms of resistance training. An RCT by Alcaraz et al. compared 38 resistance trained men (age: 22.7 6 3.3 years) randomly assigned to a control group (no additional activity), a conventional strength training group, or a circuit training group. The exercise protocols included 6 exercises (Block 1: pec deck, knee extensions, elbow flexion, and block 2: knee flexions, lat pull-downs, and ankle extensions) for 8 weeks, 3x week, 3-6 sets/exercise, 6-RM loads (~85&#x2013;90% of 1-RM), and a moderate tempo (3:0:1). The conventional resistance training protocol included 3-min rest between sets and 5-min rest between blocks, and the circuit training protocol included 35 sec rest between exercises and 5 min rest between blocks. The findings demonstrated that improvements in lean body mass, 1-RM strength, peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, and shuttle run performance were similar for both groups (80). As mentioned above, Balachandran et al. compared 21 sarcopenic obese adults (age: 60 - 90 years) randomly assigned to a conventional resistance training group, or a circuit training group, for 15 weeks. The findings demonstrated that both groups exhibited similar improvements on the Skeletal <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">Muscle</a> Index (SMI) and similar reductions in body fat % (52). Also mentioned above, Sperlich et al. compared 19 overweight women (age: 23 &#xB1; 2 years) performing either a high-intensity functional exercise circuit or a program that included high-volume, low-intensity exercise at 65% of max HR, for 9 weeks, 3x/week. The findings demonstrated that both routines resulted in similar changes in lean body mass, body fat %, body mass index, and waist-to-hip ratio (51). These studies suggest that circuit training, conventional resistance training, and high-intensity functional exercise training, result in similar changes in performance, body fat %, and lean body mass.

Two studies mentioned above compared changes in lean body mass following aerobic training and circuit resistance training. An RCT by Camargo et al. compared 20 healthy male subjects (age: 30 &#xB1; 4 years) randomly assigned to a control group (no additional activity), a circuit training group, or an aerobic training group for 12 weeks, 3x/week, 36 sessions total, 35 min/session. The findings demonstrated similar decreases in body fat % and increases in lower body strength; however, circuit training exhibited <a id="superior" data-tip="1570" target="_blank" href="/glossary-term/superior" class="glossary">superior</a> improvements for upper body strength and increased lean body mass (19). Gettman et al. compared 16 individuals (mean age: 29 yrs) performing 8 weeks of circuit training, followed by 8 weeks of aerobic training, followed by 8 weeks of aerobic or circuit training. The findings demonstrated that an additional 8 weeks of circuit training resulted in significant improvements in body fat %, lean body mass, and circumference measurements. An additional 8 weeks of aerobic training actually resulted in larger reductions in body fat % and waist circumference but did not increase lean body mass (25). These studies suggest that circuit training results in larger improvements in lean body mass, hypertrophy, and <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> strength when compared to aerobic training.

A group of 4 publications by the same group (discussed below), compared heavy circuit training with normal (normoxic) and decreased (hypoxic) oxygen environments; two of these publications included lean body mass and/or hypertrophy as outcome measures. Ramos-Campo et al. compared 28 resistance-trained male subjects (age: 24.6 &#xB1; 6.8 years) during&#xA0;normoxic and hypoxic conditions while performing high load circuit training. The circuit training protocol (Circuit 1: bench press, leg extensions, and front lat pulldown; Circuit 2: deadlifts, elbow flexions, and ankle extensions) was performed for 8 weeks, 2x/week, 2 circuits/session, 3 sets/exercise, 6 reps/set, 6-RM loads, 35 sec rest between exercises, 3 min rest between cycles, and 5 minutes rest between circuits. The findings demonstrated that both groups exhibited similar improvements in <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> thickness, pennation angle (quadriceps), maximum voluntary isometric contraction, rate of force development, peak force development, and max HR (81). Conversely, a publication by&#xA0;Mart&#xED;nez-Guardado et al. (2019) with the same methodology, reported that lean body mass and bone mineral density increased significantly for the hypoxic group, but statistical significance was not reached by the normoxic group (82). These studies likely imply that&#xA0;hypoxic and normoxic environments likely result in similar improvements in strength and hypertrophy. However, some evidence suggests that training in hypoxic environments may augment benefits, which may have implications for resistance training at higher altitudes.

Two studies suggest that increasing exercise volume during circuit training may increase hypertrophy. As mentioned above, Hermassi et al. compared 22 male handball players (in-season) (age 20.3 &#xB1; 0.5 years) randomly assigned to a control group (continued sport training), or a circuit training group (pull-over, bench press, half back squat, inclined chest press machine) for 8 weeks, 2x/week. The findings demonstrated that the circuit training group exhibited a significant increase in lean body mass, decrease in body fat %, increase in leg and upper arm volume, and significant increases in strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> (50). Marx et al. compared 34 active, but un-trained, women (age: 23.2 &#xB1; 4.5 years) randomly assigned to a single-set circuit, or a multi-set periodized program, for 24 weeks. The single-set circuit group alternated between 2 different 10 exercise circuits (full body, single joint, and compound movements) 3x/week, 1 set/exercise, 8-12 RM/set, moderate (1-2 min) rest between sets, and a slow rep tempo (4:0:2). The multi-set periodized circuit group alternated between 2 different routines that included either similar exercises, or exercises including Olympic and max strength lifts (e.g. squats, hang-cleans, bench press, push, press, etc.), 4x/week, 2-4 sets/exercise, 3-15 RM/set, moderate (1-2 min) rest between sets for lighter loads, long (3-4 min) rest between sets for heavier loads, slow rep tempo (4:0:2) during lighter loads, and volitional tempo during explosive and heavy loads. The findings demonstrated that both groups exhibited similar improvements during re-assessment at 12 weeks. During re-assessment at 24 weeks the single-set group did not exhibit any additional improvements; however, the multi-set group exhibited significant additional improvements including an increase in lean body mass, 3 times the decrease in body fat %, increased strength and endurance, and improvements in levels of resting serum concentrations of testosterone, IGF-1, and cortisol (54). These studies suggest that the addition of circuit training to sport is likely to increase lean body mass and hypertrophy, and although a single set of circuit training may be sufficient to increase lean body mass for up to 12 weeks, additional sets should be added to attain additional improvements beyond 12 weeks.

Load and Volume

A few studies have compared circuit training with higher loads and lower volumes to circuit training with lower loads and higher volumes. As mentioned above, an RCT by Boraczy&#x144;ski et al. compared 67 boys (age: 11.2 &#xB1; 0.7 years) randomly assigned to a control group (no training regimen), a soccer training and moderate intensity circuit (higher volume) group, and a soccer training and high intensity circuit group, following 6 months, 3x/week. The moderate intensity group performed 2-3 sets/exercise, 60 sec/set, HR 150-170 bpm, with 30 sec rest between exercises (2:1 work/rest ratio), and the high intensity group performed 2 -3 sets/exercise, 30 sec/set, HR 170&#x2013;190 bpm, with 30 sec rest between exercises (1:1 work/rest ratio). The findings demonstrated that the high intensity (lower volume) group exhibited larger improvements than the moderate intensity (higher volume) group on the <a id="assessment" data-tip="1480" target="_blank" href="/glossary-term/assessment" class="glossary">assessments</a> included in the Eurofit <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>. Another RCT mentioned above by Paoli et al. (2010) compared 40 participants (age: 50 - 65 years) randomly assigned to a control group (no exercise), an aerobic endurance training group, a low-load circuit training group, or a high-load circuit training group. The exercise groups trained for 12 weeks, 3x/week, for approximately 50 min/session. Low-load circuit training included 15 reps/set and 60 sec rest between exercises; and the high-intensity circuit training used a rest-pause protocol of 6 RM, 20 sec rest, 2RM, 20 sec rest, 1-RM with 20 sec rest repeated to exhaustion. The findings demonstrated that larger improvements in weight, body fat %, waistline circumference, and 6RM strength were exhibited by the high-load circuit training group (53). A similar RCT by Paoli et al. (2013) compared 58 participants (ages: 61 &#xB1; 3.3 years) using the same methodology as the previous study, but without a control group. The findings demonstrated that both groups exhibited a significant and similar decrease in body weight, the higher load (lower volume) circuit training group exhibited the largest improvements in fat mass, diastolic blood pressure, total cholesterol, LDL-C (low-density lipoprotein-cholesterol), HDL-C (high-density lipoprotein-cholesterol), triglycerides, and ApoB, and the lower load, (higher volume) circuit training group exhibited the largest improvements in systolic blood pressure (83). These studies suggest that load has a larger influence than volume on improving strength, endurance, body composition, and various serum concentrations associated with general health. However, lower load (higher volume) routines may be more beneficial for improving systolic blood pressure.
<img title="Systole vs Diastole Blood Pressure" src="https://www.datocms-assets.com/25800/1653665380-systolevs_diastole.png" alt="Blood pressure (systolic and diastolic) ">

Additional studies imply a few exceptions to load being more influential than volume. An RCT by Hortobagyi et al. compared 28 college males randomly assigned to a control group (no additional activity), a low-resistance group, and high-resistance group. Training was performed for 13 weeks, 3x/week, and included a hydraulic resistive circuit of 7 upper and lower body exercises, and 6 supplementary exercises, 2 circuits/session, 20 sec/set, 40 sec rest between exercises, followed by running for 2 miles, and each session lasted about 40 min. The low resistance was set at a tempo of 100 cm/sec, and the high resistance was set at 50 cm/sec. The findings demonstrated that both groups exhibited similar improvements in <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> strength, <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> endurance, and run performance, and no change in body fat or circumference measurements (48). As mentioned above, Marx et al. compared 34 active, but un-trained, women (age: 23.2 &#xB1; 4.5 years) randomly assigned to a single-set circuit, or a multi-set periodized program, for 24 weeks. The single-set circuit group alternated between 2 different 10 exercise circuits (full body, single joint and compound movements) 3x/week, 1 set/exercise, 8-12 RM/set, moderate (1-2 min) rest between sets, and a slow rep tempo (4:0:2). The multi-set periodized circuit group alternated between 2 different routines that included either similar exercises, or exercises including Olympic and max strength lifts (e.g. squats, hang-cleans, bench press, push, press, etc.), 4x/week, 2-4 sets/exercise, 3-15 RM/set, moderate (1-2 min) rest between sets for lighter loads, long (3-4 min) rest between sets for heavier loads, slow rep tempo (4:0:2) during lighter loads, and volitional tempo during explosive and heavy loads. The findings demonstrated that both groups exhibited similar improvements during re-assessment at 12 weeks. During re-assessment at 24 weeks the single-set group did not exhibit any additional improvements; however, the multi-set group exhibited significant additional improvements including an increase in lean body mass, 3 times the decrease in body fat %, increased strength and endurance, and improvements in levels of resting serum concentrations of testosterone, IGF-1, and cortisol (54). Last, an RCT by Ahmed et al. compared 30 male judokas (age: 18-24 years) randomly assigned to a control group (no additional exercise), a lower load (higher volume) circuit training group, or a higher load (lower volume) circuit training group. Both circuit training groups performed the same exercises (horizontal press, half squats, biceps curls, leg press, triceps extensions, step ups, military press, sit-ups) for 6 weeks, 3x/week. The lighter load/higher volume circuit included 4 circuits/session, 30-40 sec/set, 30-40% 1-RM, 40 sec rest between exercises, 3 min rest between circuits, and speed of movement equal to competition. The higher load (lower volume) circuit included 3 circuits/session, 20-40 sec/60 sec sets, 50-65% 1-RM, 60 sec rest between exercises, 4 min rest between circuits, and speed of movement equal to competition. The findings demonstrated that both circuits were effective for improving strength, endurance, and speed of movement; however, the lower load group exhibited significantly larger improvements in speed of movement (84). These studies imply that untrained individuals may achieve similar benefits from training with low loads, high loads, low volume, or high volume for up to 12 weeks; however, beyond 12 weeks, load and volume should increase to achieve additional benefits. Further, athletes with the goal of increasing speed are likely to achieve larger improvements following maximal tempos with lighter loads, when compared to heavier load training.

The concept of frequent micro sessions is worthy of study due to the potential to improve exercise adoption; unfortunately, outcomes may not be positive enough to recommend to the general public. Sperlich et al. compared 24 inactive men and women (age: 18 - 40 years) randomly assigned to either 1x/day, or 2x/day, of 6 min circuit training sessions (push-ups, leg-levers, burpees, 45&#xB0; one-legged squats, and 30 sec skipping), performed every day for 4 weeks, with an intensity of 70-75% of max HR. The findings demonstrated that the maximal number of reps/exercise increased significantly, but similarly for both groups. HR during a 6km running <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a> decreased, however, max HR, submaximal oxygen uptake, respiratory exchange ratio, and peak oxygen uptake did not change. Additionally, subjective reports of general health improved despite a lack of significant change in body composition (85). Engel et al. compared 35 students (22 male, 13 female; age: 11.6 &#xB1; 0.2 years) randomly assigned to a control group (no additional activity) and a micro-session circuit training group. The micro-session circuit training included 6 min of exercise (exercise included: squats, lunges, burpees, skipping, jumping jacks, push-ups) for 4 weeks, 4x/week, 30-50 sec/set, 10-15 sec rest between sets, with an &quot;all out&quot; intensity of 17 on 6-20 Borg scale. The findings demonstrated no difference between circuit training and control groups on the German Motor Ability <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a> (20m sprint, standing long jump, forward bend, <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> jumping, balancing backward, sit-ups, push-ups, and 6 min run) (86). Schmidt et al. compared 96 recreationally active college-aged subjects (53 female, 43 male) randomly assigned to a control group (no training), a 7-min circuit training group, and a 14-min circuit training group. Circuit training included bodyweight exercise performed for 8 weeks, 3x/week. The 14 minute circuit group performed the same routine as the 7 minute circuit group for weeks 1-4, and performed the circuit 2x/session for weeks 5 - 8. The circuit training groups exhibited significant improvements during a push-up endurance <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a> (total reps), and females in the 14 min group exhibited significant improvements in aerobic performance (87). Armas et al. compared 6 males and 6 females (age: 20 - 35 years) performing 7 min of circuit training or 7 min of high-intensity interval training (HIIT) on a cycle ergometer. The circuit training consisted of 12 exercises (jumping jacks, wall sits, push-ups, abdominal crunches, 16&quot; step-ups, squats, triceps dips on step, planks (high or low), high knees, lunges, push-ups with rotation, and side planks), for 1 circuit/session (7 minutes), 30 sec/exercise, 5 sec rest between exercises, and tempo/rep dictated by a metronome. The HIIT group performed a similar pattern on a cycle ergometer, including 12 sets, 30 sec/set, 5 sec rest between sets, 70 RPM, and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> output adjusted to achieve 70 - 80% of max HR. The findings demonstrated that both protocols resulted in similar decreases in post-exercise serum blood glucose and blood triglycerides; however, circuit training resulted in a larger post-exercise decrease in diastolic blood pressure (18). These studies suggest that some benefits may be attained from daily 6 - 7 min circuit training sessions, including subjective reports of improved health, an increase in reps/set for the exercises performed in the circuit, some benefits for post-exercise concentrations of glucose and blood triglycerides, and 14-minutes may be enough for some initial improvements in aerobic performance. However, it would appear that the volume of exercise is insufficient to improve most measures of strength, cardiovascular performance, and body composition.

Comparing Routines

<h3>Functional Training versus Conventional Training</h3>
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 Defining &quot;Functional Training&quot;:
 Note, it is the author&apos;s opinion that the term &quot;functional training&quot; has been abused by the fitness industry, and in the fitness industry, the term no longer relates to improving daily function. &quot;Functional training&quot; likely originated in physical rehabilitation settings, where the term is conventionally defined as activities/exercises specifically designed to improve a patient&apos;s ability to perform an inhibited daily task. This might include putting a cup back in a tall cupboard, transferring from the toilet to standing, or performing a repetitive occupational activity without pain (e.g. moving boxes, hanging drywall, etc.). Considering this conventional definition, battle ropes, kettlebell swings, Olympic lifting, etc. cannot be defined as &quot;functional training&quot;. That is not a judgment on the quality of these exercises, but rather their relative effectiveness for improving activities of daily living when compared to more <a id="specificity" data-tip="1224" target="_blank" href="/glossary-term/specificity" class="glossary">specific</a> exercise selections. However, in the research below, &quot;functional training&quot; implies the current fitness industry use, which appears to be any approach that does not use machines, and is often performed with unconventional parameters or acute variables.
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Three studies were located that compared a &quot;functional training&quot; circuit to a conventional training protocol. As mentioned above, An RCT by Maniazhagu et al. compared 30 girls (age: 11-13 years) randomly assigned to a control group (no additional activity), a strength circuit group, and a battle rope circuit group, progressed in volume for 6 weeks, 5 days/week, 3 circuits/session. The findings demonstrated that both training groups exhibited similar and significant improvements during reassessment of 40m sprint times (73). Aragao-Santos et al. compared 44 elderly women (age: 65.4 &#xB1; 5.4 years) randomly assigned to a control group (no additional activity), a functional training group, or a traditional training group. Both training protocols were performed for 12 weeks, 3x/week, 8-12 reps/set, reps until failure/set, with 2 sets/exercise. The functional training group performed 15 minutes of intermittent agility, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, coordination, and cardiorespiratory fitness exercises, followed by a circuit of exercises targeting primarily <a id="stability" data-tip="1191" target="_blank" href="/glossary-term/stability" class="glossary">stability</a> muscles. The traditional training group performed 15 minutes of continuous aerobic activity followed by a circuit of mostly machines. The findings demonstrated that both groups exhibited significant improvements in strength, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, and endurance when compared to controls; however, the functional training group exhibited larger improvements during re-assessment of deadlift strength, and the traditional training group exhibited larger improvements during re-assessment of grip strength (88). Last, Sperlich et al. compared 19 overweight women (age: 23 &#xB1; 2 years) performing either a high-intensity functional exercise circuit, or a combined program that included high-volume low-intensity exercise at 65% of max HR, for 9 weeks, 3x/week. The findings demonstrated that both routines resulted in similar changes in lean body mass, body fat %, body mass index, waist-to-hip ratio, and RPE during a treadmill <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>, as well as performance improvements for push-ups, burpees, one-legged squats, 30s skipping, and counter-movement jump height. Additionally, similar improvements were noted for psychosocial factors including physical and social functioning, the role of physical limitations, vitality, and the role of emotional limitations, and mental health. The only difference in outcomes between the two groups was a reduction in the perception of physical pain, and an increase in feelings of general physical health for the group adding a day of high-volume/low intensity exercise (51). These studies demonstrate that functional training (as the term is currently being used in the fitness industry) and conventional training are likely to result in similar improvements in endurance, strength, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, cardiovascular performance, body composition, and mental health. However, some <a id="specificity" data-tip="1223" target="_blank" href="/glossary-term/specificity" class="glossary">specificity</a> can be expected, including free weight (functional) routines having a larger effect on strength <a id="assessment" data-tip="1478" target="_blank" href="/glossary-term/assessment" class="glossary">assessment</a> using free weight exercises, larger loads lifted (with machines) resulting in larger increases in grip strength, and the addition of low-intensity (high volume) exercise improving feelings of general physical well-being.
<img src="https://www.datocms-assets.com/25800/1661924753-bosu-compressed.jpg" width="510" height="339" title="Functional training on the BOSU ball, a common &quot;functional training&quot; tool used in the fitness industry" alt="An example of &quot;functional training&quot; used in many fitness and wellness facilities">

<h4>Teenagers and Young Adults</h4>
Teenagers and young adults may achieve additional benefits from the addition of &quot;stability exercise&quot; to circuit training routines. An RCT by Mat&#xE9;-Mu&#xF1;oz et al. compared 36 healthy untrained men (age: 22.3 &#xB1; 2.4 years) randomly assigned to a control group (no exercise), an <a id="stability" data-tip="1194" target="_blank" href="/glossary-term/stability" class="glossary">unstable</a> circuit with Bosu&#xAE; and TRX&#xAE;&#xA0; group, or a conventional exercise circuit group. Both circuits were performed for 7 weeks, 3x/week, 3 circuits/session, 15 reps/set, 1-2 min rest between sets, with a rep tempo of &quot;fastest comfortable speed&quot;. The <a id="stability" data-tip="1194" target="_blank" href="/glossary-term/stability" class="glossary">unstable</a> circuit with Bosu and TRX included TRX pulldowns, BOSU lunges, TRX incline push-ups, BOSU step-downs, TRX front raise inclines, TRX snatches, TRX dumbbell bicep curls, and TRX triceps-swinging body. The conventional exercise circuit included back pull-downs, dumbbell lunges, incline dumbbell bench presses, dumbbell step-downs, dumbbell shoulder presses, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> snatches, bicep curls, and triceps press downs. The findings demonstrated that both groups exhibited significant and similar improvements for strength, peak and average <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> during 1-RM testing of bench press and back squats, as well as significant improvements in squat jump and counter-movement jump performance (89). An RCT by Setyawan et al. compared 60 male students (average age 19 years) randomly assigned to a control group (no additional activity), a swiss ball exercise circuit group, or a floor exercise circuit group. Both exercise groups trained for 8 weeks, 3x/week, 2-3 circuits/session, 30 sec rest between exercises, and 2 min rest between circuits. The swiss ball exercise circuit included wall squats, bridges on a <a id="stability" data-tip="1191" target="_blank" href="/glossary-term/stability" class="glossary">stability</a> ball, single-leg bridges on a <a id="stability" data-tip="1191" target="_blank" href="/glossary-term/stability" class="glossary">stability</a> ball, single-leg hip lifts on a <a id="stability" data-tip="1191" target="_blank" href="/glossary-term/stability" class="glossary">stability</a> ball, single-leg glute bridges off the box, bird dog static <a id="balance" data-tip="1190" target="_blank" href="/glossary-term/balance" class="glossary">balance</a> on ball, <a id="stability" data-tip="1191" target="_blank" href="/glossary-term/stability" class="glossary">stability</a> ball leg rotations, gymball crunches with legs elevated, <a id="unilateral" data-tip="1551" target="_blank" href="/glossary-term/unilateral" class="glossary">unilateral</a> bridge on a <a id="stability" data-tip="1191" target="_blank" href="/glossary-term/stability" class="glossary">stability</a> ball, and reverse pendulum medicine ball twisters. And, the floor exercise circuit included wall sits, bridges on floor, single-leg bridging, pelvic tilts, single-leg glute bridges off the box, bird dogs, windshield wipers, crunches with legs elevated, and lying hip stretch reverse pendulums. The findings demonstrated that both exercise groups exhibited significant and similar flexibility, endurance, and limb strength improvements; however, the swiss ball exercise group demonstrated <a id="superior" data-tip="1570" target="_blank" href="/glossary-term/superior" class="glossary">superior</a> improvements in <a id="balance" data-tip="1190" target="_blank" href="/glossary-term/balance" class="glossary">balance</a> and abdominal strength (90). Another RCT by Setyawan et al. compared 90 male students (age: 17-19 years) randomly assigned to a control group (no activity), circuit training on a foam mattress group, or circuit training on a <a id="stability" data-tip="1191" target="_blank" href="/glossary-term/stability" class="glossary">stability</a> ball group. Both training groups performed exercise for 6 weeks, 3x/week, 45 minutes/session, 40-60% training intensity, 3 circuits/session, 30 sec rest between exercises, and 2 min rest between circuits. The mattress circuit included 6 stations (bridge on floor, single leg bridging, windshield wiper, <a id="unilateral" data-tip="1551" target="_blank" href="/glossary-term/unilateral" class="glossary">unilateral</a> bridge, reverse pendulum, <a id="prone" data-tip="1561" target="_blank" href="/glossary-term/prone" class="glossary">prone</a> scaption, and windshield wipers), and the <a id="stability" data-tip="1191" target="_blank" href="/glossary-term/stability" class="glossary">stability</a> ball circuit included 6 similar exercises (bridge on <a id="stability" data-tip="1191" target="_blank" href="/glossary-term/stability" class="glossary">stability</a> ball, single leg on <a id="stability" data-tip="1191" target="_blank" href="/glossary-term/stability" class="glossary">stability</a> ball, hip lift on <a id="stability" data-tip="1191" target="_blank" href="/glossary-term/stability" class="glossary">stability</a> ball, single-leg hip lift on <a id="stability" data-tip="1191" target="_blank" href="/glossary-term/stability" class="glossary">stability</a> ball, <a id="stability" data-tip="1191" target="_blank" href="/glossary-term/stability" class="glossary">stability</a> ball leg rotations <a id="stability" data-tip="1191" target="_blank" href="/glossary-term/stability" class="glossary">stability</a> ball leg rotations, <a id="prone" data-tip="1561" target="_blank" href="/glossary-term/prone" class="glossary">prone</a> scaption on <a id="stability" data-tip="1191" target="_blank" href="/glossary-term/stability" class="glossary">stability</a> ball). The findings demonstrated that the foam mattress and <a id="stability" data-tip="1191" target="_blank" href="/glossary-term/stability" class="glossary">stability</a> groups exhibited similar improvements in <a id="balance" data-tip="1190" target="_blank" href="/glossary-term/balance" class="glossary">balance</a> and flexibility; however, the <a id="stability" data-tip="1191" target="_blank" href="/glossary-term/stability" class="glossary">stability</a> ball group exhibited larger improvements in abdominal strength (91). These studies imply that the addition of <a id="stability" data-tip="1194" target="_blank" href="/glossary-term/stability" class="glossary">unstable</a> environments and loads may result in similar strength, endurance, and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> improvements, but may additionally result in <a id="superior" data-tip="1570" target="_blank" href="/glossary-term/superior" class="glossary">superior</a> improvements for <a id="balance" data-tip="1190" target="_blank" href="/glossary-term/balance" class="glossary">balance</a> and abdominal strength.
<h4>Older Adults</h4>
Studies demonstrate that the addition of <a id="stability" data-tip="1194" target="_blank" href="/glossary-term/stability" class="glossary">unstable</a> environments to circuit training for older adult exercisers may improve <a id="balance" data-tip="1190" target="_blank" href="/glossary-term/balance" class="glossary">balance</a>, strength, and some functional outcome measures. Avelar et al. compared 35 elderly women (mean age = 69.31, SD = 7.35) randomly assigned to a wait-list control group (no additional activity) or a <a id="balance" data-tip="1190" target="_blank" href="/glossary-term/balance" class="glossary">balance</a> circuit group. The circuit included 13 workout stations (multidirectional gait in different bases of <a id="base-of-support" data-tip="1197" target="_blank" href="/glossary-term/base-of-support" class="glossary">support</a>, <a id="stability" data-tip="1194" target="_blank" href="/glossary-term/stability" class="glossary">unstable</a> surfaces, functional reach, exercises with balls, and single-leg stance), progressed every 3 weeks from eyes open, to eyes closed, to obstacles and eyes open, to obstacles and eyes closed, for 12 weeks, 2x/week, 1 min at each station, approximately 1 min rest between stations, and approximately 30 minutes/session. Findings demonstrated significant improvements in knee extensor strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, static and dynamic <a id="balance" data-tip="1190" target="_blank" href="/glossary-term/balance" class="glossary">balance</a> (AccuSway Plus force platform), and function tests (Timed Up &amp; Go <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>, 30-s chair stand, and 6-min walk tests) (92). Gin&#xE9;-Garriga et al. compared 52 elderly individuals (31 women, 20 men) with markers of fragility (age: 84 &#xB1; 2.9 years) randomly assigned to a control group (no additional activity) and a circuit training group. Circuit training (combination of functional <a id="balance" data-tip="1190" target="_blank" href="/glossary-term/balance" class="glossary">balance</a> and lower body strength-based exercises) was performed for 12 weeks, 2x/week. The findings demonstrated that the circuit training group exhibited significant decreases in markers of fragility (Barthel Index Scores, rapid gait <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>, stand-up <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>), and improvements in <a id="balance" data-tip="1190" target="_blank" href="/glossary-term/balance" class="glossary">balance</a>, gait speed, isometric knee extensor strength, and self-reported health status measures (93). Although the available research lacks comparison to conventional exercise selection, the research suggests that elderly individuals performing circuit training with <a id="balance" data-tip="1190" target="_blank" href="/glossary-term/balance" class="glossary">balance</a> and <a id="stability" data-tip="1191" target="_blank" href="/glossary-term/stability" class="glossary">stability</a> exercises are likely to exhibit significant increases in strength, endurance, <a id="balance" data-tip="1190" target="_blank" href="/glossary-term/balance" class="glossary">balance</a>, and subjective health, as well as improvements in functional outcomes measures (e.g. timed up-and-go <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>, 30-s chair stand, 6-min walk <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>, rapid gait <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>, stand-up <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>, and Barthel Index Scores).
<img title="Trainer working with an older client" src="https://www.datocms-assets.com/25800/1649649545-senior-fitness.jpg" alt="An older adult working out with a trainer">

Two interesting studies investigated whether circuit training routines could be created that mimicked the physical characteristics of demanding occupations. Ouergui et al. compared 20 kickboxers (age: 21.3 &#xB1; 2.7 years) following a circuit training routine and a competitive fight. The circuit was designed to mimic fight intensity and included, punches, kicks, punch combinations, bouncing, etc. The findings demonstrated that circuit training mimicked competition based on post-session serum concentrations of growth <a id="hormone" data-tip="1266" target="_blank" href="/glossary-term/hormone" class="glossary">hormone</a>, testosterone, glucose, lactic acid, body mass changes, HR, RPE, and counter-movement jump performance (94). Abel et al. compared 20 career firefighters (age: 30.7 &#xB1; 5.8 years) following the performance of a circuit training routine with <a id="normative-data" data-tip="1508" target="_blank" href="/glossary-term/normative-data" class="glossary">normative data</a> on fire fighting activity. The circuit training routine included 12 exercises/circuit (stressing all major <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> groups), 2 circuits/session, a self-selected &quot;weight that was challenging to perform 12 reps&quot;, reps until failure/set, with 30 sec rest between exercises. Findings demonstrated the mean HR during circuit training was similar to HR data recorded for simulated smoke-diving tasks (79.4 &#xB1; 5.4 vs. 79 &#xB1; 6% max HR, p = 0.741), but lower than HR data recorded for fire suppression tasks (79.4 &#xB1; 5.4 vs. 88 &#xB1; 6% max HR, p &lt; 0.001), and post circuit training blood lactate was similar to peak blood lactate data recorded following the performance of simulated rescue tasks (11.8 &#xB1; 3.1 vs. 13 &#xB1; 3 mmol&#xB7;L&#x2212;1, p = 0.084) (95). These studies suggest that circuit training can closely mimic the anaerobic stress and physiological response correlated with fight sports and fire-fighting; however, a study comparing circuit training and fire-fighting may suggest circuit training is not ideal for matching aerobic demands.

Hydraulic/isokinetic equipment is likely a poor choice for resistance training, including circuit training. As mentioned above, Lehnert et al. compared 9 untrained women (age: 36.2 &#xB1; 9.97 years) performing a 16 exercise circuit of isokinetic equipment (concentric resistance only) and bodyweight exercises, performed for 12 weeks, 3x/week. The study demonstrated that changes in lean body mass, body fat %, and body weight were insignificant, improvements in total reps and peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> were relatively small, and the isokinetic equipment made it difficult to monitor changes in intensity (47). Another study mentioned above, Hortobagyi et al. compared 28 college males randomly assigned to control group (no additional activity), a low-resistance group, or a high-resistance training group for 13 weeks, 3x/week. The circuit training was performed on hydraulic resistive exercise equipment (7 upper and lower body, and 6 supplementary exercises). The findings demonstrated that the exercise groups did not exhibit significant changes in body fat % or circumference measurements, and both groups exhibited relatively small improvements in <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> strength, <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> endurance, and run performance (48). Last, an RCT by Stanforth et al. compared 32 healthy men and women (age: 20 - 40, average 30.6 years) divided into a control group (no additional activity), and 2 circuit training groups, using machines that allowed for concentric contractions only, or concentric and eccentric contractions. The circuit routine included 8 exercises (chest press, rows, shoulder press, lat pull downs, leg extensions, leg curls, arm curls, and arm extensions) and was performed for 12 weeks, 3x/week, 3 sets/exercise, 12 RM/set (starting with 10 reps/set at 50% of 1-RM), 3 sec/rep tempo, and 45 sec rest between sets. Findings demonstrated that both groups exhibited similar improvements in skinfold and circumference measurements, and both groups exhibited increases in strength compared to controls. Although the concentric-only group did show <a id="superior" data-tip="1570" target="_blank" href="/glossary-term/superior" class="glossary">superior</a> improvements for a few lifts, the concentric and eccentric group also showed <a id="superior" data-tip="1570" target="_blank" href="/glossary-term/superior" class="glossary">superior</a> improvements for few lifts, and the testing only included concentric contractions (96). These studies suggest that hydraulic/isokinetic equipment is a relatively poor choice for resistance training, resulting in relatively small changes in body composition, strength, endurance, and speed. Further, even when strength is tested with concentric force only, concentric only repetitions may result in <a id="inferior" data-tip="1569" target="_blank" href="/glossary-term/inferior" class="glossary">inferior</a> improvements when compared to conventional concentric and eccentric resistance training.

The following studies likely compare strength training and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training; however, the use of circuit training protocols in these studies allow us to infer that the findings can be applied to circuit training protocols.

Endurance athletes, specifically runners, may benefit more from <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training than strength training. An RCT by Taipale et al. (2013) compared 37 male recreational endurance runners (age: 21-45 years) randomly assigned to a strength group, an explosive group, a strength and explosive group, or a bodyweight circuit training group. All participants continued their endurance training and engaged in a 6-week preparatory strength training program that progressed from 50 - 70% of 1RM loads. This preparatory program was followed by the 8-week experimental condition, performed 1-2x/week, all programs included sit-ups and back extensions for 3 sets, 20-30 reps/set with bodyweight, and the strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> conditions included 2 min rest between sets. Strength training included squats and leg press performed for 3-4 sets, 4-6 reps/set, 80-85% of 1RM, calf raises for 2 sets, 12 - 15 reps/set, with 50-60% of 1-RM loads. <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training included squats and leg press with maximal tempo, 3 sets/exercise, 30-40% of 1-RM, maximal squat jumps for 2-3 sets, 5 reps/set, body weight, and maximal squat jumps for 2-3 sets, 5 reps/set, with 20 kg. The mixed <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> and strength group performed squats and leg press, 2-3 sets, 4-6 reps, 70% of 1-RM, and box jumps and vertical jumps, 2-3 sets, 8-10 reps/set with body weight. Circuit training included a series of bodyweight exercises (example: squats, push-ups, lunges, sit-ups, toe raises, back-ups, planks and step-ups) with a work:rest ratio of 45:15 sec weeks 0-4, and 50:10 weeks 4-8. The findings of the study demonstrated that strength improved in all groups; however, strength improved most for the max strength training group. Countermovement jump height improved for all groups; however, the increases were largest for the <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training and mixed groups. Max VO2 only increased for the circuit training group, and no group exhibited significant changes in body fat % or serum concentrations of testosterone, cortisol, or thyroid-stimulating <a id="hormone" data-tip="1266" target="_blank" href="/glossary-term/hormone" class="glossary">hormone</a> (97). Another study by Taipale et al. (2014) compared 34 subjects (16 men, 18 women; age: 21-45 years) performing a running program (3x/week) and 8 weeks of a preparatory phase in which both groups performed the same resistance training program (similar methodology as above), followed by random assignment to 8 weeks of a mixed strength and explosive exercise group, or a bodyweight exercise circuit group. The strength and explosive exercise routine (squat, leg press, box jump, vertical jump, sit-ups, back extensions) was performed 2x/week, 1-3 sets/exercise, 6-8 RM/set or bodyweight, with long (2-3 min) rest between sets. The body weight circuit (squats, push-ups, lunges, sit-ups, calf-raises, back extensions, planks, and step-ups) was performed 2x/week, 45:15 sec work:rest ratio for 4 weeks followed by a 50:10 sec work:rest ratio for 4 weeks. Both groups exhibited significant improvements in strength and power; however, the bodyweight circuit group did not exhibit improvements in peak running speed. The maximal and explosive exercise group exhibited larger improvements in explosive strength, maximal strength, <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> activation, and peak running speed (98). These studies suggest that compared to bodyweight circuit training, conventional max strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training result in <a id="superior" data-tip="1570" target="_blank" href="/glossary-term/superior" class="glossary">superior</a> improvements for explosive strength, maximal strength, <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> activation, jump height, and peak running speed. However, the improvements in VO2 max noted in some circuit training studies may imply that additional research should investigate the combination of strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercises performed with a circuit protocol.

Several studies were located comparing circuit training with strength or <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercise, and their effect on sprint performance. Note, the Taipale et al. study (2014) mentioned above, demonstrated that the combination of strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercises resulted in larger improvements in peak running speed (98). Bachero-Mena et al. compared 13 high-level 800 meter sprint athletes (age: 17 - 35 years) randomly assigned to a circuit training group or a high-speed resistance training group for 25 weeks. Circuit training included primarily strength exercises (half-squats, barbell step-ups, jump squats, jumps, hamstrings curls, quadriceps extensions, and calf exercises) for 3-5 sets/exercise, 10-30 reps/set, and 0-40% of 1-RM loads. High speed resistance training included mostly <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercises (squats, jump squats, resisted sprints, step phase of triple jumps) for 3-5 sets/exercise, 4-6 reps/set, and 40-55% of 1-RM loads. Findings demonstrated that both groups improved 800m sprint times; however, the high speed resistance training group also improved 200 meter sprint times, counter-movement jump height, and squat strength. Neither group exhibited a significant <a id="hormone" data-tip="1266" target="_blank" href="/glossary-term/hormone" class="glossary">hormone</a> response (99). An RCT by Maniazhagu et al. compared 30 boy students (age: 13 - 14 years) randomly assigned to a control group (no additional activity), a &quot;normal tempo&quot; circuit group, or a &quot;fast tempo&quot; circuit group. The circuit training included body weight exercises (half squats, push ups, bent-knee sit ups, two-legged low hops, back extensions, pull-ups, burpees, and shuttle runs), and progressed in volume for 6 weeks, 5 days/week, 3 circuits/session, 2:40 to 5:20 min:sec/circuit, 20-40 sec/set, and 30 sec rest between sets. The two groups only differed in rep tempo (normal tempo versus max tempo). Although both groups exhibited improvements in sprint performance, the max tempo group improved more (100, 101). Again, these studies demonstrate peak running speed and sprint times are likely to improve more following fast tempo or <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training exercises when compared to slow tempo or conventional strength training exercises.
<img title="Sprinter athletes that would benefit from power (high-intensity) circuit training programs" src="https://www.datocms-assets.com/25800/1649306258-sprinters-glutes-1.jpeg" alt="Sprinters starting at the blocks in a race">

Additional studies suggest that differences in outcomes following circuit training with <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercise or strength exercise may be related to <a id="specificity" data-tip="1223" target="_blank" href="/glossary-term/specificity" class="glossary">specificity</a>. As mentioned above, Freitas et al. compared 9 semi-professional basketball players (age: 21.44 &#xB1; 2.5 years) performing heavy-load (slower tempo) or fast tempo (lighter-load) training protocols performed in circuit (Block 1: 1/2 squats, bench press, ankle extensions; Block 2: lat pull-downs, knee flexions, elbow extensions), for 4 sets/exercise, 6 RM/set, 40 sec rest between exercises, 5 min rest between blocks, and the only difference between routines was the load and velocity of the reps. The findings demonstrated a decrease in max strength, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, agility, and shooting <a id="accuracy" data-tip="1218" target="_blank" href="/glossary-term/accuracy" class="glossary">accuracy</a> following the heavy-load training protocol, but not the fast tempo training protocol (62). Kumar et al. compared 200 female college athletes (20 each from 5 sports: volleyball, basketball, hockey, kho-kho, kabaddi, and 5 events: long jump, high jump, shot-put, discus throw, and javelin throw) performing either mixed jumping or depth jumping circuit routines for 6 weeks, 3x/week, 3 rounds/session, 6-10 reps/set (progressive increase), and a 10m jog for rest between sets. The mixed program included 5 single-leg hops/foot, 5 double-foot box jumps (25cm), 5 2-legged hurdle jumps over 5 hurdles (42cm), and 5 double-foot depth jumps (30 cm). The depth jump routine included 5 double-foot depth jumps (15cm), 5 double-foot depth jumps (25cm), 5 double-foot depth jumps (35cm), and 5 double-foot depth jumps (45cm). The findings demonstrated that both groups exhibited significant improvements in vertical jumping height and standing long-jump distance. However, the depth jump program resulted in larger improvements, and the difference was larger for event athletes (102). An RCT by Diswar et al. compared 30 school level basketball players (aged: 14-17 years) randomly assigned to a control group (no additional activity), a speed, agility, and quickness (SAQ) training group, and a circuit training group, for 12 weeks, 3x/week, and approximately 60 minutes/session. SAQ training included multi-directional movement, hand-eye coordination, <a id="balance" data-tip="1190" target="_blank" href="/glossary-term/balance" class="glossary">balance</a>, and velocity training, and circuit training included 6-8 strength training exercises performed for multiple sets. The findings demonstrated that the SAQ group exhibited larger improvements in speed and agility, and the circuit training group exhibited larger improvements in <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> endurance of the trunk and limbs (103). In summary, faster training speeds are less likely to have an immediate detrimental effect on <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, agility, and <a id="accuracy" data-tip="1218" target="_blank" href="/glossary-term/accuracy" class="glossary">accuracy</a>. Depth jumps are likely to result in larger improvements than a mixed jumping program for max jump height and distance (especially for event athletes). And, speed and agility training is likely to result in larger improvements in speed and agility, while strength training is likely to result in larger improvements in <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> endurance.

<h3>Circuit Training (Vertical Loading) compared to Conventional Strength Training (Horizontal Loading)</h3>
The research discussed in our course <a href="https://brookbushinstitute.com/courses/acute-variables-rest-between-sets" target="_blank" rel="noopener">Acute Variables: Rest Between Sets</a>, demonstrates that long (&gt; 3 min) rest between set durations are optimal for the majority of resistance training goals, likely due to the resulting increase in reps/set and exercise volume when training with reps until failure/set. These studies assume that any increase in session time is reasonable; however, nearly all exercisers (recreational to professional athletes) have limited time or would benefit from less time spent per session. This leads to the question of whether opposing or less related muscle groups, can be trained during long rest between sets, and/or if "circuit training" (sometimes referred to as "vertical loading") is a viable option to ensure optimal volume is achieved within limited session times.

Several studies have compared the physiological changes following a single session of conventional strength training or circuit training. Mar&#xED;n-Pag&#xE1;n compared 10 amateur soccer players (Age: 19&#x2013;30 years) performing either conventional or circuit training protocols during a resistance training routine (Block 1: pec deck, knee extensions, and elbow flexions; block 2: knee flexions, lat pulldowns, and ankle extensions), for 3 sets/exercise, 6-RM loads (~85&#x2013;90% of 1-RM), and a moderate tempo (3:0:1). The conventional resistance training protocol included 3-min rest between sets and 5-min rest between blocks, and the circuit training protocol included 35 sec rest between exercises and 5 min rest between blocks. The findings demonstrated that HR and VO2 were significantly higher during the circuit training session; however, circuit training time was about 35 percent less than traditional resistance training (104). M&#xE1;rquez et al. compared 12 trained men (age: 21 &#xB1; 0.8 years) performing a 3 exercise routine (back squats, upright rows, and bench press) with conventional strength training acute variables and circuit training acute variables. Conventional strength training variables included 8 sets/exercise, 6 RM/set, 155 seconds rest between sets, a moderate (3 sec/rep) tempo, and a total training time of 77 minutes. The circuit training acute variables were the same sets, load, and reps, but exercises were performed in circuit, with 35 sec rest between exercises resulting in a similar amount of time between sets of the same exercise, and the total training time was only 29 minutes. The findings demonstrated a reduction in knee extensor maximum voluntary contraction (MVC) for up to 10 minutes following the circuit training protocol; however, changes in mean and peak EMG activity during MVC were similar for both protocols. Further, resting twitch amplitude decreased and blood lactate levels were higher following the circuit training protocol. This may imply that the larger reduction in strength following circuit training is not due to central <a id="nervous-system" data-tip="1690" target="_blank" href="/glossary-term/nervous-system" class="glossary">nervous system</a> fatigue, but may be due to peripheral fatigue, and/or lactate accumulation influencing contraction-excitation coupling (105). Alcaraz et al. compared 10 resistance trained men (age: 26 &#xB1; 1.6 years) performing bench press, or bench press during a heavy resistance training circuit, on separate days. The bench press day included bench press for 5 sets, reps until failure/set, 6 RM load, long (3 min) rest between sets, and a moderate tempo (3:0:maxV), and the heavy circuit training day included bench press, leg extensions, ankle extensions for 5 sets/exercise, reps until failure/set, 6 RM loads, short (35 sec) rest between exercises, 3 min of active rest between circuits, and a moderate tempo (3:0:maxV). The findings demonstrated that despite HR being higher during heavy circuit training, both groups performed the bench press exercise with a similar number of reps/set, peak and average bar velocity, and peak and average <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> (106). Deminice et al. compared 11 resistance-trained male participants (age: 25.9 &#xB1; 2.8 years) performing a strength training routine of 6 exercises (bench press, leg extensions, cable pull downs, leg flexions, overhead press, and leg press) with either a conventional resistance training protocol of 3 sets/exercise, 10 reps/set, 75% of 1-RM loads, and moderate (90 sec) rest between sets, or a circuit resistance training protocol of 3 sets/exercise, 10 reps/set, 75% of 1-RM loads, with no rest between 2 exercises for different muscles. The findings demonstrated that both protocols resulted in a similar number of reps/set, total exercise volume, blood lactate, and RPE, despite circuit training taking half the time (20 min compared to 40 min), and resulting in higher peak and average HR during training. Note, the conventional training protocol resulted in higher post-exercise serum concentrations of thiobarbituric acid reactive substances (TBARSs), glutathione, creatine kinase, and uric acid (107). These studies demonstrate that during a session, circuit training results in higher peak HR, average HR, and peak O2 consumption, but a similar number of reps/set (exercise volume), peak and average bar velocity, and peak and average <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>. Further, circuit training protocols may reduce session time by 35 - 60 percent. Immediately post circuit training a larger reduction in MVIC may be exhibited; however, studies demonstrate <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> activity is similar, implying the decrease may be due to peripheral fatigue (lactate accumulation). Last, post-exercise serum concentrations of thiobarbituric acid reactive substances (TBARSs), glutathione (GSH), creatine kinase (CK), and uric acid may be higher following conventional strength training protocols; however, as discussed in several of our reviews/courses, this may have no influence on long-term outcomes.

Research has compared outcomes following several weeks of strength training with conventional protocols and long (&gt; 3 min) rest between sets, and circuit training protocols with short (30 - 60 sec) rest between exercises. Another RCT by Alcaraz et al. (2011) compared 38 resistance trained men (age: 22.7 6 3.3 years) randomly assigned to a control group (no additional activity), a conventional strength training group, or a circuit training group. The exercise protocols included 6 exercises (Block 1: pec deck, knee extensions, elbow flexions; block 2: knee flexions, lat pulldowns, and ankle extensions) for 8 weeks, 3x week, 3-6 sets/exercise, 6-RM loads (~85&#x2013;90% of 1-RM), and a moderate tempo (3:0:1). The conventional resistance training protocol included 3-min rest between sets and 5-min rest between blocks, and the circuit training protocol included 35 sec rest between exercises, and 5 min rest between blocks. Research demonstrated that improvements in lean body mass, 1-RM strength, peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, and shuttle run performance were similar for both groups (80). Johnson et al. compared 39 high school football athletes (age: 16 &#xB1; 2 years) randomly assigned to a conventional protocol group, or a circuit protocol group, using the same routine. The routine included Olympic lifts and strength exercises (e.g. Day 1: hang clean, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> jerk, bench press, dumbbell split squat, inverted rows) performed for 6 weeks, 3x/week, 3 sets/exercise, 8 reps/sets, with rest between sets not tightly controlled. Note, both groups performed hang-cleans prior to the rest of the routine for 3 - 5 sets/session, 1-5 reps/set, with conventional rest between sets. The findings demonstrated that the groups were not equal at the beginning of the training program; however, it is likely both protocols had similar efficacy for improving strength, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, and agility. Due to the circuit group starting with more strength and making similar improvements, it may be hypothesized that the circuit protocol was more effective (108). As mentioned above, Balachandran et al. compared 21 sarcopenic obese adults (age: 60 - 90 years) randomly assigned to a conventional resistance training group or a circuit training group, for 15 weeks, on 11 machines targeting major <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> groups. The findings demonstrated that the circuit training group exhibited larger improvements for lower body <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> and the Short Physical Performance Battery (SPPB); however, improvements in the Instrumental Activities of Daily Living (IADL), Skeletal <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> Index (SMI), and body fat % were similar for both groups (52). These studies suggest that conventional resistance training protocols (long rest between sets) and circuit training protocols (short rest between exercises) are likely to result in similar improvements in lean body mass, maximum strength, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, and agility following 6 - 15 weeks of training. However, circuit training may result in some additional functional benefits (improvement of SPBB scores) for older adults.

The effects of conventional, circuit training and aerobic training on VO2 max have been compared in a few studies. Messier et al. compared 36 male college students, who had not engaged in a running or resistance training program in the previous 4 months, following performance of a Nautilus machine circuit, conventional resistance training, or a running program for 10 weeks, 3 days/week. The Nautilus machine circuit included 12 exercises (hip and back, leg extensions, leg press, leg curls, pullovers, torso arms, chest flyes, decline press, <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> raises, shoulder press, bicep curls, and triceps extensions), for 1 set/exercise, 8-12 reps until failure/set for upper body, 15-20 reps until failure/set for lower body, and no rest between exercises. The conventional resistance training program included 8 exercises (squats, stiff-legged deadlifts, lunges, bent-over rows, chest flyes, bench press, military press, bicep curls, and triceps extensions), for 3 sets/exercise, 6 reps/set, 75% of 1-RM loads, and 15/30s work:rest ratio. And, the running program was performed for approximately 30 min/session, with a progressive increase in intensity, and 60-90% of HR reserve. The findings demonstrated that circuit training and conventional resistance training resulted in similar increases in VO2 max and strength; however, the largest improvements in VO2 max were achieved with the running program (109). An RCT by Brentano et al. compared 28&#xA0;postmenopausal women randomly assigned to a control group (no additional activity), a conventional strength training group, or a circuit training group. The exercise groups included training for&#xA0;24 weeks, 3 x/week, with a linear increase in loads (1-RM tested every 8 weeks), and similar routines (alternating upper and lower body exercises including leg press, hip abductions, hip adductions, knee extensions, chest flyes, reverse flyes, arm curls, triceps push-downs, sit-ups, and back extensions). The circuit training protocol included 10-20 reps/set, 45-60% of 1-RM loads, 2-3 sets/exercises, and no rest between exercises; the strength training protocol included 6-20 rep/set, 45-80% of 1-RM loads, 2-4 sets/exercise, and moderate (2 min) rest between sets. The findings demonstrated that the traditional strength training and circuit training protocols resulted in similar increases in VO2 max, similar maintenance of bone mineral density, and significant increases in <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> strength and endurance. The strength training protocol resulted in slightly larger increases in lower body strength and EMG activity following training; however, the strength training protocol also included high load sets (110). These studies suggest that circuit training and conventional resistance training result in similar improvements in VO2 max, and that these improvements are likely <a id="inferior" data-tip="1569" target="_blank" href="/glossary-term/inferior" class="glossary">inferior</a> to a progressive aerobic training program. Note, several studies mentioned above comparing conventional training and circuit training, without the addition of aerobic training, imply circuit training results in slightly <a id="superior" data-tip="1570" target="_blank" href="/glossary-term/superior" class="glossary">superior</a> benefits for cardiovascular performance.

Two studies were located comparing caloric burn and body composition following conventional strength training and circuit training. An RCT by Romero-Arenas et al. compared 37 healthy men and women (61.6&#xB1;5.3 years) randomly assigned to a control group (no additional activity), a conventional strength training group, or a heavy-load circuit training group. The exercise groups trained for 12 weeks, 2x/week, with 1-3 sets/exercise. Conventional strength training included 3 exercises (leg curls, pec deck, seated calf raises) with 2 warm-up sets (12 reps at 50% of 6-RM, 10 reps at 75% of 6RM), followed by 1-3 sets/exercise, 6 RM/set, with 3 min rest between sets, and a moderate tempo (3 sec eccentric), this was followed by a 5 min rest and a second set of exercises using the same protocol (seated pulley rows, leg extensions, and preacher curls). The circuit training group used the same parameters, but performed each block of 3 exercises in a circuit with 35 sec rest between exercises and 5 min rest between blocks of exercises. The findings demonstrated that circuit and conventional strength training resulted in similar improvements in strength; however, the circuit training group exhibited <a id="superior" data-tip="1570" target="_blank" href="/glossary-term/superior" class="glossary">superior</a> improvement in body composition (decreased body fat and increased lean mass) and cardiovascular performance (incremental treadmill <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>) (55). Murphy et al. compared 10 untrained men (age: 23.6 &#xB1; 3.9 years) performing circuit or conventional resistance training protocols. Both routines included the same exercises (<a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> cleans, bench press, squats, bicep curls, seated military press, and bent knee sit-ups), the resistance training protocol included 3 sets/exercise, 12, 10, and 8 reps/set, 80% of 1-RM loads, moderate (2 min) rest between sets, and took 50 minutes to complete. The circuit training protocol included 3 sets/exercise performed in circuit, reps until failure/set, 50% of 1-RM, 30 sec rest between exercises, and took 19 minutes. The findings demonstrated that EPOC lasted for approximately 20 minutes and burned an additional 24.9 calories following the circuit training protocol, and lasted approximately 15 minutes and burned 13.9 calories following the conventional resistance training routine (41). These studies suggest that performing conventional strength training in circuit may result in a small but significant increase in caloric burn, body composition, and cardiovascular performance.

<h4>Aerobic Training or Strength Training First?</h4>
A few studies have compared outcomes following training with various orders of aerobic and resistance exercise during circuit training. Vasconcelos et al. compared 14 trained males (age: 25.7&#x202F; &#xB1; &#x202F;4.4&#x202F; years) following two exercise protocols that included both circuit training and high intensity interval running, and were matched for volume and recovery periods. Both routines included a combination of 6 bouts of high-intensity interval running (HIIT) with 15 sec run/45 sec recovery (1:3 work:rest ratio), and a 9 exercise circuit (squats, rows, planks, presses, trap bar deadlifts, crunches, sumo squats, lat pull downs, and lumbar extensions), for 10-15 reps in 30 sec/set, and 30 sec rest between sets (work:rest ratio of 1:1). The first routine started with 6 bouts of HIIT followed by 3x through the circuit, the second routine performed the 9 exercises as 3 mini-circuits of 3 exercises, 3 sets/circuit, with the bouts of HIIT performed between the mini-circuits. The findings demonstrated that the routine starting with 6 bouts of HIIT resulted in higher HR, lactate accumulation, VO2, energy expenditure, and EPOC; however, the difference in energy expenditure (including session and EPOC) was only 20 calories (average). Further, more research is needed to determine the effect of these exercise orders on strength and reps/set (38). Two publications by Chtara et al. (2005, 2008) compared 48 physical-education students (age: 21.4 &#xB1; 1.3 years) randomly assigned to 5 groups: control (no additional activity), run training alone, circuit training alone, run before circuit training, and circuit before run training. Resistance training included strength endurance training for 6 weeks followed by explosive strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training for 6 weeks. Run training sessions included 5 reps of running at approximately 50% of VO2 max for half the duration to exhaustion, followed by equal rest. The findings from the 2005 study demonstrated that running before circuit training resulted in the largest improvements in 4km time, and the findings from the 2008 study demonstrated that resistance training alone resulted in the largest improvements in 1RM strength and jump <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a> performance. Conversely, the findings from the 2008 publication reported an insignificant difference between training groups that included both aerobic and resistance training (22, 23). These studies likely suggest that the order of aerobic and strength training exercises only results in small differences; however, if cardiovascular performance or total caloric expenditure is the priority, aerobic training should be performed first, and if strength is the priority it may be advised to perform strength training alone.
<h4>Order of Resistance Training Exercises:</h4>
Two studies compared the effects of the order of resistance training exercises within a circuit training program. Cardozo et al. compared 30 untrained older women (age: 64.7 &#xB1; 10 years) performing a circuit in order and reverse order (leg press, wide-grip latissimus pull-downs, knee extensions, pec-dec flyes, plantar flexion, and triceps extensions) for 12 weeks, 2x/week, 3 sets/exercise, 8-10 reps/set, 70% of 10-RM, with 2 min rest between exercises. The findings demonstrated that more reps/set were performed for exercises at the beginning of the routine (111). Da Silava et al. compared 8 untrained females (age 23.5 &#xB1; 1.85) performing circuits in a upper/lower order (upper/lower order: bench press, leg press, high rows, knee extensions, pectoral flyes, knee flexions, and back flyes), or a pre-exhaustion order (&quot;pre-exhaustion&quot; order: bench press, pec flyes, leg press, knee extensions, knee flexions, high rows, and back flyes) for 3 circuits/session, 12 reps/set, 50-55% of 1-RM loads, with a moderate tempo (2:0:2), and no rest between exercises or circuits. The findings demonstrated that exercise order had no effect on excess post-exercise oxygen consumption or energy expenditure (112). These studies suggest that exercises programmed at the beginning of a routine are likely to be performed with more reps/set, and there is little difference in caloric burn between upper/lower routines (peripheral heart action) and pre-exhaustion routines (compound movement followed by single joint exercise).
<img alt="A lateral pulldown which includes downward rotation of the scapula" title="An example of a lateral pulldown, notice the scapular positioning during the motion" src="https://www.datocms-assets.com/25800/1647308412-istock-638231726.jpg">

<h4>Comparing Rest Between Exercises</h4>
One study was located comparing the amount of rest between exercises during circuit training. Gordon et al. compared 12 physically active men (age: 28&#xA0;&#xB1; 5 years) performing two protocols with different rest between set durations, and different volumes, but performed in the same total time. The 1st protocol included 30 sec/set, 30 sec rest between stations, and 3 circuits/session in 21 minutes, and the 2nd protocol included 30 sec/set, 60 sec rest between sets, and 2 circuits/session. Both routines were performed in 21 minutes with 7 hydraulic machines (concentric resistance only: <a id="unilateral" data-tip="1551" target="_blank" href="/glossary-term/unilateral" class="glossary">unilateral</a> elbow flexion/extensions, bench press/horizontal rows, <a id="unilateral" data-tip="1551" target="_blank" href="/glossary-term/unilateral" class="glossary">unilateral</a> knee extension/flexions, shoulder press/lat pull downs, squats, pec flyes/reverse flyes, seated leg abduction/adductions). The findings demonstrated that an average of 35% more reps were completed during the 30 sec rest between sets group; however, an average of 9% more reps/set were completed by the 60 sec rest between sets group. Additionally, the 30 sec rest between sets group exhibited higher average oxygen uptake, energy expenditure and HR. This study demonstrates several relationships between&#xA0;rest between exercises, reps/set, sets/session, and exercise volume during circuit training when session time is equal. Although more reps/set may be performed with longer rest between exercises (60 sec vs. 30 sec), these benefits should be compared to the potential for more sets performed during a session with a fixed duration.
<h4>Increased strength, no decrease in ROM</h4>
Monteiro et al. compared 20 women (age: 37 &#xB1; 1.7 years) randomly assigned to a control group (no additional activity) or a circuit training group. Circuit training included a total body circuit (flat bench press, smith machine squats, lat pull-downs, 45&#xB0; leg press, 30&#xB0; inclined bench press, hack squat machine, and abdominal crunches) for 10 weeks, 3x/week, 3 circuits/session, 8-12 RM/set, except for abdominal exercise performed with 15-20 RM/set, with a 1:3 work:rest ratio, and 2 min rest between circuits. The findings demonstrated that circuit training resulted in significant improvements in strength, and no decrease in flexibility for any of the 10 range of motions tested (including shoulders, hips, and spine). This study provides strong evidence that resistance training, and specifically circuit training, do not decrease flexibility.
<h4>Hypoxic Versus Normoxic Environments</h4>
A group of 4 RCTS (or 4 publications based on the same or similar experiments) by the same group, compared heavy circuit training with normal (normoxic) and decreased (hypoxic) oxygen environments. An RCT by Ramos-Campo et al. (2017) compared 20 resistance-trained male subjects (age: 25.1 &#xB1; 4.8 years) in normoxic and hypoxic conditions performing high load circuit training (Circuit 1: bench press, deadlifts, preacher curls; Circuit 2: half squats, french press, calf raises), 2 circuits/session, 3 sets/exercise, 6 reps/set, 6-RM loads, 35 sec rest between exercises, 3 min rest between cycles, and 5 minutes rest between circuits. The findings demonstrated that high hypoxia (FiO2 = 0.13; 3.800 m altitude) resulted in higher energy consumption for 20 min following training, a significant decrease in mean and maximum forces during bench press, no change in jump performance or HR, and a significant increase in the RPE (115). 3 additional publications by Ramos-Campo et al. compared 28 resistance-trained male subjects (age: 24.6 &#xB1; 6.8 years) during normoxic and hypoxic conditions performing high load circuit training (block 1: bench press, leg extensions, and front lat pulldowns; block 2: deadlifts, elbow flexions, and ankle extensions), for 8 weeks, 2x/week, 2 circuits/session, 3 sets/exercise, 6 reps/set, 6-RM loads, 35 sec rest between exercises, 3 min rest between cycles, and 5 minutes rest between circuits (81, 82, 116). The publication by Ramos-Campo et al. (2018) demonstrated that the hypoxic group exhibited significantly larger improvements in repeated sprint performance with a decrease in RPE (116). The publication by Ramos-Campo et al. (2021) reported both groups exhibited similar improvements in <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> thickness, pennation angle (quadriceps), maximum voluntary isometric contraction, rate of force development, peak force development, and max HR (81). And, an additional publication by Mart&#xED;nez-Guardado et al. (same group) (2019) reported that lean body mass and bone mineral density increased significantly for the hypoxic group, but statistical significance was not reached by the normoxic group (82). These studies likely imply that a hypoxic environments may result in an acute decrease in strength training performance, an increase in caloric expenditure immediately following training, and may result in some long-term benefits for cardiovascular performance variables. However, the difference between improvements made for strength and hypertrophy following training in hypoxic and normoxic environments are likely small, if there is any difference at all.
<h4>Skin Temperature</h4>
Viera et al. compared 16 male and female adults (age: 24.56 &#xB1; 3.22 years) performing a resistance training circuit (lat pull-downs, leg presses, and biceps curls) for 3 sets/exercise, 12 reps/set, with 70 - 80% of 1-RM loads. The findings demonstrated that resting skin temperature was higher for men than women, circuit training did not have a significant effect on average skin temperature 20 min post-exercise; however, skin temperature was elevated in the upper back of men and quadriceps of women 24 hours post-exercise (117). Additional research may be recommended to determine whether skin temperature is correlated with caloric expenditure and/or area-specific fat metabolism.
<h4>Altered Muscle Activity</h4>
Jeong et al. compared 25 females (age:&#xA0;24.0 &#xB1; 2.0 years) randomly assigned to a control group (no additional activity) or a circuit training group (combination of strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercises). Circuit training included 9 exercises (leg press, leg extensions, leg curls, lat pull downs, shoulder press, chest press, leg raises, crunches, and barbell squats), was performed for 10 weeks, 3x/week, 50 min/session, and progressed in 2 phases. Phase 1 was performed for 5 weeks, 3 circuits/session, 12 reps/exercise, 60% of 1-RM loads, with a slow (2:1:2) tempo, and a moderate (1 min) rest between exercises, followed by phase 2 for 5 weeks, 3 circuits/session, 20 reps/exercise, 30-45% of 1-RM loads, with a fast (1 sec/rep) tempo. The findings demonstrated that circuit training resulted in an increase in quadriceps and hamstrings strength. Further, during a side-stepping cutting maneuver, the circuit training group exhibited an altered activation ratio of the quadriceps/hamstrings, decreased gastrocnemius activity during the pre-activation phase, without significant changes in lower extremity kinematics (functional valgus and <a id="anterior" data-tip="1566" target="_blank" href="/glossary-term/anterior" class="glossary">anterior</a> <a id="glide" data-tip="1817" target="_blank" href="/glossary-term/glide" class="glossary">shear</a> force) (118). This study implies that circuit training may have a positive effect on <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> strength and recruitment patterns during sports/daily activity.

Bibliography

&copy; Brent Brookbush 2022
Questions, comments and criticisms welcomed and encouraged.

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.

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