Terminology

Co-Contraction

Stretch Shortening Cycle

Fiber Types Proportion and Rate of Force Delvelopment

Changes in Fiber Type Proportion from Training

More Complex than Type IIX

Muscle Architecture and Power

Hormones, Enzymes and Power

Relationship Between Strength and Power

Strength Training for Power

Power Training for Power

Adaptations to Power Training

Comparing Power Training and Strength Training for Improving Power

Combining Strength and Power Training for Improving Power

Intensity (Load)

Volume (Repetition Range)

Why Not Olympic Lifts

Lower Body Progressions

Upper Body Progressions

Practical Application Summary

Training Types

Acute Variables

Training Guidelines, Acute Variables and Progressions

Power and Torque

Force Velocity Curve

Rate Coding

Power and an Increase in EMG Activity

Power (High-velocity) Training: Introduction

CanFitPro

NASM

PACE

REPSI

AFAA

PTAGlobal

AOTA

ACSM

CIMSPA

TPTA

ISSA

AUSactive

AUSPHYSIO

NYPT

WITS

This course discusses <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training, which could be viewed as a type of strength training (a.k.a. weight training, resistance training, strength workout) specifically designed to improve activities that require high velocity or maximal speed. For example, a <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training routine may be designed to improve vertical jump height, and may not be beneficial for improving 1-repetition maximum strength during a back squat.
A comprehensive systematic research review is included in this course, detailing the neural adaptations, <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> adaptations (morphological changes), effect on short and long-term <a id="hormone" data-tip="1266" target="_blank" href="/glossary-term/hormone" class="glossary">hormone</a> concentrations, comparisons between strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training, and <a id="evidence-based-practice" data-tip="1538" target="_blank" href="/glossary-term/evidence-based-practice" class="glossary">evidence-based</a> recommendations for acute variables (reps, intensity, frequency, volume, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> <a id="specificity" data-tip="1224" target="_blank" href="/glossary-term/specificity" class="glossary">specific</a> cues) and programming. Some findings from the included systematic review resulted in counter-intuitive, or at least less conventional recommendations. For example, the use of bodyweight resistance during many exercises may be more beneficial than barbell-loaded variations, and there is research to suggest that Olympic lifts are not ideal for <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training.&#xA0;
Movement professionals (personal trainers, fitness instructors, physical therapists, athletic trainers, massage therapists, chiropractors, occupational therapists, etc.) should consider <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training a pillar of athletic performance training, and potentially beneficial for fitness and rehabilitation programs. This course is part of our continued effort to optimize, <a id="evidence-based-practice" data-tip="1538" target="_blank" href="/glossary-term/evidence-based-practice" class="glossary">evidence-based</a> &#x201C;exercise program design&#x201D; recommendations.
<h3>Additional Courses:</h3>
<ul>
 <li><a href="https://brookbushinstitute.com/courses/power-training-lower-body-exercises">Power Training: Lower Body Exercises</a></li>
 <li><a href="https://brookbushinstitute.com/courses/power-training-upper-and-total-body">Power Training: Upper Body and Total Body Exercises</a></li>
</ul>
<h3>Some Helpful Definitions for Learning about Power Training</h3>
<ul>
 <li>Power - &#x201C;How fast did you work?&#x201D;, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">Power</a> = Force x Distance/Time. In health and human performance <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">Power</a> most often refers to high-velocity activity.</li>
 <li>Force-velocity curve - The force-velocity curve expresses the relationship between the amount of force a <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> can generate and the velocity of the moving joint. Generally, an increase in peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> will result in a shift up and to the right of the force/velocity curve, representing a significant increase in the rate of force development (RFD).</li>
 <li>Amortization phase - The transitional phase between eccentric and concentric contractions. For example, during a counter movement jump (CMJ), the initial quick descent and backswing of the arms would be the eccentric phase, and the bottom position would be the <a id="amortization-phase" data-tip="1546" target="_blank" href="/glossary-term/amortization-phase" class="glossary">Amortization phase</a>. Generally, the focus is placed on shortening the <a id="amortization-phase" data-tip="1546" target="_blank" href="/glossary-term/amortization-phase" class="glossary">Amortization phase</a> during training.</li>
 <li>Stretch Shortening Cycle (SSC) - A successive combination of eccentric and concentric action; resulting in more <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> generated during the concentric action than would be generated if the concentric action was performed alone. Research suggests high-velocity SSC contractions start with a forceful eccentric lengthening of <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> fibers while EMG activity increases, followed by a period of near isometric contraction of the activated <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> fibers while the tendon continues to lengthen, followed by shortening of both the tendon and the <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> complex during the concentric contraction.</li>
</ul>
<h3>Brookbush Institute Position Statement for Power Training</h3>
A combination of max strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training is likely ideal for improving high-velocity activity performance. When training specifically for <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> (maximum velocity and speed), repetition velocity is the most important acute variable. Repetitions should include a stretch-shortening cycle and a force-velocity curve that is analogous to the activities being trained for. Generally, this implies that <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training repetitions should include a quick eccentric load, an <a id="amortization-phase" data-tip="1546" target="_blank" href="/glossary-term/amortization-phase" class="glossary">amortization phase</a>, a follow-through (no deceleration to stay on the ground or hold on to an object), and soft catches and landings. Load should be limited to the amount of resistance that can be used without decreasing velocity. Research implies that ideal acute variable recommendations for <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercise are 3-5 sets/muscle group and 3-10 repetitions performed until velocity decreases/set.

Course Description: Power Training

Introduction: Power Training

<h3>Brookbush Institute Position Statement for Power Training</h3>
A combination of max strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training is likely ideal for improving high-velocity activity performance. When training specifically for <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> (maximum velocity and speed), repetition velocity is the most important acute variable. Repetitions should include a stretch-shortening cycle and a force-velocity curve that is analogous to the activities being trained for. Generally, this implies that <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training repetitions should include a quick eccentric load, an <a id="amortization-phase" data-tip="1546" target="_blank" href="/glossary-term/amortization-phase" class="glossary">amortization phase</a>, a follow-through (no deceleration to stay on the ground or hold on to an object), and soft catches and landings. Load should be limited to the amount of resistance that can be used without decreasing velocity. Research implies that ideal acute variable recommendations for <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercise are 3-5 sets/muscle group and 3-10 repetitions performed until velocity decreases/set.
<h3>Evidence-based Power Training Recommendations</h3>
<h3>Choosing Phases:</h3>
<ul>
 <li>Strength Training: Moderate load strength training may be beneficial (especially in novice lifters); however, incorporating near maximal loads is likely ideal for <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> development.</li>
 <li>Power Training: Power training is likely more beneficial than strength training for improving high-velocity tasks, especially for individuals with training experience.</li>
 <li>Combined Training: The combination of strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training is likely more beneficial than either strength or <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training alone; however, the amount of high-velocity activity already included in sport and/or practice must be considered.</li>
</ul>
<h3>Acute Variables:</h3>
<ul>
 <li>Volume: 3 - 5 sets</li>
 <li>Repetitions (reps): 3 - 10 reps/set (failure is a reduction in velocity)</li>
</ul>
<h3>Loading:</h3>
<ul>
 <li>Max Velocity: As much load as can be moved with max velocity. </li>
 <li>Eccentric Load: Always include a quick eccentric contraction. Increasing eccentric demand is appropriate for progressing <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercise (e.g. higher depth jump). </li>
 <li>Amortization phase: NEVER purposefully allow weights to touch the floor, bounce off racks, or allow a pause during this phase of a <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercise (and, it is also not recommended during strength training for <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> athletes). A goal of <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training should be to shorten the <a id="amortization-phase" data-tip="1546" target="_blank" href="/glossary-term/amortization-phase" class="glossary">amortization phase</a> as much as possible. </li>
 <li>Concentric Load: Ensure any <a id="exercise-progression" data-tip="1182" target="_blank" href="/glossary-term/exercise-progression" class="glossary">progressions</a> that involve an increase in load do so during the earliest part of the concentric contraction. Increasing load at the end of a contraction with apparatus like bands and chains is not likely to have a positive impact on the force/velocity curve of <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercise.</li>
 <li>Quick Intent: Research has demonstrated that repeated attempts with the intent to produce force quickly may be more important to developing force than the actual shortening and lengthening of the musculotendinous unit.</li>
 <li>Follow Through: Following all the way through (letting go, leaving the ground, etc.) is likely to result in greater EMG activity, better kinematics, and larger improvements from training.</li>
 <li>Soft Landing/Catching: Softer landing/catching reduces reaction forces, largely by increasing the amount of joint motion (excursion), which may reduce the wear and tear inherent in high-intensity training.</li>
</ul>

Position Statement and Practical Application

<ul>
 <li>Power - &#x201C;How fast did you work?&#x201D;, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">Power</a> = Force x Distance/Time. In health and human performance <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">Power</a> most often refers to high-velocity activity.</li>
 <li>Torque - Force applied to a lever that moves in a circle (arc) around an axis.</li>
 <li>Force-velocity curve - The force-velocity curve expresses the relationship between the amount of force a <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> can generate and the velocity of the moving joint. Generally, an increase in peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> will result in a shift up and to the right of the force/velocity curve, representing a significant increase in the rate of force development (RFD).</li>
 <li>Rate of Force Development (RFD) - The speed at which force and velocity develop, i.e. acceleration. This is a key factor in all high-velocity activities.</li>
 <li>Counter-movement Jump (CMJ) - A jump that starts with a counter-movement; that is, a forceful quick descent and backswing of the arms (eccentric phase), followed by the shortest possible time in the bottom position (<a id="amortization-phase" data-tip="1546" target="_blank" href="/glossary-term/amortization-phase" class="glossary">amortization phase</a>), followed immediately by a forceful upward jump (concentric phase). This is the jumping motion most commonly associated with a vertical jump <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>.</li>
 <li>Amortization phase - The transitional phase between eccentric and concentric contractions. For example, during a counter movement jump (CMJ), the initial quick descent and backswing of the arms would be the eccentric phase, and the bottom position would be the <a id="amortization-phase" data-tip="1546" target="_blank" href="/glossary-term/amortization-phase" class="glossary">Amortization phase</a>. Generally, the focus is placed on shortening the <a id="amortization-phase" data-tip="1546" target="_blank" href="/glossary-term/amortization-phase" class="glossary">Amortization phase</a> during training.</li>
 <li>Rate Coding (a.k.a. &quot;frequency coding) - As the intensity of a stimulus increases, the rate or frequency of action potentials increases.</li>
 <li>Stretch Shortening Cycle (SSC) - A successive combination of eccentric and concentric action; resulting in more <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> generated during the concentric action than would be generated if the concentric action was performed alone. Research suggests high-velocity SSC contractions start with a forceful eccentric lengthening of <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> fibers while EMG activity increases, followed by a period of near isometric contraction of the activated <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> fibers while the tendon continues to lengthen, followed by shortening of both the tendon and the <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> complex during the concentric contraction.<a href="https://brookbush.s3.us-east-2.amazonaws.com/wordpress/wp-content/uploads/2020/07/Box-Jump-Mike.png" target="_blank" rel="noopener"><img title="Dr. Brent Brookbush instructing the box jump exercise" src="https://www.datocms-assets.com/25800/1649513015-box-jump-mike-1.png" alt="A box jump, which is used as a lower body &lt;a id=" power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercise&quot;&gt;</li>
</ul>

Summary of Research Review

<h3>Neural Adaptations:</h3>
<ul>
 <li>Rate Coding and Rate of Force Development (RFD) - High velocity contractions result in large bursts of activity (increased discharge frequency of action potentials) that may alter the order in which clusters of motor units are recruited, likely in an attempt to access more or larger motor units, faster. An increase in <a id="rate-coding" data-tip="1293" target="_blank" href="/glossary-term/rate-coding" class="glossary">Rate Coding</a>, including motor units discharging &quot;doublets&quot; is associated with increases in RFD and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>.</li>
 <li>Increase in EMG Activity - Increases in <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> following training are strongly correlated with an increase in RFD resulting from a significant increase in EMG activity, especially during the earliest part of a concentric contraction (force-velocity curve).</li>
 <li>Motor Unit Recruitment Threshold and Ca2+ <a id="sensitivity" data-tip="1226" target="_blank" href="/glossary-term/sensitivity" class="glossary">Sensitivity</a> - The increase in <a id="motor-unit" data-tip="1303" target="_blank" href="/glossary-term/motor-unit" class="glossary">Motor Unit</a> recruitment associated with <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training is due in part to an increase Ca2+ <a id="sensitivity" data-tip="1226" target="_blank" href="/glossary-term/sensitivity" class="glossary">Sensitivity</a>. This increased <a id="sensitivity" data-tip="1226" target="_blank" href="/glossary-term/sensitivity" class="glossary">Sensitivity</a> is likely due to an increase in the proportion of type II fibers which are more <a id="sensitivity" data-tip="1227" target="_blank" href="/glossary-term/sensitivity" class="glossary">sensitive</a> to Ca2+ than type I fibers, as well as increases in membrane potential, SR total volume, SR Ca2+ <a id="release" data-tip="1249" target="_blank" href="/glossary-term/release" class="glossary">release</a>, Ca2+ uptake, Ca2+-ATPase activity, and peak Ca2+ activated force.</li>
 <li>Co-contraction - <a id="antagonists" data-tip="1705" target="_blank" href="/glossary-term/antagonists" class="glossary">Antagonist</a> co-contraction increases with RFD; however, training and experience may decrease <a id="antagonists" data-tip="1705" target="_blank" href="/glossary-term/antagonists" class="glossary">Antagonist</a> co-contraction via peripheral and CNS mechanisms to improve concentric force production and performance.</li>
 <li>Pre-stretch - A quick increase in eccentric force (pre-stretch) that results in higher concentric force production when compared to concentric contractions without pre-stretch at all loads and velocities. These studies demonstrate that the increase in concentric force from SSC contractions is likely due to neuromuscular reflex initiated by a significant preload that increases concentric EMG activity, as well as contributions from the elastic potential of lengthened myofascial tissue.
 <ul>
 <li>Tendon Stiffness: <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">Power</a> athletes may exhibit more <a id="elasticity-2" data-tip="1307" target="_blank" href="/glossary-term/elasticity-2" class="glossary">elasticity</a> at low loads; however, increased tendon stiffness at higher loads is correlated with higher RFD and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">Power</a> performance. Note, studies to date have not demonstrated that <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">Power</a> training results in acute changes in tendon stiffness.</li>
 </ul>
 </li>
</ul>
<h3>Muscle Fiber Adaptations:</h3>
<ul>
 <li>Fiber Type Proportion and RFD - Performance of high velocity movement is correlated with an increase in type II fiber proportion and CSA, and power-trained athletes may exhibit significantly higher proportions of type IIx fibers specifically.</li>
 <li>Cross-Sectional Area (CSA) - Improvements in performance following <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training are highly correlated with increased <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> CSA.</li>
 <li>Changes in Fiber Type Proportion - Endurance training or strength training done alone may shift fiber type proportion away from type I and IIx fibers, increasing the number and CSA of IIa fibers. These studies suggest that high velocity, <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> or ballistic training alone, or in conjunction with strength training may result in an increase, or aid in maintaining type IIx fiber proportions, as well as increasing the CSA of all fiber types.</li>
 <li>More Complex than Type IIx Fibers - Although maintenance of type IIx fibers may be <a id="optimal" data-tip="1571" target="_blank" href="/glossary-term/optimal" class="glossary">optimal</a> for maximizing <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, an increase in type IIa fiber CSA and proportion is more likely to follow the training, especially in sports requiring a mix of endurance, strength, and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>. Further, an increase in type IIx fiber proportions is an adaptation noted after detraining (more than 2 weeks), implying that a high proportion of type IIx fibers may also be correlated with deconditioning.</li>
 <li>Muscle Architecture - These studies demonstrate that pennation angle, when grouped with CSA and fascicle length, has a correlation with performance. However, pennation angle alone likely has little or no correlation with performance. Based on the current available evidence, it seems likely that CSA is strongly correlated with performance and that increases in CSA (hypertrophy) may incidentally alter pennation angle, and/or fascicle length.</li>
</ul>
<h3>Hormones and Enzymes:</h3>
<ul>
 <li>Enzymes and Gene Expression: <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">Power</a> training is likely to have an effect on enzyme levels (increased phosphorylase, decreases in citrate synthase), and may have an effect on hypertrophy-related gene expression (strength training results in more hypertrophy related gene-expression).</li>
 <li>Effect on <a id="hormone" data-tip="1266" target="_blank" href="/glossary-term/hormone" class="glossary">Hormone</a> Levels: <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">Power</a> training may have an acute effect on circulating testosterone; however, these changes do not seem to influence improvements in RFD. However, the resting and/or mean levels of testosterone of an athlete may have an effect on the amount of improvement made over a training period.</li>
</ul>
<h3>The Relationship Between Strength and Power:</h3>
<ul>
 <li>Relationship Between Strength and Power: <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;"> <span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">There is a moderate correlation between increased strength and increased RFD; however, further studies demonstrate stronger relationships when additional factors are considered.</li>
 <li>Sport Experience: Max strength is correlated with power; however, peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> is highest in more experienced athletes and athletes participating in <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> sports.</li>
 <li>RFD at Higher Loads: Increased strength is correlated with the ability to maintain RFD at higher loads.</li>
 <li>Dynamic, Closed-chain &amp; Relative Load: The correlation between strength and high velocity activity is higher when strength is measured relative to body weight, is dynamic, and is closed-chain.</li>
 <li>Movement Pattern Dependent: The relationship between strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> is weak when the strength measure does not sufficiently approximate the <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> movement pattern.</li>
 <li>Velocity Dependent: Higher velocity lifts (e.g. Olympic Lifts) are more strongly correlated with <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> than slower lifts.</li>
 <li>Change of Direction: Long-term adaptations to strength training in conjunction with sports training may improve change of direction speed; however, this relationship is likely limited to the degree of the change in direction, and it seems likely that there is a limit to the amount that strength can improve change of direction speed.</li>
</ul>

<h3>Strength Training for Power:</h3>
<ul>
 <li>Strength Training Improves Power: Significant improvement in <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, especially force production during the early phase of the concentric contraction, may be achieved with moderate load strength training; however, incorporating near maximal loads is likely ideal for <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> development.</li>
 <li>Strength Training Improves <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">Power</a> In Season: The addition of strength training to an in-season training program may enhance attributes that may be beneficial to sports performance, including acceleration, linear speed, strength, CMJ height, and peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">Power</a>. Note, the amount of improvement made from strength training is likely to decrease with experience.</li>
</ul>
<h3>Power Training for Power:</h3>
<ul>
 <li>Power Training Improves Power: <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">Power</a> training results in significant increases in RFD and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">Power</a> performance, and often improvements occur without concurrent increases in strength, hypertrophy, or changes in pennation angle. This likely implies that adaptations are primarily neuromuscular. Note, stronger athletes may benefit more from <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">Power</a> training than weaker athletes.</li>
 <li>Power Training Improves <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">Power</a> In-Season: The addition of ballistic training to an athletes program may significantly increase variables associated with peak power; and further, replacing some in-season max strength training with ballistic training may even reduce the decrease in <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">Power</a> performance noted over the course of in-season play.</li>
</ul>
<img title="An explosive (powerful) start from sprinters in a track meet" src="https://www.datocms-assets.com/25800/1649306258-sprinters-glutes-1.jpeg" alt="Sprinters explosively taking off out of the starting block">
<h3>Comparing Strength and Power Training for Power:</h3>
<ul>
 <li>Overlap: Both strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training may result in significant improvements in <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>.</li>
 <li>Power Training Better for Power: <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">Power</a> training is likely more beneficial than strength training for improving high-velocity tasks, especially for individuals with training experience.</li>
 <li>Power Training for Strength: <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">Power</a> training may have a larger impact on strength than strength training has on <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">Power</a>.</li>
</ul>
<h3>Combining Strength and Power Training:</h3>
<ul>
 <li>Combination vs. Strength or <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">Power</a> Alone: The combination of strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">Power</a> training is ideal for improving <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">Power</a> when compared to either strength or <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">Power</a> training alone.</li>
 <li>Additional Factors: Combination training is effective, when done simultaneously or in concurrent phases, and may be beneficial for maintaining type IIx fiber proportion; however, the <a id="specificity" data-tip="1223" target="_blank" href="/glossary-term/specificity" class="glossary">specificity</a> of the exercises selected should be considered, as well as the amount of high-velocity activity already included in sport or practice.</li>
</ul>

<h3>Intensity</h3>
<ul>
 <li>Specificity: Training that focuses on unloaded or lightly loaded repetitions that maximize speed is likely more beneficial for agility and maximal velocity tasks. Heavier repetitions may be more beneficial for improving loaded ballistic motions like Olympic lifting or potentially overcoming the inertia of linear acceleration.</li>
 <li>When to Load: External load can augment gains if the load does not reduce velocity enough to reduce peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, and/or the goal is to increase the ability to generate <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> with load.</li>
 <li>Novice vs. Trained: Bodyweight training is likely <a id="superior" data-tip="1570" target="_blank" href="/glossary-term/superior" class="glossary">superior</a> for improving <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> for novice individuals; however, trained individuals may benefit from additional intensity by either adding height to a depth jump or adding external load not to exceed 20-30% of 1RM.</li>
</ul>
<h3>Volume:</h3>
<ul>
 <li>Sufficient not Excessive: Volume is secondary to intensity, and while sufficient volume is necessary to ensure adaption, increasing volume (more than 3 - 5 sets) may not result in additional benefits.</li>
 <li>Maintenance: Training adaptations may be maintained with 1 session per week.</li>
</ul>
<h3>Repetitions:</h3>
<ul>
 <li>Rep Range: There is currently no research comparing rep ranges for high velocity activities, but based on the most commonly used rep ranges in <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training studies, 3-10 reps/set is likely a reasonable recommendation. A more <a id="specificity" data-tip="1224" target="_blank" href="/glossary-term/specificity" class="glossary">specific</a> recommendation would be to limit repetitions to the number of reps that can be performed at maximum velocity.</li>
</ul>
<h3>Additional Factors:</h3>
<ul>
 <li>Quick Intent: Research has demonstrated that repeated attempts with the intent to produce force quickly may be more important to developing force than the actual shortening and lengthening of the musculotendinous unit.</li>
 <li>Follow Through: Following all the way through (letting go, leaving the ground, etc.) is likely to result in greater EMG activity, better kinematics, and larger improvements from training.</li>
 <li>Soft Landing/Catching: Softer landing/catching reduces <a id="ground-reaction-force" data-tip="1397" target="_blank" href="/glossary-term/ground-reaction-force" class="glossary">ground reaction forces</a>, largely by increasing the amount of joint motion (excursion).</li>
 <li>Foot Placement: Although <a id="posture" data-tip="1660" target="_blank" href="/glossary-term/posture" class="glossary">form</a> is an important consideration for all exercise, it is unlikely that a special foot placement will result in additional benefit.</li>
</ul>

<h3>Choosing Phases:</h3>
<ul>
 <li>Strength Training: Moderate load strength training may be beneficial (especially in novice lifters); however, incorporating near maximal loads is likely ideal for <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> development.</li>
 <li>Power Training: Power training is likely more beneficial than strength training for improving high-velocity tasks, especially for individuals with training experience.</li>
 <li>Combined Training: The combination of strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training is likely more beneficial than either strength or <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training alone; however, the amount of high-velocity activity already included in sport and/or practice must be considered.</li>
</ul>
<h3>Acute Variables:</h3>
<ul>
 <li>Volume: 3 - 5 sets
 <ul>
 <li>Sufficient volume is necessary to ensure adaption; however, increasing volume beyond 3-5 high-quality sets per <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> group is unlikely to provide any additional benefit. Additional volume may actually result in a reduction in type IIx fiber proportion.
 <ul>
 <li>Training adaptations may be maintained with just 1 session per week.</li>
 </ul>
 </li>
 </ul>
 </li>
 <li>Repetitions (reps): 3 - 10 reps, or the number of reps that can be performed at max velocity.
 <ul>
 <li>There is currently no research comparing rep ranges of high-velocity activities, but based on the most commonly used rep ranges in <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training studies, 3-10 repetitions/set is likely a reasonable recommendation. A more <a id="specificity" data-tip="1224" target="_blank" href="/glossary-term/specificity" class="glossary">specific</a> recommendation would be to limit reps to the number that can be performed at max velocity.</li>
 </ul>
 </li>
</ul>
<h3>Loading:</h3>
<ul>
 <li>Max Velocity: As much load as can be moved with max velocity.
 <ul>
 <li>Intensity/load is likely best determined by the ability to achieve maximum velocity. Bodyweight training is likely <a id="superior" data-tip="1570" target="_blank" href="/glossary-term/superior" class="glossary">superior</a> for novice individuals; whereas, trained individuals may benefit from adding height to a depth jump (not to exceed 50-60cm), or adding external load (not to exceed 20-30% of 1RM).</li>
 </ul>
 </li>
 <li>Eccentric Load: Always include a quick eccentric contraction. Increasing eccentric demand is appropriate for progressing <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercise (e.g. higher depth jump).
 <ul>
 <li>Note, studies imply that improvements in concentric force production from an increase in eccentric load are limited to about 50cm depth jumps, and about 45% of 1-RM for upper body exercises in advanced athletes, and these limits would be much lower in novice individuals, recreational exercises, and athletes who have not reached peak levels of strength.</li>
 </ul>
 </li>
 <li>Amortization phase: NEVER purposefully allow weights to touch the floor, bounce off racks, or allow a pause during this phase of a <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercise (and, it is also not recommended during strength training for <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> athletes). A goal of <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training should be to shorten the <a id="amortization-phase" data-tip="1546" target="_blank" href="/glossary-term/amortization-phase" class="glossary">amortization phase</a> as much as possible.
 <ul>
 <li>Overcoming the <a id="amortization-phase" data-tip="1546" target="_blank" href="/glossary-term/amortization-phase" class="glossary">amortization phase</a> requires the synchronization of the maximal impulse of <a id="motor-unit" data-tip="1303" target="_blank" href="/glossary-term/motor-unit" class="glossary">motor unit</a> recruitment, neuromuscular coordination, and the synchronous shortening of the muscle/tendon complex. Allowing the floor or rack to impart force, or disrupt this complex sequence during training, is likely to reduce the transference of gains made from training to daily activity and sport.</li>
 </ul>
 </li>
 <li>Concentric Load: Ensure any <a id="exercise-progression" data-tip="1182" target="_blank" href="/glossary-term/exercise-progression" class="glossary">progressions</a> that involve an increase in load do so during the earliest part of the concentric contraction. Increasing load at the end of a contraction with apparatus like bands and chains is not likely to have a positive impact on the force/velocity curve of <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercise.</li>
 <li>Quick Intent: Research has demonstrated that repeated attempts with the intent to produce force quickly may be more important to developing force than the actual shortening and lengthening of the musculotendinous unit.</li>
 <li>Follow Through: Following all the way through (letting go, leaving the ground, etc.) is likely to result in greater EMG activity, better kinematics, and larger improvements from training.</li>
 <li>Soft Landing/Catching: Softer landing/catching reduces reaction forces, largely by increasing the amount of joint motion (excursion), which may reduce the wear and tear inherent in high-intensity training.</li>
</ul>
<h3>Progressions:</h3>
<ul>
 <li>Power <a id="exercise-progression" data-tip="1182" target="_blank" href="/glossary-term/exercise-progression" class="glossary">Progressions</a> based on Power = Force x Distance/Time:
 <ul>
 <li>Decrease Time: Decrease time to cover the same distance/height, or complete the same number of reps</li>
 <li>Increase Distance: Increase distance/height while maintaining speed and/or time</li>
 <li>Increase Force: Increase force by increasing load while maintaining speed and/or distance/height</li>
 </ul>
 </li>
 <li>Evidence-based Exercise Progressions:
 <ul>
 <li>Upper Body
 <ul>
 <li>4 - 12 cm Box Drop Push-Up</li>
 <li>Clap Push-Up</li>
 <li>Unstable Environments</li>
 </ul>
 </li>
 <li>Lower Body
 <ol>
 <li>Counter Movement Jump</li>
 <li>Box Jump</li>
 <li>Cone hop</li>
 <li>Single leg jump</li>
 <li>Depth jump</li>
 <li>Tuck jump</li>
 </ol>
 </li>
 </ul>
 </li>
</ul>
<img title=" Box jumps are another effective tool to improve &lt;a id=" power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power production&quot; src=&quot;https://www.datocms-assets.com/25800/1649512741-boxjump-1.jpeg&quot; alt=&quot;A box jump being demonstarted by a client&quot;&gt; Box Jumps are another effective tool to improve <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> production. Image courtesy of BrentBrookbush.com

Definitions (Foundational Concepts)

<h3>Power:</h3>
Before we explain &#x201C;power&#x201D; as it is used by human movement professionals, let&#x2019;s start with the definition of <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> as it is used by physicists. <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> is the rate at which &#x201C;work&#x201D; is done. &#x201C;Work&#x201D; is defined as (force x distance). <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> = &#x201C;How fast did you work?&#x201D;, or <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> = Force x Distance/Time. When human movement professionals use this term they are most often referring to the speed component of this equation (distance/time). That is, human movement professionals most often use the term <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> to refer to explosiveness, ballistic movement, jump height, and sprint speed. However, the distance and force components cannot be forgotten, because, like speed, both distance and force can be modified to progress <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercise.
<table>
 <tbody>
 <tr>
 <td>Practical Application: Power Exercise Progressions based on Power = Force x Distance/Time:
 <ul>
 <li>Decrease time to cover the same distance/height, or complete the same number of reps</li>
 <li>Increase distance/height while maintaining speed and/or time</li>
 <li>Increase force by increasing load while maintaining speed and/or distance/height</li>
 </ul>
 </td>
 </tr>
 </tbody>
</table>
<a href="https://brookbush.s3.us-east-2.amazonaws.com/wordpress/wp-content/uploads/2017/09/Power.gif" target="_blank" rel="noopener"><img src="https://brookbush.s3.us-east-2.amazonaws.com/wordpress/wp-content/uploads/2017/09/Power.gif" alt="Power = force x velocity (equation)" title="The equation breakdown for power"></a>
<h3>Torque:</h3>
<a id="torque" data-tip="1294" target="_blank" href="/glossary-term/torque" class="glossary">Torque</a> refers to a force applied to a lever that moves in a circle (arc) around an axis. In the human body, most muscles produce <a id="torque" data-tip="1294" target="_blank" href="/glossary-term/torque" class="glossary">Torque</a>, because most bones move around the fixed axis of a joint. <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">Power</a> relative to a single joint is often expressed as the product of joint <a id="torque" data-tip="1294" target="_blank" href="/glossary-term/torque" class="glossary">Torque</a> and angular velocity (speed around an axis). These terms are similar to the terms force, distance, and speed described above.
<ul>
 <li><a id="torque" data-tip="1294" target="_blank" href="/glossary-term/torque" class="glossary">Torque</a> = Force</li>
 <li>Angular Velocity = Speed in a circle</li>
 <li>Distance = Arc or Degrees around a circle</li>
</ul>
When force pulls in a straight line, on a lever (of a fixed length) that moves around a fixed axis, the moment arm (mechanical advantage) will continue to change. For example, if you attach a string with a weight on the end, to the hour hand of a clock, the amount of <a id="torque" data-tip="1294" target="_blank" href="/glossary-term/torque" class="glossary">torque</a> produced would be different depending on the time. The string and weight could generate the most <a id="torque" data-tip="1294" target="_blank" href="/glossary-term/torque" class="glossary">torque</a> when the hour hand was at 3 o&#x2019;clock or 9 o&#x2019;clock, and the least amount of force at 6 o&#x2019;clock or 12 o&#x2019;clock. In the human body, muscles pull in straight lines and bones move in a circular fashion around joints, so the <a id="torque" data-tip="1294" target="_blank" href="/glossary-term/torque" class="glossary">torque</a> generated by the <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> changes throughout the range of motion (ROM).
<ul>
 <li>Single Joint vs. Multi-Joint: Research on <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> uses both single-joint angular velocity (e.g knee extension degrees/second) and measures of multi-joint or total body <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> (e.g. box jumps). Due to various body shapes, sizes, skill levels, and experience of the participants in a study, single joint <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> cannot be accurately determined from the performance of multi-joint movements.</li>
</ul>
<img src="https://www.datocms-assets.com/25800/1649705308-biceps-muscle.jpg" title="Illustration of elbow flexors. Note: The elbow flexors each pull in a linear fashion, but the elbow forces the joint to move in an arc." alt="The elbow flexors in a single-joint motion of a biceps curl"> By OpenStax College - http://cnx.org/content/m46487/latest/?collection=col11496/latest, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=29631545 Illustration of elbow flexors. Note: The elbow flexors each pull in a linear fashion, but the elbow forces the joint to move in an arc.

The force-velocity curve expresses the relationship between the amount of force a <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> can generate and the speed at which a joint is moving. The relationship is influenced by factors related to the speed of cross-bridging between <a href="https://brookbushinstitute.com/courses/muscle-cell-structure-function" target="_blank" rel="noopener">myosin and actin filaments</a>, the speed of protein conformation change (especially of myosin <a id="isoform" data-tip="1276" target="_blank" href="/glossary-term/isoform" class="glossary">isoforms</a>), <a id="connective-tissue-cell" data-tip="1368" target="_blank" href="/glossary-term/connective-tissue-cell" class="glossary">connective tissue</a> <a id="tension" data-tip="1229" target="_blank" href="/glossary-term/tension" class="glossary">tension</a>, <a id="rate-coding" data-tip="1293" target="_blank" href="/glossary-term/rate-coding" class="glossary">rate coding</a>, speed of <a id="motor-unit" data-tip="1303" target="_blank" href="/glossary-term/motor-unit" class="glossary">motor unit</a> recruitment, and <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> cross-sectional area (CSA). As speed increases beyond a certain threshold, the cross-bridge to force ratio decreases (cross-bridging cannot keep pace). This decrease in relative cross-bridging is far more pronounced during explosive concentric contractions than it is during explosive eccentric contractions. Eccentric contractions likely benefit far more from the passive <a id="tension" data-tip="1229" target="_blank" href="/glossary-term/tension" class="glossary">tension</a> created by lengthening <a id="connective-tissue-cell" data-tip="1368" target="_blank" href="/glossary-term/connective-tissue-cell" class="glossary">connective tissue</a> (fascia). For example, Demura et al. demonstrated that the <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> generated during an eccentric load of 130% of maximum voluntary contraction (MVC) was moderately correlated with the <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> generated during a concentric load of 60% MVC (1). That is analogous to saying that a 60% concentric MVC takes about the same effort as 130% eccentric MVC. Understanding the relationship between <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> contraction and velocity has many implications for performance training.
<img title="The contraction and relaxation process of a muscle, with myofilaments in the sarcomere labeled" src="https://www.datocms-assets.com/25800/1649646390-sarcomere.png" alt="A sarcomere, the smallest contractile unit of a muscle, with actin and myosin labeled">
Two conditions, at opposite ends of the force/velocity curve, prevent a <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> from producing any <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>. On the left side of the curve, a maximal isometric contraction produces no motion despite significant cross-bridging (<a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> is dependent on &quot;work&quot; done, which is the product of force x distance). Picture trying to flip a truck with all of your might, resulting in a huge number of motor units recruited, but no motion. Although effort is significant, &quot;power&quot; is zero. To the right of the curve, the amount of momentum and velocity exceeds the rate at which cross-bridging/motor unit recruitment can contribute to force (<a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> is dependent on force). Picture running as fast as you can downhill until your legs outpace your ability to control them. <a id="optimal" data-tip="1571" target="_blank" href="/glossary-term/optimal" class="glossary">Optimal</a> <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> is produced between these two extremes, with the human body being a bit more efficient at recruiting more motor units at slower speeds. These conditions result in the upside-down U-shape curve with a slight bias to the left, as depicted below.
Adaptations to training may alter the force/velocity curve, discussed in detail below. Theoretically, improving one-repetition maximum strength (1RM) by training with relatively slow controlled movements (for example, heavy bench press) would shift the curve up and to the left, resulting in greater peak force (not the same as peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>) but slower velocity. Conversely, sprint training requiring sub-maximal forces with maximal rate of force development (RFD) and peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> would shift the curve up and to the right. Several studies have investigated the difference between athletes and novices, the shape of the force-velocity curve, and how the shape of the curve may be influenced by training. For example, Cormie et al. demonstrated a significant difference between experienced and inexperienced exercises in both strength and the shape of force/velocity curve throughout a counter-movement jump (athletes exhibited a shift up and to the right). Further, 12 weeks of <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training affected both strength, as well as the shape of the force/velocity curve (up and right shift) of a counter-movement jump in both previously trained and untrained participants (2). Changes in the force/velocity curve is a measure used in various research studies covered in this course. Generally, an increase in peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> will result in a shift up and to the right of the force/velocity curve, representing a significant increase in the rate of force development (RFD). Note, do not confuse &quot;velocity&quot; with &quot;time&quot; in the graph below. If this were a force/time curve for <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, then an increase in <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> would result in a left shift in the graph.
<img src="https://www.datocms-assets.com/25800/1649705428-force-velocity-curve.png" title="Examples of exercies in the force velocity curve" alt="The force velocity curve">
Force Velocity Curve

Neural Adaptations

<h3>Rate Coding:</h3>
Several studies have demonstrated that an increase in <a id="rate-coding" data-tip="1293" target="_blank" href="/glossary-term/rate-coding" class="glossary">rate coding</a> (frequency) plays a role in achieving the force required for high velocity contractions; and further, that improvements in <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> performance following training are due at least in part to an increase in the frequency of action potentials (<a id="rate-coding" data-tip="1293" target="_blank" href="/glossary-term/rate-coding" class="glossary">rate coding</a>).
<ul>
 <li>Rate Coding (a.k.a. frequency coding) - As the intensity of a stimulus increases, the rate/frequency of action potentials increases. <a id="rate-coding" data-tip="1293" target="_blank" href="/glossary-term/rate-coding" class="glossary">Rate Coding</a> is a <a id="model" data-tip="1469" target="_blank" href="/glossary-term/model" class="glossary">model</a> of <a id="nerve-cell" data-tip="1361" target="_blank" href="/glossary-term/nerve-cell" class="glossary">nerve</a> communication in which additional information is conveyed by the frequency of action potentials, with the assumption that the shape and amplitude of an <a id="action-potential-2" data-tip="1240" target="_blank" href="/glossary-term/action-potential-2" class="glossary">action potential</a> are relatively fixed. Research suggests that <a id="rate-coding" data-tip="1293" target="_blank" href="/glossary-term/rate-coding" class="glossary">Rate Coding</a> is influenced by contraction type, training experience, and age.
 <ul>
 <li>Doublet firing pattern - Quick discharge of two concurrent action potentials.</li>
 </ul>
 </li>
</ul>
Several studies demonstrate that reliance on <a id="rate-coding" data-tip="1293" target="_blank" href="/glossary-term/rate-coding" class="glossary">rate coding</a> to increase force varies between <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> groups. De Luca et al. demonstrated that when force increased from 40% - 80% of maximum voluntary isometric contraction (MVIC), the <a href="https://brookbushinstitute.com/courses/deltoids" target="_blank" rel="noopener">deltoid</a> muscles met that demand primarily with an increase in <a id="motor-unit" data-tip="1303" target="_blank" href="/glossary-term/motor-unit" class="glossary">motor unit</a> recruitment, whereas the first <a id="dorsal" data-tip="1554" target="_blank" href="/glossary-term/dorsal" class="glossary">dorsal</a> interosseous (FDI) <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> met the demand primarily with an increase in <a id="rate-coding" data-tip="1293" target="_blank" href="/glossary-term/rate-coding" class="glossary">rate coding</a>. These findings were similar for normal subjects and highly trained performers (long&#x2010;distance swimmers, powerlifters, and pianists) (3). Similarly, Kukulka et al. demonstrated that the biceps brachii accommodated increases in load from 0 to 88% MVIC primarily with an increase in <a id="motor-unit" data-tip="1303" target="_blank" href="/glossary-term/motor-unit" class="glossary">motor unit</a> recruitment, while the adductor pollicis accommodated increases in load greater than 30% primarily with changes in <a id="rate-coding" data-tip="1293" target="_blank" href="/glossary-term/rate-coding" class="glossary">rate coding</a> (4). Desmedt et al. demonstrated a similar trend, noting that the larger <a href="https://brookbushinstitute.com/courses/soleus" target="_blank" rel="noopener">soleus</a> relied more on <a id="motor-unit" data-tip="1303" target="_blank" href="/glossary-term/motor-unit" class="glossary">motor unit</a> recruitment than the masseter or first <a id="dorsal" data-tip="1554" target="_blank" href="/glossary-term/dorsal" class="glossary">dorsal</a> interosseous <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> (5). These studies suggest a trend that larger muscles tend to rely more on <a id="motor-unit" data-tip="1303" target="_blank" href="/glossary-term/motor-unit" class="glossary">motor unit</a> recruitment to increase force production, while smaller muscles primarily rely on <a id="rate-coding" data-tip="1293" target="_blank" href="/glossary-term/rate-coding" class="glossary">rate coding</a>. This trend seems to persist at higher contraction velocities; however, both <a id="motor-unit" data-tip="1303" target="_blank" href="/glossary-term/motor-unit" class="glossary">motor unit</a> recruitment and <a id="rate-coding" data-tip="1293" target="_blank" href="/glossary-term/rate-coding" class="glossary">rate coding</a> increase with increases in RFD for small and large muscles.
<a id="rate-coding" data-tip="1293" target="_blank" href="/glossary-term/rate-coding" class="glossary">Rate coding</a> has a significant influence on the rate of force development (RFD). In a study mentioned above by Desmedt et al., both slow and fast contractions resulted in a similar recruitment order (small to large) of motor units, at least from those motor units measured by the same electrode for each <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> tested (masseter, <a href="https://brookbushinstitute.com/courses/soleus" target="_blank" rel="noopener">soleus</a>, and first <a id="dorsal" data-tip="1554" target="_blank" href="/glossary-term/dorsal" class="glossary">dorsal</a> interosseous) (5). However, Desmedt et al. also demonstrated that the recruitment strategies of the <a href="https://brookbushinstitute.com/courses/tibialis-anterior" target="_blank" rel="noopener">tibialis anterior</a> differed when slow ramp contractions were compared to ballistic contractions. Slow ramp contractions resulted in a consistent, near-linear increase in discharge frequency and consistent recruitment order of motor units, whereas fast contractions resulted in transient bursts of increased frequency, and somewhat less organized <a id="motor-unit" data-tip="1303" target="_blank" href="/glossary-term/motor-unit" class="glossary">motor unit</a> recruitment patterns (6). These studies may suggest that within a <a id="motor-unit" data-tip="1303" target="_blank" href="/glossary-term/motor-unit" class="glossary">motor unit</a> or cluster of motor units, recruitment strategies remain consistent; however, high velocity contractions result in large bursts of activity and increases in <a id="rate-coding" data-tip="1293" target="_blank" href="/glossary-term/rate-coding" class="glossary">Rate coding</a> that may alter the order in which clusters of motor units are recruited, likely in an attempt to access more or larger motor units, faster.
<img src="https://www.datocms-assets.com/25800/1647306501-1642021906-nerves-in-body.png" title="The nerves in the body, labeled with their locations outlined" alt="The central and peripheral nervous system">
Doublet discharge rates likely play a role in the increase in <a id="rate-coding" data-tip="1293" target="_blank" href="/glossary-term/rate-coding" class="glossary">rate coding</a> and RFD exhibited during ballistic contractions. Bawa et al. demonstrated that both slow and fast motor units resulted in doublet discharges; however, initial doublet discharges decreased as contraction speed increased. Interestingly, this study reported that the flexor carpi radialis demonstrated a tendency toward relying on doublet discharges during an initial slow ramp up, and then adopted a more normal firing pattern (increase in <a id="motor-unit" data-tip="1303" target="_blank" href="/glossary-term/motor-unit" class="glossary">motor unit</a> recruitment) as the force increased; however, the motor units discharging doublets at slower speeds had higher maximal firing rates at higher speeds (7). Christie et al. demonstrated that doublet discharges were correlated with higher force production from single motor units, and further that there were fewer doublet discharges recorded in older individuals (8). Klass et al. also demonstrated that older adults had slower <a id="motor-unit" data-tip="1303" target="_blank" href="/glossary-term/motor-unit" class="glossary">motor unit</a> discharge rates (-27%), including about half the amount of doublet discharges (4.6 vs. 8.4% of the total number of action potentials), which correlated with significantly slower RFD (-48%) when compared to younger adults (9). These studies suggest that doublet discharge rates may play a role in initial force development, are correlated with higher frequency motor units, and an increase in motor units firing doublet discharges is correlated with an increase in RFD, especially early in contraction. Conversely, slower discharge rates are correlated with a reduction in doublet discharge and are correlated with the decrease in RFD exhibited by older adults.

Several studies have demonstrated that the increase in RFD from resistance or <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training is correlated with an increase in EMG activity. Van Cutsem et al. demonstrated that 12 weeks of dynamic resistance training resulted in an increase in maximal strength and RFD (average 82%), and the increase was attributable in part to earlier increases in <a id="motor-unit" data-tip="1303" target="_blank" href="/glossary-term/motor-unit" class="glossary">motor unit</a> activation, enhanced maximal firing rates, and an increase from 5.2 to 32.7 % (average) of motor units discharging doublets (10). Hakkinen et al. (1985) demonstrated that body weight and lightly resisted jumping exercises performed 3x&apos;s/week for 24 weeks resulted in large increases in fast force production, with relatively small increases in maximal strength. These changes were largely correlated with an increase in the average EMG time curve (more activity faster), as well as an increase in type II fiber proportion, and a relatively small amount of hypertrophy (11). Hakkinen et al. (1990) demonstrated that during 16-weeks of <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training, the largest improvements were made during earlier weeks. These improvements occurred due to increased RFD in the early portion of the force-time curve as a result of increased neural activation (EMG) of the trained muscles (12). Aagard et al. demonstrated that following 14 wk of heavy-resistance strength training (38 sessions), 15 male subjects exhibited significant increases in MVIC and RFD, attributable to increases in <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> EMG by 22&#x2013;143% (mean average voltage), and increases in the rate of EMG rise early in the contraction phase (force-velocity curve) (0&#x2013;200 ms) of 41&#x2013;106% (13). In a study by Tillin et al., <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> athletes performing explosive knee extensions were 28% stronger, and in the first 50 milliseconds had twice the absolute RFD, greater normalized RFD, and greater neural activation than controls (14). Folland et al. demonstrated significant variability in EMG and RFD in untrained individuals and a decrease in variability with training in favor of an earlier and more significant increase in EMG activity (15). In summary, increases in <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> following training are strongly correlated with an increase in RFD, resulting from a significant increase in EMG activity, especially during the earliest part of a concentric contraction (force-velocity curve).
<table>
 <tbody>
 <tr>
 <td>Practical Application: Increase Early EMG to Improve RFD
 <ul>
 <li>If the goal is increased <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, increases in load/intensity should occur during the earliest portion of the concentric contraction (or throughout the contraction), not the end of a contraction as would be the case when adding bands or chains to external loads.</li>
 <li>Do not allow weights to touch down between reps. Repetitions should include overcoming the <a id="amortization-phase" data-tip="1546" target="_blank" href="/glossary-term/amortization-phase" class="glossary">amortization phase</a> (transition between eccentric to concentric contraction), which is the true beginning of concentric force production.</li>
 <li>Consider increasing intensity by increasing eccentric load. This would result in an increase in the challenge associated with overcoming the <a id="amortization-phase" data-tip="1546" target="_blank" href="/glossary-term/amortization-phase" class="glossary">amortization phase</a> and the earliest part of the concentric contraction (For more on this recommendation see the section &quot;Pre-stretch&quot;).</li>
 </ul>
 </td>
 </tr>
 </tbody>
</table>
<h4>Motor Unit Recruitment Threshold and Ca2+ Sensitivity</h4>
A decrease in <a id="motor-unit" data-tip="1303" target="_blank" href="/glossary-term/motor-unit" class="glossary">motor unit</a> recruitment threshold following <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training may be a contributing factor to the increase in EMG activity noted during the early portion of the concentric phase of high velocity contractions, and the resulting increase in RFD. Z&apos;Graggen et al. demonstrated that 2 weeks of resistance training resulted in a decrease in the relative <a id="refractory-period" data-tip="1235" target="_blank" href="/glossary-term/refractory-period" class="glossary">refractory period</a>, which would allow for an increase in the frequency of action potentials (<a id="rate-coding" data-tip="1293" target="_blank" href="/glossary-term/rate-coding" class="glossary">rate coding</a>). The researchers hypothesized that this adaptation was due to hyperpolarization of the resting <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> membrane potential, resulting from an increase in the number of sodium pump sites (16). Ortenblad et al. evaluated sarcoplasmic reticulum (SR) function from resting vastus lateralis <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> biopsies, before and after 5 weeks of a sprint training program (10 sets of 8 seconds max effort, with 32-second intermittent rest intervals). Performance was enhanced an average of 12% after training, and biopsy demonstrated enhanced peak SR Ca2+ <a id="release" data-tip="1249" target="_blank" href="/glossary-term/release" class="glossary">release</a>, due to an enhanced SR total volume (17). (Note, Ca2+ is short-hand for &quot;calcium ions&quot; which play a role in initiating contraction). Li et al. demonstrated that SR Ca2+ <a id="release" data-tip="1249" target="_blank" href="/glossary-term/release" class="glossary">release</a>, Ca2+ uptake, and Ca2+-ATPase activity were correlated with type II fiber proportion, and resting levels were higher in resistance-trained individuals when compared to endurance-trained individuals or controls (18). Widrick et al. demonstrated that the increase in <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> following 12 weeks of progressive resistant training was correlated with an increase in CSA and peak Ca2+ activated force of all fiber types (19). Last, Lynch et al. demonstrated that sprint training increased type IIx fiber proportion and further that IIx fibers experienced larger alterations in Ca2+ <a id="sensitivity" data-tip="1226" target="_blank" href="/glossary-term/sensitivity" class="glossary">sensitivity</a> than other fiber types (20). These studies demonstrate that the increase in <a id="motor-unit" data-tip="1303" target="_blank" href="/glossary-term/motor-unit" class="glossary">motor unit</a> recruitment associated with <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training is due in part to an increase in Ca2+ <a id="sensitivity" data-tip="1226" target="_blank" href="/glossary-term/sensitivity" class="glossary">sensitivity</a>. This increased <a id="sensitivity" data-tip="1226" target="_blank" href="/glossary-term/sensitivity" class="glossary">sensitivity</a> is likely due to an increase in the proportion of type II fibers which are more <a id="sensitivity" data-tip="1227" target="_blank" href="/glossary-term/sensitivity" class="glossary">sensitive</a> to Ca2+ than type I fibers, as well as increases in membrane potential, SR total volume, SR Ca2+ <a id="release" data-tip="1249" target="_blank" href="/glossary-term/release" class="glossary">release</a>, Ca2+ uptake, Ca2+-ATPase activity, and peak Ca2+ activated force.
<img src="https://www.datocms-assets.com/25800/1647307095-1642021965-motor-unit.jpeg" title="An image of a muscle, the fibers of the muscle, and the innervation of the motor unit" alt="A picture of the motor unit and the muscle tissue">

Studies have highlighted a complex relationship between co-activation and RFD. Carpentier et al. demonstrated that as the velocity of voluntary plantarflexion increased, so did <a href="https://brookbushinstitute.com/courses/tibialis-anterior" target="_blank" rel="noopener">tibialis anterior</a> (<a id="antagonists" data-tip="1705" target="_blank" href="/glossary-term/antagonists" class="glossary">antagonist</a>) activity (21). Arai et al. demonstrated that an increase in box height and/or rebound height during depth jumps resulted in an increase in both agonist and <a id="antagonists" data-tip="1705" target="_blank" href="/glossary-term/antagonists" class="glossary">antagonist</a> activity (<a id="medial" data-tip="1568" target="_blank" href="/glossary-term/medial" class="glossary">medial</a> gastrocnemius, <a href="https://brookbushinstitute.com/courses/soleus" target="_blank" rel="noopener">soleus</a>, and <a href="https://brookbushinstitute.com/courses/tibialis-anterior" target="_blank" rel="noopener">tibialis anterior</a>) immediately before and after impact (22). A study by Gollhofer et al. demonstrated that co-activation of antagonists (quadriceps and <a href="https://brookbushinstitute.com/courses/biceps-femoris" target="_blank" rel="noopener">hamstrings</a>) was greatest during a CMJ when compared to the lower velocity loaded jump squats or depth jumps (23). These studies suggest that co-activation increases with the velocity of motion; however, further studies suggest a more complex relationship.
Several studies have demonstrated that co-activation of antagonists is not a simple linear relationship. Mokhtarzadeh et al. demonstrated co-activation of the quadriceps and <a href="https://brookbushinstitute.com/courses/biceps-femoris" target="_blank" rel="noopener">hamstrings</a> during a double-leg landing from a 30cm height; however, when landing from a 60cm height only activity of the quadriceps increased further (24). Bazzucchi et al. demonstrated that tennis players when compared to controls, exhibited lower levels of <a id="antagonists" data-tip="1705" target="_blank" href="/glossary-term/antagonists" class="glossary">antagonist</a> activity during MVIC of elbow flexors (25). Matsuda et al. compared co-activation of the <a href="https://brookbushinstitute.com/courses/biceps-femoris" target="_blank" rel="noopener">biceps femoris</a> and rectus femoris in competitive and recreational swimmers while flutter kicking, demonstrating that activity of the rectus femoris was lower during hip extension in competitive swimmers (26). Hakkinen et al. investigated adaptations following 6 months of combined maximal strength and explosive exercise, demonstrating that isometric strength, squat jump, and cross-sectional area, as well as better <a id="integration" data-tip="1472" target="_blank" href="/glossary-term/integration" class="glossary">integration</a> of vastus medialis and vastus lateralis EMG, increased total quadriceps EMG overall, and decreased <a href="https://brookbushinstitute.com/courses/biceps-femoris" target="_blank" rel="noopener">biceps femoris</a> activity during leg extensions. Based on the relatively small changes in CSA, changes in performance are likely due to the alterations in EMG activity (27, 28). These studies imply that although co-activation increases with RFD, <a id="antagonists" data-tip="1705" target="_blank" href="/glossary-term/antagonists" class="glossary">antagonist</a> activity may have an upper limit; and further, training and experience may be correlated with a decrease in co-activation to allow for greater concentric force production.
Two studies demonstrate that performance increases resulting from <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training may be due at least in part to a reduction in <a id="antagonists" data-tip="1705" target="_blank" href="/glossary-term/antagonists" class="glossary">antagonist</a> activity. Hakkinnen et al. demonstrated that 6 months of training designed to increase strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> in middle-aged and older men and women resulted in some hypertrophy; however, increased agonist EMG and decreased <a id="antagonists" data-tip="1705" target="_blank" href="/glossary-term/antagonists" class="glossary">antagonist</a> EMG accounted for much of the improvement in the first two months (29). Geertsen et al. demonstrated that explosive strength training of the ankle dorsiflexors, 3x&apos;s/week for 4 weeks increased disynaptic <a id="reciprocal-inhibition" data-tip="1655" target="_blank" href="/glossary-term/reciprocal-inhibition" class="glossary">reciprocal inhibition</a> (as measured by depression of <a href="https://brookbushinstitute.com/courses/soleus" target="_blank" rel="noopener">soleus</a> H-reflex) from 6% before the training to 22% (30). These studies demonstrate that a decrease in co-activation may result from training, suggesting that the differences between recreational and competitive athletes are likely due, at least in part, to a training effect.
Although more research is needed, two studies have implied that the adaptations resulting in a reduction in <a id="antagonists" data-tip="1705" target="_blank" href="/glossary-term/antagonists" class="glossary">antagonist</a> activity are the result of complex <a id="nervous-system" data-tip="1690" target="_blank" href="/glossary-term/nervous-system" class="glossary">nervous system</a> interactions. A study by Manning et al. demonstrated that shortening of <a id="antagonists" data-tip="1705" target="_blank" href="/glossary-term/antagonists" class="glossary">antagonist</a> fibers (and <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> spindles) was not directly correlated with a reduction in <a id="antagonists" data-tip="1705" target="_blank" href="/glossary-term/antagonists" class="glossary">antagonist</a> activity, suggesting that <a id="antagonists" data-tip="1705" target="_blank" href="/glossary-term/antagonists" class="glossary">antagonist</a> activity must be influenced by more than <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> spindle activity (31). Dal Maso et al. compared strength-trained and endurance-trained individuals, demonstrating that strength-trained athletes exhibited lower <a id="antagonists" data-tip="1705" target="_blank" href="/glossary-term/antagonists" class="glossary">antagonist</a> activity in conjunction with lower corticomuscular coherence magnitude, providing direct evidence of the role of central mediation of <a id="antagonists" data-tip="1705" target="_blank" href="/glossary-term/antagonists" class="glossary">antagonist</a> activity (32). These studies demonstrate that <a id="antagonists" data-tip="1705" target="_blank" href="/glossary-term/antagonists" class="glossary">antagonist</a> inhibition is likely regulated by both peripheral and CNS mechanisms.
In summary, <a id="antagonists" data-tip="1705" target="_blank" href="/glossary-term/antagonists" class="glossary">antagonist</a> co-contraction increases with RFD; however, training and experience may decrease <a id="antagonists" data-tip="1705" target="_blank" href="/glossary-term/antagonists" class="glossary">antagonist</a> co-contraction via peripheral and CNS mechanisms to improve concentric force production and performance.

<ul>
 <li>Stretch Shortening Cycle (SSC) - A successive combination of eccentric and concentric action, resulting in more <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> generated during the concentric action than would be generated if the concentric action was performed alone. Research suggests high-velocity SSC contractions start with a forceful eccentric lengthening of <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> fibers while EMG activity increases, followed by a period of near isometric contraction of the activated <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> fibers while the tendon continues to lengthen, followed by shortening of both the tendon and the <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> complex during the concentric contraction.</li>
 <li>Counter-movement Jump (CMJ) - A jump that starts with a counter-movement; that is, a forceful quick descent and backswing of the arms (eccentric phase), followed by the shortest possible time in the bottom position (<a id="amortization-phase" data-tip="1546" target="_blank" href="/glossary-term/amortization-phase" class="glossary">amortization phase</a>), followed immediately by a forceful upward jump (concentric phase). This is the jumping motion most commonly associated with a vertical jump <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>.</li>
</ul>
<h4>Sequence of SSC Contractions</h4>
Several studies have investigated EMG activity, <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> length change, and tendon length change during high-velocity SSC contractions. Kawakami et al. demonstrated that, unlike concentric only contractions, SSC contractions with pre-stretch resulted in an initial lengthening of <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> fibers as EMG activity increased, followed by a near isometric contraction of <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> fibers while the musculotendinous unit continued to lengthen, followed by a shortening of the entire musculotendinous complex including the <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> fibers (33). Kurokawa et al. demonstrated a near isometric contraction of <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> fibers during pre-stretch, and a lengthening followed by a rapid shortening of the musculotendinous complex prior to further shortening of the <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> fibers during a vertical jump (34). Kubo et al. (2000) compared fast and slow, dorsiflexion and plantarflexion contractions, demonstrating that the fascicle length was shorter during the transition phase of faster contractions, implying more lengthening of the tendon structure during faster contractions, and quicker changes in the length of muscles and tendons. The observed relation between fascicle length and force suggested that tendon structures contributed between 20.2 and 42.5% of the force generated (35). These studies demonstrate that the increase in concentric force from SSC contractions is likely due to neuromuscular reflex initiated by a significant preload that increases concentric EMG activity, as well as a contribution from the elastic potential of lengthened myofascial tissue.
<h4>Tendon Stiffness:</h4>
Additional research has considered the role of tendon stiffness in force production during SSC contractions. Kubo et al. (2000) demonstrated that the vastus lateralis and gastrocnemius of sprinters exhibited greater <a id="elasticity-2" data-tip="1307" target="_blank" href="/glossary-term/elasticity-2" class="glossary">elasticity</a> during low loads when compared to controls, but tissue compliance was similar at higher loads. Further, it was demonstrated that greater <a id="elasticity-2" data-tip="1307" target="_blank" href="/glossary-term/elasticity-2" class="glossary">elasticity</a> at higher loads among sprinters was negatively associated with sprint performance (36). Secomb et al. compared various attributes of <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> structure to strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> performance in 14 surf athletes. Findings demonstrated that vastus lateralis thickness and an increase in <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> gastrocnemius pennation angle were correlated with improved performance in the CMJ, squat jump, and isometric mid-thigh pull. Further lower-body musculotendinous stiffness explained a large amount of the variance between an athlete&apos;s ability to generate force rapidly (37). Kubo et al. (2007) compared tendon stiffness following 12 weeks of resistance training of the plantar flexors of one ankle, to 12 weeks of <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> training of the plantar flexors of the other ankle of 10 participants. Tendon stiffness increased significantly following resistance training but not <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> training; however, joint stiffness increased significantly following <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> training and not weight training. There were no significant differences between groups for EMG activity; however, only <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> training significantly improved jump heights (38). Bojsen et al. using ultrasonography demonstrated that stiffness of the vastus lateralis tendon-aponeurosis complex was positively correlated with RFD and performance of jump squats and CMJ, with study findings indicating that tendon mechanical properties may account for up to 30% of the variance in RFD between trained men (39). Interestingly, Westh et al. compared experienced runners to untrained women and demonstrated that there was no significant difference in CSA, stress, or strain modules for the patellar or Achilles tendons (40). This likely implies that endurance running does not result in tendon adaptations that would increase <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> performance. <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> athletes may exhibit more <a id="elasticity-2" data-tip="1307" target="_blank" href="/glossary-term/elasticity-2" class="glossary">elasticity</a> at low loads, but increased tendon stiffness at higher loads is positively correlated with RFD and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> performance. Note, studies to date have not demonstrated that <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training results in acute changes in tendon stiffness. stiffness.
<h4>Pre-stretch</h4>
Pre-stretch, or a quick loading of the eccentric phase of a contraction, has a significant effect on concentric force production. Fukashiro et al. compared ankle-only static jumps to ankle-only depth jumps, demonstrating that the difference in <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> and musculotendinous length change was greater during the depth jump, which resulted in a large increase in elastic energy use and a larger vertical jump (41). Bobbert et al. demonstrated that even when squat jumps started at the same angle as the bottom position of a CMJ, jump height was still significantly higher during the CMJ (average of 3.4 cm in 6 male volleyball players) (42). Bosco et al. demonstrated that the peak force of jump squats from a static position with various loads (10 - 160 kg) was less than the peak force generated by jumps with a pre-stretch, including CMJ and depth jumps of various heights (20 to 100 cm) (43). Sheppard et al. compared various measures of strength, jumping ability, and anthropometrics, demonstrating that relative depth jump performance had the highest correlation with vertical jump height (44). Komi et al. compared jump heights during static squat jumps, counter-movement jump (CMJ) and various height depth jumps from 20-100 cm, demonstrating that jump height increased with pre-stretch load from squat jump to approximately 60 cm depth jumps in men, and 50 cm depth jumps in women (45). In a similar study, Asmussen et al. found that jump heights increased as pre-jump force increased from static quarter squats to jump squats to CMJ to depth jumps up to approximately 40 cm (46). Newton et al. demonstrated that average and peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> output was significantly higher for SSC throws (included pre-stretch) when compared to concentric only throw at all loads, with <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> output highest at 30 to 45% of 1-RM loads (47). These studies imply that improvements in concentric force production from eccentric load may be limited to about 50cm depth jumps and 30% of 1-RM for the upper body in advanced athletes, and the limits would be much lower in novice individuals, recreational exercisers, and athletes who have not reached peak levels of strength.
Several additional factors may play a role in optimizing concentric force output following pre-stretch. Similar to previously mentioned studies, Bosco et al. (1982) demonstrated that pre-stretch load increased jump height; however, this study also demonstrated that CMJ and loaded squat jumps resulted in similar <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> activity, and only depth jumps resulted in a significant increase in EMG activity (48). Bosco et al. (1987) also demonstrated that the efficiency difference between CMJ and static jumps exceeded the elastic potential of the leg extensor muscles, implying that other mechanisms must contribute to the increase in performance from pre-stretch loads (neuromuscular factors) (49). A study by Trimble et al. further supports the notion that neuromuscular reflex contributes to force production. Trimble et al. demonstrated that <a href="https://brookbushinstitute.com/courses/soleus" target="_blank" rel="noopener">soleus</a> and <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> gastrocnemius activity was larger during a reciprocal hop when compared to a concentric hop or MVIC. Further, electric stimulation alone could not replicate the EMG activity noted during the reciprocal hopping; however, adding a high-frequency EMG burst to an MVIC could be used to evoke similar activity (50). Voigt et al. demonstrated that lengthening of the calf complex during hoping resulted in short latency <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> spindle reflex activity; however, estimated peak <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> spindle stretch velocity was negatively correlated EMG amplitude and H-reflex did not change in parallel with the stretch reflex (51). This implies that stretch reflex alone cannot be the only factor contributing to the increase in concentric force output during an SSC. A study by Walshe et al. may demonstrate the contribution of both elastic potential and EMG to work output. Walshe et al. compared the work output and EMG of concentric only squats, concentric squats with an isometric pre-load, and CMJ, demonstrating that isometric load and CMJ squats resulted in similar EMG activity that was greater than concentric only squats, and further, that CMJ resulted in the largest work output than squats with an isometric pre-load (52). These studies demonstrate that the increase in concentric force from SSC contractions is likely due to neuromuscular reflex initiated by a significant preload that increases concentric EMG activity, as well as a contribution from the elastic potential of lengthened myofascial tissue.
<table>
 <tbody>
 <tr>
 <td>Practical Application: Pre-stretch to Improve Concentric Force Production:
 <ul>
 <li>Always included a pre-stretch phase during <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercise (no concentric only <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercises).</li>
 <li>Ensure the athlete must overcome the <a id="amortization-phase" data-tip="1546" target="_blank" href="/glossary-term/amortization-phase" class="glossary">amortization phase</a> without assistance from &quot;bouncing&quot; the load off of the floor or rack.</li>
 <li>Progress exercise by increasing pre-stretch intensity; for example, increasing depth jump height.
 <ul>
 <li>Note, studies imply that improvements in concentric force production from eccentric load may be limited to about 50cm depth jumps or 30% of 1-RM upper body strength (conservatively).</li>
 </ul>
 
 </li>
 </ul>
 </td>
 </tr>
 </tbody>
</table>
<img src="https://www.datocms-assets.com/25800/1649705804-jumping.png" title="Dr. Brent Brookbush demonstrating the lateral hop to single leg sagittal plane hop to balance exercise" alt="Lateral hop to single leg sagittal plane hop to balance">
<a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">Lateral</a> hop to single-leg sagittal plane hop to <a id="balance" data-tip="1190" target="_blank" href="/glossary-term/balance" class="glossary">balance</a>.

<ul>
 <li>Contraction Velocity by Fiber Type: In consideration of the following section, it is important to note that research has demonstrated that type IIx myosin <a id="isoform" data-tip="1276" target="_blank" href="/glossary-term/isoform" class="glossary">isoforms</a> have the fastest contraction velocity, followed by type IIa, and then type I fibers. From <a href="https://brookbushinstitute.com/courses/muscle-fiber-types" target="_blank" rel="noopener">Muscle Fiber Types</a>, &quot;Type IIB/X fiber contraction speeds range from 0.94-5.59 fiber lengths per second, which is 49% faster than Type IIA fibers, with fiber force output ranging from 0.95-1.30 Newton meters, which may be 4-percent less force than Type IIA. Type I fibers have contraction speeds ranging from 0.28-1.65 fiber lengths per second, and lower force production per fiber ranging from 0.47-1.01 Newton-meters.&quot;</li>
</ul>

Muscle Fiber Adaptations

<ul></ul>
Studies have investigated the correlation between fiber type proportion and RFD. Smedegaard et al. demonstrated that knee extensor RFD was strongly correlated (63-69%) with type II fiber proportion by cross-sectional area, in a group of 9 untrained men (53). Gregor et al. demonstrated that there was a significant difference between female athletes with more or less than 50% type II fibers when comparing peak <a id="torque" data-tip="1294" target="_blank" href="/glossary-term/torque" class="glossary">torque</a> at faster leg extension speeds (54). And, Thorstensson et al. demonstrated that there was a correlation between the highest speeds produced during concentric knee extensions and the relative area of type II fibers among young healthy males (55). Terzis et al. demonstrated a correlation between triceps brachii type II fiber area and shot-put performance, in male students following 5-weeks of training (56). These studies demonstrate a clear relationship between the proportion of type II fibers and speed/peak power; further, a series of studies by Methentis et al. highlight additional relationships. Methentis et al. demonstrated that <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> trained athletes exhibited the highest <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> conduction velocities, CMJ heights, RFD, and percent of type II and type IIx fibers by CSA, followed by strength-trained athletes who exhibited more mixed values, and the lowest values were exhibited by endurance athletes and sedentary individuals who exhibited similar values (57). Methenitis et al. (2016), also demonstrated that explosive performance is strongly correlated with the conduction velocities of the fastest fibers, again demonstrating a correlation with percent and CSA of type II <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> fibers (58). Last, Methentis et al. (2019) demonstrated a strong correlation between power-trained participants, the proportion and cross-sectional area of type IIx <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> fibers, and the fastest and earliest increases in RFD. Only a moderate correlation was found between non-power-trained individuals, the percent and CSA of type II fibers, and RFD (59). These studies suggest that strength and power-trained athletes exhibit higher proportions of type II fibers and that the performance of power-trained athletes may additionally be correlated with the proportion of type IIx fibers. An interesting case study demonstrates an extreme example of this; Trappe et al. had the opportunity to study the <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> characteristics of a world champion sprinter who is the current indoor world record holder in the 60-m hurdles (7.30 s) and former world record holder in 110-m hurdles (12.91 s). Biopsy of the athlete&apos;s legs had the highest recorded proportion of pure MHC IIx (24%) <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> fibers and a total fast-twitch fiber proportion of 71%. Additionally, the MHC IIx fibers were highly <a id="responsiveness" data-tip="1315" target="_blank" href="/glossary-term/responsiveness" class="glossary">responsive</a> to intense exercise at the gene level (Fn14 and myostatin) (60). Metaxas et al. demonstrated that fiber type proportion or cross-sectional area were not correlated with sprint performance among youth soccer players. This may imply soccer requires a mix of fiber types for <a id="optimal" data-tip="1571" target="_blank" href="/glossary-term/optimal" class="glossary">optimal</a> performance, or that adolescent athletes do not exhibit differentiation or <a id="specificity" data-tip="1224" target="_blank" href="/glossary-term/specificity" class="glossary">specific</a> training adaptations until later in maturity (61). These studies demonstrated that performance of high velocity movement is correlated with an increase in type II fiber proportion and CSA, and power-trained athletes may exhibit significantly higher proportions of type IIx fibers in particular.
<img title="ATPase Staining of a Muscle Cross-Sectional Area" src="https://www.datocms-assets.com/25800/1649648760-muscle-fiber-types.jpg" alt="Muscle fiber types identified through staining">
<h3>Training and Changes in Cross-sectional Area (CSA):</h3>
Several studies have demonstrated that increases in <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> following training are strongly correlated with increases in <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> CSA (hypertrophy). Sanchis-Moysi et al. demonstrated that the dominant leg and arm of professional tennis players exhibited a larger CSA than the non-dominant arm; however, the proportion of <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> types was similar between limbs with a larger proportion of type II fibers in the triceps brachii, and a larger proportion of type I fibers in the vastus lateralis (62). Shoepe et al. compared trained and untrained men, demonstrating that strength, peak <a id="torque" data-tip="1294" target="_blank" href="/glossary-term/torque" class="glossary">torque</a>, and absolute <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> was highly correlated with <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> CSA and fiber type proportion, and were not strongly correlated with intrinsic contractile properties (e.g. single fiber contraction velocity and CA2+ <a id="sensitivity" data-tip="1226" target="_blank" href="/glossary-term/sensitivity" class="glossary">sensitivity</a>) (63). Similarly, Widrick et al. demonstrated that the increases in <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> following 12 weeks of progressive resistance training were strongly correlated with an increase in CSA and peak Ca2+ activated force of all fiber types, and not increases in shortening velocity, fiber type proportion, or qualitative change in the force production capacity of individual fibers (19). Seynnes et al. demonstrated that during a 35-day high-intensity resistance training program (leg extension flywheel), adaptations included an increase in <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> CSA, increase in fascicle length and increase in pennation angle, with significant changes noted as early as the 20th day (64). Bogdanis et al. demonstrated that a combination of low-volume fast eccentric and ballistic jump squat training with <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> jumps in a strength&#x2013;power <a id="post-activation-potentiation" data-tip="1393" target="_blank" href="/glossary-term/post-activation-potentiation" class="glossary">potentiation</a> complex format, resulted in substantial gains in strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> and an increase in CSA of all <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> types, without a reduction in fast-twitch fiber composition (65). Further, Potteiger et al. compared 3x&apos;s/week for 8-weeks of <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> training to <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> training followed immediately by 20 minutes of aerobic activity, demonstrating that both groups made similar improvements in <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> CSA and CMJ performance (66). Conversely, Terzis et al. demonstrated that adding 30-minutes of low-intensity running (60-70% of max heart rate) to a 6 week (3x&apos;s/week) lower body <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training program decreased the improvements made in CSA, intramuscular fiber conduction velocity, counter-movement jump height, and peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> (67). These studies demonstrate that improvements in performance following <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training are highly correlated with increased <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> CSA. Further, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training may be augmented by the addition of maximal strength training in a <a id="post-activation-potentiation" data-tip="1393" target="_blank" href="/glossary-term/post-activation-potentiation" class="glossary">potentiation</a> program, but further research is needed on the potential of aerobic activity to reduce gains made from <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training.
<table>
 <tbody>
 <tr>
 <td>Interesting Note: Both this section and Motor Unit Recruitment Threshold and Ca2+ Sensitivity imply that certain muscle fibers characteristics do not change with training, specifically, increases in single fiber contraction velocity and force production capacity. However, several of the studies in this section contradict studies demonstrating that increased performance was correlated with an increase in CA2+ sensitivity or fiber type proportion (note, an increase in type II fibers would also increase the average CA2+ sensitivity of a muscle). This may imply that short-term (3 months or less) improvements in power are due primarily to increased motor unit recruitment during the early phase contraction and increases in muscle CSA, and that changes in CA2+ sensitivity and fiber type proportion (which may be related) either contribute less to performance, or these changes are the result of long-term habitual training and sport. As discussed in the next section, there is a significant amount of evidence to demonstrate that fiber type proportions due change as a result of training.</td>
 </tr>
 </tbody>
</table>

Fiber Types Proportion and Rate of Force Development

Studies have demonstrated correlations between enhanced performance following <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training and alterations in fiber type proportions and/or an increase in the CSA of <a id="specificity" data-tip="1224" target="_blank" href="/glossary-term/specificity" class="glossary">specific</a> fiber types. Jansson et al. demonstrated that 6 weeks (2-3x of 15-20min/week) of sprint training on a cycle ergometer with 75g per kg bodyweight load decreased type I fibers an average of 9% and increased type IIa fibers and an average of 6% (68). In a similar study, Sjodin et al. demonstrated sprint training on a resisted cycle ergometer for 6 weeks reduced type I fibers, increased type IIa fibers, and further, noted a reduction of type IIx fibers (69). Farup et al. compared resistance training and endurance cycling, demonstrating that both groups exhibited an increase in type IIa fiber CSA and a decrease in type IIx fiber CSA; however, the resistance training groups did exhibit increases in RFD (70). This may imply that the addition of resistance to endurance training results in a shift from type I and type IIx to type IIa fibers. Resistance training appears to result in a similar shift. Andersen et al. demonstrated that a 3-month period of intensive strength and interval training altered fiber type resulting in fewer fibers with only type Ia <a id="isoform" data-tip="1276" target="_blank" href="/glossary-term/isoform" class="glossary">isoforms</a>, as well an increase in fibers that included type IIa <a id="isoform" data-tip="1276" target="_blank" href="/glossary-term/isoform" class="glossary">isoforms</a>. Further, this study demonstrated that most cells with IIx <a id="isoform" data-tip="1276" target="_blank" href="/glossary-term/isoform" class="glossary">isoforms</a> contained type IIa <a id="isoform" data-tip="1276" target="_blank" href="/glossary-term/isoform" class="glossary">isoforms</a> after training (71). Andersen et al. (2010) demonstrated that 14-weeks of resistance training resulted in an increase in maximal strength, type IIa fiber CSA, and also decreased type IIx fiber CSA. The increase in Type I fiber CSA had a positive influence on both early and late RFD; however, the decrease in type IIx fiber CSA negatively influenced early RFD only (72). These studies suggest that strength endurance training or maximal strength training done alone may shift fiber type proportion away from type I and IIx fibers, increasing the number and CSA of IIa fibers.
<h3>High Velocity Training to Retain or Increase Type IIx Fibers:</h3>
The addition of high velocity training may be imperative to maintaining type IIx fiber proportion and CSA. Dawson et al. demonstrated that 16 sprint sessions in 6 weeks improved performance on all speed and endurance tests, and resulted in an increase in the proportion of type II fibers, as well as an increase in phosphorylase, a decrease in citrate synthase, and no significant change in myokinase or phosphofructokinase (73). Zaras et al. demonstrated similar increases in strength, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, and Wingate anaerobic performance following 6 weeks of strength or ballistic-power training; however, strength training resulted in larger increases in CSA and hypertrophy of all fiber types, whereas <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training resulted in hypertrophy of only type IIx fibers (74). Malisoux et al. demonstrated that following 8-weeks of <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> training, athletes exhibited an average increase of 8% in the proportion of type IIa fibers, and an 11% increase in the single fiber CSA of type I fibers, 1o% in type IIa fibers, and 15% in type IIa/IIx fibers. Peak fiber force increased by 35% in type I fibers, 25% in type IIa, and 57% in type IIa/IIx fibers, and there was a significant increase in single-fiber Ca2+ <a id="sensitivity" data-tip="1226" target="_blank" href="/glossary-term/sensitivity" class="glossary">sensitivity</a>, especially in type I fibers (75). Liu et al. compared the change in <a id="isoform" data-tip="1274" target="_blank" href="/glossary-term/isoform" class="glossary">isoform</a> expression (fiber type) following 6 weeks of max strength training versus a combination of max strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training. In the max strength group, type I fiber proportions were similar, type IIa fiber proportions increased, and type IIx fiber proportions decreased. In the combination group type Ia fiber proportions decreased, type IIa fibers increased, and type IIx fibers remained the same (76). Bogdanis et al. demonstrated that a combination of low-volume fast eccentric ballistic squat jumps with <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> jumps in a strength&#x2013;power <a id="post-activation-potentiation" data-tip="1393" target="_blank" href="/glossary-term/post-activation-potentiation" class="glossary">potentiation</a> complex, resulted in substantial gains in strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> and an increase in CSA of all <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> types, without a reduction in fast-twitch fiber composition (77). These studies suggest that high velocity, <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> or ballistic training alone or in conjunction with strength training may result in an increase, or aid in maintaining type IIx fiber proportions, as well as increase the CSA of all fiber types.

Although optimizing IIx fiber proportion and CSA may be beneficial, fiber type proportion is only one of many contributing factors to RFD and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> performance. Ewing et al. compared peak <a id="torque" data-tip="1294" target="_blank" href="/glossary-term/torque" class="glossary">torque</a> and changes in fiber type proportions in groups either performing slow repetitions (1.05 rad for 10 reps) or fast repetitions (4.19 rad for 20 reps) using an isokinetic knee extension dynamometer for 10 weeks (2x/week). The slow group exhibited larger improvements in peak <a id="torque" data-tip="1294" target="_blank" href="/glossary-term/torque" class="glossary">torque</a> at slower tempos, and the fast group improved peak <a id="torque" data-tip="1294" target="_blank" href="/glossary-term/torque" class="glossary">torque</a> at faster tempos. Neither group exhibited changes in fiber type percentages; however, both groups exhibited increases in the CSA of type I and type IIa fibers (78). A study by McGuigan et al. demonstrated that 8 weeks of jump squat training with either 30% or 80% of 1RM resulted in negligible changes in fiber type proportion, despite significant improvements in performance (79). Both of these studies allude to increases in <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> as a result of changes not <a id="specificity" data-tip="1224" target="_blank" href="/glossary-term/specificity" class="glossary">specific</a> to type IIx fibers. Strangely, detraining also increases the proportion of type IIx fibers. Staron et al. demonstrated that after 20 weeks of heavy training, 6 women exhibited an increase in fiber CSA and a shift from type IIx to type IIa fibers. Following 32 weeks of detraining, CSA decreased, but not to pre-training levels, and the proportion of type IIx fibers exceeded pre-training levels. Following 6 weeks of retraining, CSA again increased, type IIx fibers decreased, and another 7 weeks of training continued the same trend until type IIx fibers were no longer found (80). Andersen et al. (2000) demonstrated that following 3 months of heavy resistance training, the proportion of type IIa fibers increased and the proportion of type IIx fibers decreased; however, after 3 months of detraining the proportion of type IIx fibers increased to a proportion greater than exhibited pre-training (81). Andersen et al. (2005) also demonstrated that in previously untrained individuals, 3 months of strength training increased CSA, strength at slow and medium velocities, and EMG activity. Following 3 months of detraining, improvements in CSA were lost, there was a shift toward fewer type I and type IIa fibers, and type IIx fiber proportion and peak <a id="torque" data-tip="1294" target="_blank" href="/glossary-term/torque" class="glossary">torque</a> during faster tempo knee extension increased (82). Hortob&#xE1;gyi et al. demonstrated that 14 days of detraining is probably insufficient to result in a change in fiber type proportion, as only affected eccentric strength and type II <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> CSA decreased, and there was no effect on concentric force production, vertical jump performance, or type I CSA (83). These studies suggest that although the maintenance of type IIx fibers may be <a id="optimal" data-tip="1571" target="_blank" href="/glossary-term/optimal" class="glossary">optimal</a> for maximizing <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, an increase in type IIa fiber CSA and proportion is more likely to follow the training, especially in sports requiring a mix of endurance, strength, and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>. Further, an increase in type IIx fiber proportions is an adaptation noted after detraining (more than 2 weeks), implying that high proportions of type IIx fibers may also be correlated with deconditioning.
<table>
 <tbody>
 <tr>
 <td>Practical Application: Training for Fiber Type
 <ul>
 <li>Strength training or maximal strength training done alone, may shift fiber type proportion away from type I and IIx fibers, increasing the number and CSA of IIa fibers.</li>
 <li>High velocity, <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> or ballistic training alone or in conjunction with strength training may result in an increase, or aid in maintaining type IIx fiber proportions, as well as increase the CSA of all fiber types.</li>
 </ul>
 </td>
 </tr>
 </tbody>
</table>

Studies demonstrate a relationship between pennation angle, fascicle length, CSA (<a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> architecture), and performance of high velocity activity. McMahon et al. demonstrated that increased vastus lateralis CSA, and <a id="medial" data-tip="1568" target="_blank" href="/glossary-term/medial" class="glossary">medial</a> gastrocnemius CSA and pennation angle, were correlated with 1-RM <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> clean performance (84). Secomb et al. demonstrated that vastus lateralis CSA and an increase in <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> gastrocnemius pennation angle were related to improved performance in the CMJ, squat jump, and isometric mid-thigh pull in 14 surf athletes; however, musculotendinous stiffness accounted for much of the variation between athletes (23). Hamza et al. demonstrated that the pennation angle of the gastrocnemius was strongly correlated with reaction time and acceleration in female sprinters (85). Monte et al. demonstrated increased fascicle length, greater <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> CSA and decreased pennation angle of lower extremity muscles were correlated with greater force production and ability to accelerate in male sprinters (86). Mizuno et al. compared 37 male 100m sprinters with times of 10:00 -10:90 seconds to times of 11.00 to 11.70 seconds, demonstrating that the faster group exhibited a relative increase in <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> CSA, increase in fascicle length, and a decrease fascicle angle in the gastrocnemius and vastus lateralis (87). Kipp et al. demonstrated that velocity and peak force were correlated with shorter fascicle length, decreased pennation angles, and greater CSA of the gastrocnemius in 10 division-1 volleyball players (88). And, Seynnes et al. demonstrated that a 35-day high-intensity resistance training program increased performance; as well as <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> CSA, fascicle length, and pennation angle by the 20th day of training (64). Although these studies demonstrate a strong correlation between <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> architecture and performance, it is worth noting that the correlations between pennation angle and performance are not consistently in one direction, and further, these studies fail to differentiate between pennation angle, CSA, and fascicle length when correlating with performance. The study by Seynnes et al. suggests it may not matter, as resistance training increases all of these attributes without a need for an intervention that targets one <a id="specificity" data-tip="1224" target="_blank" href="/glossary-term/specificity" class="glossary">specific</a> attribute over the others.
<img src="https://www.datocms-assets.com/25800/1644344290-1119_muscles_that_move_the_humerus_a.png" title="Note the direction and shape of the various muscle fibers" alt="The shapes and directions of various upper body muscles">
Additional studies suggest <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> architecture and performance are not as strongly correlated as the previously mentioned studies. Blazevich et al. compared 5 weeks of sprint and jump training alone, to sprint and jump training with either front hack squats or back squats, demonstrating that strength, sprint, and jump performance were similar between all groups, despite a small decrease in vastus lateralis fascicle angle in the front hack squat and back squat groups (89). Abe et al. compared sprinters, long-distance runners, and controls, demonstrating sprinters exhibited increased <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> CSA, longer fascicle lengths, and decreased pennation angles in gastrocnemius and vastus lateralis samples. Controls and long-distance runners exhibited similar <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> thickness, fascicle length, and pennation angle (90). However, in a follow-up study comparing sprinters, Abe et al. demonstrated a correlation between relative fascicle length and sprint performance; however, no correlation could be made between pennation angle and sprint performance (91). Aagaard et al. demonstrated that 14 weeks of heavy resistance training resulted in an increase in CSA, which was strongly correlated with changes in pennation angle, and further, the combination of CSA and changes in pennation angle were more strongly correlated with the improvements in strength than CSA or pennation angle alone (92). Cormie et al. compared adaptations of stronger and weaker groups trained 3x&apos;s/week for 10 weeks, demonstrating significant changes in performance, force/velocity curve, mechanics, and neural activation, but no significant changes in <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> architecture (93). Blackwood et al. demonstrated that the pennation angle of the quadriceps was similar between right and left legs and between resistance-trained and untrained controls, despite significant differences in strength, lean mass and fat mass between dominant and non-dominant legs and trained versus untrained individuals, suggesting that pennation angle was not correlated with the differences in strength (94). Coratella et al. demonstrated that in 21 amateur cyclists, 85% of the variance in peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> could be attributed to vastus lateralis and gastrocnemius CSA, and fascicle length was predictive of time to peak power; however, pennation angle did not have a strong enough correlation to predict any differences in performance (95). These studies demonstrate that pennation angle when grouped with CSA and fascicle length has a correlation with performance; however, pennation angle alone likely has little or no correlation. Based on the current available evidence, it seems likely that CSA is correlated with performance and that increases in CSA (hypertrophy) may incidentally alter pennation angle, and/or fascicle length.
Studies on stretching, pennation angle, and performance also exhibit weak or no correlation. A study by Park et al. demonstrated that acute changes in pennation angle of the gastrocnemius resulting from stretching were similar to those seen with active exercise (96). And, Miskowiec et al. demonstrated that stretching had no lasting effect on the pennation angle of the gastrocnemius, and therefore, no correlation with the reduction in MVC was noted following the stretch (97). Although pennation angle may have interesting implications for understanding the force generation capabilities of <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a>, based on these studies and the study Seynnes et al. (64), it likely has little if any practical application.

Several studies have investigated the relationship between enzymes, <a id="hormone" data-tip="1268" target="_blank" href="/glossary-term/hormone" class="glossary">hormones</a>, and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> performance. It should be noted that this paragraph only includes research that specifically investigated high velocity activity and <a id="hormone" data-tip="1268" target="_blank" href="/glossary-term/hormone" class="glossary">hormones</a>. Studies related to <a id="hormone" data-tip="1268" target="_blank" href="/glossary-term/hormone" class="glossary">hormones</a> and hypertrophy, or <a id="hormone" data-tip="1268" target="_blank" href="/glossary-term/hormone" class="glossary">hormones</a> and maximal strength are discussed in other courses. Costill et al. obtained fiber samples from the gastrocnemius of 17 female and 23 male track and field athletes and compared them to 10 untrained males and 11 untrained females. Findings demonstrated that increased succinate dehydrogenase (SDH) activity was strongly correlated with VO2max, increased average type I fiber proportion, and was higher in endurance athletes. Lactic dehydrogenase was correlated with an increased proportion of type II fiber and was higher in sprint athletes. Strength athletes exhibited a larger variety of fiber compositions, but relatively low enzyme levels (98). Argus et al. demonstrated that over a rugby season, players exhibited a small increase in testosterone and testosterone to cortisol ratio, as well as increases in strength and power; however, no correlations were identified between <a id="hormone" data-tip="1266" target="_blank" href="/glossary-term/hormone" class="glossary">hormone</a> levels and individual differences in <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> performance (99). In a two-year study of 9 elite weight lifters, Hakkinen et al. demonstrated a correlation between the amount of increase in resting testosterone and changes in average concentric power; this may imply long-term changes to the pituitary and possibly hypothalamic activity (100). Stoessel et al. demonstrated that female weightlifters were leaner and more powerful (vertical jump and static vertical jump performance), but had similar resting serum <a id="hormone" data-tip="1268" target="_blank" href="/glossary-term/hormone" class="glossary">hormones</a>, lipid, and glucose concentrations when compared to untrained controls (101). These studies suggest that experience may have an effect on enzyme levels and power; however, the correlation between experience, altered <a id="hormone" data-tip="1266" target="_blank" href="/glossary-term/hormone" class="glossary">hormone</a> levels, and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> is likely weak.
Additional studies have investigated the effects of training on performance and changes in <a id="hormone" data-tip="1266" target="_blank" href="/glossary-term/hormone" class="glossary">hormone</a> and enzyme levels. Dawson et al. demonstrated that 16 sprint sessions in 6 weeks (30-80meters, 90-100% max speed, 20-40 sprints/session) resulted in improvements on all speed and endurance tests, as well as an increase in the proportion of type II fibers, increased phosphorylase, and a decrease in citrate synthase, but no significant change in myokinase or phosphofructokinase (73). Crewther et al. demonstrated that 40 seconds of sprint cycling before a workout (4-week program), with the intent of affecting resting testosterone and cortisol levels, had no effect on strength or power; however, resting levels of testosterone and cortisol did correlate with individual improvements in strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> (102). An earlier study by Crewther et al. demonstrated that lower extremity cycle sprints, but not upper extremity cycle sprints, increased testosterone while cortisol levels remained unchanged. Lower body and upper body 1RM strength increased following cycle sprints, perhaps due to the increase in circulating testosterone; however, there was no effect on peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> during bench press throws or squat jumps (103). H&#xE4;kkinen et al. demonstrated that 7 females participating in a 16-week <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training program exhibited no statistically significant changes in mean concentrations of serum testosterone, free testosterone, follicle-stimulating <a id="hormone" data-tip="1266" target="_blank" href="/glossary-term/hormone" class="glossary">hormone</a> (FSH), luteinizing <a id="hormone" data-tip="1266" target="_blank" href="/glossary-term/hormone" class="glossary">hormone</a>, cortisol, progesterone, estradiol, or sex hormone-binding globulin. However, individual levels of both mean total and free testosterone correlated significantly with improvements in early force development and total force production in the force-time curve (104). Peltonen et al. compared responders and non-responders following 10 weeks of maximum strength training followed by 10 weeks of <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training, demonstrating that responders had higher levels of free testosterone; despite testosterone levels decreasing slightly during the maximum strength phase in the responder group (105). Last, Elliot et al. compared adaptations following 8 weeks of progressive strength training and progressive <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training to controls (no training), demonstrating similar results for both strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> trained groups including increased 1-RM squat strength, hypertrophy of type I, IIa, and IIb fibers, type IIb fibers decreased as a percentage, increased mTOR and RICTOR mRNA expression, 4EBP&#x2010;1 decreased after training, calcineurin levels did not change after training while calcipressin increased, RAPTOR increased for both groups but to a greater extent after strength training. This study demonstrated both training programs resulted in similar performance improvements; however, there was a trend toward greater hypertrophy&#x2010;related gene expression and <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> hypertrophy for the strength group (106). Again, these studies seem to imply that increases in enzymes (phosphorylase, decreases in citrate synthase) are likely following training; however, the effect of <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training and <a id="hormone" data-tip="1266" target="_blank" href="/glossary-term/hormone" class="glossary">hormone</a> levels is less clear (strength training resulting in more hypertrophy-related gene expression). Resting or mean levels of testosterone may have an effect on the amount of improvement made during training.
<table>
 <tbody>
 <tr>
 <td>Practical Application: Muscle Architecture, Hormones, and Enzymes
 <ul>
 <li>To date, there is little, if any evidence, that a training type or training volume can be used to optimize <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> architecture, <a id="hormone" data-tip="1268" target="_blank" href="/glossary-term/hormone" class="glossary">hormones</a>, or enzymes with the intent of improving <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> performance.</li>
 <li>Resting testosterone levels may be predictive of the amount of improvements made and/or performance of elite athletes who have participated in long-term training programs; but again, this does not seem to be strongly correlated with a particular type of training.</li>
 </ul>
 </td>
 </tr>
 </tbody>
</table>

<h3>General Correlation Between Strength and Power</h3>
Several studies have demonstrated a relationship between maximum strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>. Wisloff et al. demonstrated a strong correlation between 1-RM half-squat strength and 30m sprint times, 10M shuttle run times, and vertical jump height (107). Sleivert et al. demonstrated a correlation between 5m time during a sprint <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a> and peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> development during jump squats, split squats, and back squats between 30 - 70% 1-RM (108). Several studies have compared the performance of weaker and stronger athletes. Mcbride et al. demonstrated individuals who could 1-RM squat (to 70&#xB0; knee flexion) with 2.1 times body weight were significantly faster than individuals who could squat 1.9 times bodyweight for 10m and 40m sprint times, but not 5 meter sprint times (109). Thomas et al. demonstrated higher peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, RFD, and instantaneous force during MVIC were correlated with peak force, but not peak height during vertical jump; however, stronger athletes did jump higher than weaker athletes (110). Two additional studies demonstrate that stronger athletes were less affected by the addition of external load. Stone et al. demonstrated a correlation between individuals with the largest relative 1RM squat and their ability to produce peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> with larger loads during a loaded jump; weaker individuals produced peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> at approximately 10% 1RM, whereas stronger individuals produced peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> at 40% 1RM (111). Further, Kraska et al. demonstrated that stronger athletes jump higher than weak athletes, and jump height decreases less with added load (112). These studies demonstrate a moderate correlation between increased strength and increased RFD; however, further studies demonstrate stronger relationships when additional factors are considered. Increased strength is correlated with the ability to maintain RFD at higher loads.
<h3>Sport and Athletic Experience:</h3>
Studies investigating various groups of athletes and their capacity to produce <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> suggest adaptations are <a id="specificity" data-tip="1224" target="_blank" href="/glossary-term/specificity" class="glossary">specific</a> to sport, training demands, and experience. Mcbride et al. demonstrated that powerlifters, Olympic lifters, and sprinters exhibit performance characteristics that match their sport. All groups performed better on all tests than controls; however, sprinters performed better than all groups on the vertical jump <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>, Olympic lifters performed better than powerlifters on vertical jump and jump squat tests, and powerlifters performed better on 1-RM squat tests than other groups (113). Ugrinowitsch et al. demonstrated that the vertical jump heights of power/track athletes were higher than the vertical jump heights of body-builders or recreationally active individuals, 1-RM was correlated with jump height in <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> athletes and body-builders but not active individuals, and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> athlete jump heights were correlated with counter-movement excursion and not RFD (114). Carlock et al. demonstrated that vertical jump performance was correlated with a weightlifter&apos;s ability and experience, suggesting that both chosen sport and experience play a role in developing <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> (115). In summary, max strength is correlated with power; however, peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> is highest in more experienced athletes and athletes participating in <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> sports.
<h3>Dynamic, Closed-chain &amp; Relative Load</h3>
Although a moderate correlation between certain measures of max strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exists, further studies demonstrate that stronger correlations exist when additional factors are considered. Nuzzo et al. demonstrated that relative (to body weight) squat and clean strength, but not absolute strength, were correlated with CMJ performance (116). Blackburn et al. demonstrated that closed <a id="kinetic-chain-2" data-tip="1544" target="_blank" href="/glossary-term/kinetic-chain-2" class="glossary">kinetic chain</a> strength (squat) was correlated with vertical jump and long jump performance, but open <a id="kinetic-chain-2" data-tip="1544" target="_blank" href="/glossary-term/kinetic-chain-2" class="glossary">kinetic chain</a> strength (leg extension) was minimally correlated (117). Miyaguchi et al. demonstrated that maximal upper body <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> output was correlated with 1-RM bench press, and only minimally correlated with 1-RM maximal voluntary isometric contraction (MVIC) (118). Further, Duchateau et al. compared 3 months of moderate, isometric, or dynamic voluntary strength training. Findings demonstrate that isometric exercises increased peak force and peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> when using higher loads; however, only dynamic contractions had a significant impact on RFD and movement velocity (119). These studies demonstrate that the correlation between high velocity activity and strength is higher when strength is measured relative to bodyweight, is dynamic, and closed-chain.
<h3>Velocity Matters:</h3>
Further studies demonstrate that the velocity of the movement used to measure strength has an influence on the strength of the correlation between strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>. Baker et al. demonstrated a significant correlation between 3-RM strength and max power; however, a high level of variability exists, especially for the upper body, suggesting <a id="specificity" data-tip="1224" target="_blank" href="/glossary-term/specificity" class="glossary">specific</a> measures may be necessary. This study, also demonstrated that the clean was more correlated with lower body <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> than a squat (120). Mayhew et al. compared 1-RM bench press, bench press throw peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, and seated shot put before and after weight training 2x&apos;s/week for 12 weeks. Training increased 1-RM and bench press <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> at all loads, with peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> demonstrated at 40 - 50% 1RM; however, insignificant improvements in the seated shot-put were noted (121). Thomas et al. demonstrated higher peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, RFD, and instantaneous force during MVIC were correlated with peak force, but not peak height during the vertical jump (110). Haff et al. demonstrated that isometric peak force correlated with peak force; and isometric RFD was correlated with peak force and peak RFD during <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> cleans at 80, 90, and 100% 1RM (122). Cronin et al. demonstrated that squat jumps and CMJ, but not maximal strength, were strongly correlated with first-step quickness, acceleration, or max speed at 30 meters (123). Sheppard et al. demonstrated that force-velocity characteristics of the leg extensors in well-trained jumping athletes were a <a id="reliability" data-tip="1795" target="_blank" href="/glossary-term/reliability" class="glossary">reliable</a> indicator of performance (peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, relative peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, and peak force), and that an intensive 12-week training program may result in significant improvements in performance and improve <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a> results (124). These studies imply that the relationship between strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> is weak when the strength measure does not sufficiently approximate the <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> movement pattern. Further, higher velocity lifts (e.g. Olympic Lifts) are more strongly correlated with <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> than slower lifts.
<img src="https://www.datocms-assets.com/25800/1649706228-chest-pass.png" title="The plyometric medicine ball chest pass, an upper body power exercise" alt="A medicine ball chest pass used as an upper body power exercise">
<h3>Change of Direction:</h3>
The relationship between max strength and the ability to change directions has been investigated in various athletic populations. Spiteri et al. demonstrated that stronger individuals exhibited a significantly faster stride velocity after a 45&#xB0; change of direction when compared to weaker athletes (125). Spiteri et al. demonstrated that in a group of female basketball, the fastest change of direction and agility <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a> scores were correlated with more isometric and eccentric strength, but not concentric strength (126). Hori et al. divided semiprofessional Australian Rules football players into top and bottom half groups based on their relative 1-RM hang <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> clean strength, demonstrating a correlation between the top half group and higher maximum strength, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, jumping, and sprinting. However, there was no significant difference between groups in 5-5 change of direction time (127). Freitas et al. demonstrated that stronger and more powerful rugby players were significantly faster during straight trajectory sprint testing but relatively slower at changing directions (128). Young et al. demonstrated that depth jump height and sprint acceleration were correlated with the change of direction and agility, but 3RM max half-squat strength was not for Australian rules football players (129). Keiner et al. compared strength training and soccer practice to soccer practice alone in young athletes over a 2-year period, demonstrating the addition of strength training had a significant effect on the change of direction speed (130). However, Prieske et al. compared 6 weeks of either resisted sprints or traditional <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training, demonstrating that both programs resulted in similar improvements in 20m sprints, but did not improve change-of-direction speed, jump height, or <a id="balance" data-tip="1190" target="_blank" href="/glossary-term/balance" class="glossary">balance</a> performance (131). This research suggests that long-term adaptations to strength training in conjunction with sports training may improve change of direction speed; however, this relationship is likely limited to the degree of the change in direction, and it seems likely that there is a limit to the amount of strength can improve change of direction speed.

Training Modalities

As mentioned above, there is a correlation between maximal strength and RFD; the following studies demonstrate the efficacy of strength training to improve <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> performance. Comfort et al. demonstrated that 4 weeks of moderate load resistance training, followed by 4-weeks of high load resistance training, resulted in significant increases in multi-joint force production during the early part of the concentric phase (132). Barjaste et al. investigated the results from a simple periodization program including a 6-week anatomical phase (65-75% of 1-RM, 11 exercises/session) followed by a 6-week maximal strength phase (85-95% of 1RM, 3 to 4 exercises/session). The findings demonstrate that the largest improvements in 1-RM and vertical jump height were gained after the first (anatomical) phase (133). Moss et al. demonstrated 9 weeks of 3x/week elbow flexor training with 90% of 1RM had a larger impact on <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> and 1RM strength than 35% and 15% of 1RM. Note, this study used pre-set rep schemes, implying that groups using less load did not train to failure (134). Toji et al. and Kaneko et al. investigated the impact of 8 weeks of training (3x/week) with various combinations of 30%, 60%, and 100% of 1RM loads, demonstrating that groups including maximal load training exhibited greater increases in <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> (135, 136). These studies likely demonstrate that significant improvement in <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, especially force production during the early phase of the concentric contraction, may be achieved with moderate load strength training; however, incorporating near maximal loads is likely ideal for <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> development.
Additional studies demonstrate that strength training may improve <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> performance, even when added to in-season training for sport. Sander et al. demonstrated that the addition of strength training (simple periodization of hypertrophy and <a id="intramuscular-coordination" data-tip="1667" target="_blank" href="/glossary-term/intramuscular-coordination" class="glossary">intramuscular coordination</a> blocks), 2x/week for 2 years to an elite soccer training program, resulted in significant improvements in 1-RM strength and linear speed when compared to elite soccer training alone over the same time period (137). Jakobsen et al. demonstrated that the addition of maximal strength training to recreational soccer, increased CMJ height including RFD, shortened CMJ take-off time, peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, increased rate, and peak EMG of calf and quadriceps, and increased quadriceps CSA (138). Similarly, Chelley et al. demonstrated that junior soccer players performing heavy back squats for 2 months (2x/week) exhibited improvements in peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> during a cycling force-velocity <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>, jump height, and first 5m sprint time; however, in this study, these improvements were exhibited without significant increases in CSA (139). Styles et al. demonstrated that a simple in-season strength training program for 6-weeks (2x/week at 85&#x2013;90% 1RM), increased maximal squat strength and short sprint performance for professional soccer players (5, 10, 20m) (140). And, Baker et al. demonstrated that over a 4-year training period, sub-elite rugby players improved strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> more than elite rugby players (rank based on the league), suggesting that the rate of improvement decreases as a player achieves elite levels of play (141). In summary, the addition of strength training to an in-season training program may enhance attributes that may be beneficial to sports performance, including acceleration, linear speed, strength, CMJ height, and peak power; however, the amount of improvement made from strength training is likely to decrease with experience.

Several studies have demonstrated that <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training is effective for increasing RFD and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> performance. Winchester et al. followed a 3-month resistance training program, with an additional 8 weeks of jump squat training, using a periodized program including loads between 26 and 48% of 1RM, and compared outcomes to controls (no training). The jump squat group significantly increased RFD and peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> during jump tests, without changes in peak force 1RM or <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> type proportion (142). Kyr&#xF6;l&#xE4;inen et al. demonstrated that 15 weeks of <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training resulted in an increase in vertical jump height and RFD during knee extension and jump tests, however, no changes were observed in maximal voluntary isometric contraction (MVIC), <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> activity, or <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> fiber&#x2010;type proportions (143). Cormie et al. compared groups divided on the basis of strength following 10 weeks (3x/week) of training including maximal-effort jump squats with 0% - 30% 1-RM. All groups exhibited significant improvements in force-velocity relationship, jump mechanics, and neural activation, without changes in <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> architecture. There was a trend toward stronger lifters exhibiting the largest improvements in jump performance (144). Malisoux et al. demonstrated that 8 weeks of maximal effort stretch-shortening cycle (SSC) exercise (jump training) resulted in an average increase of 12% in force production, 13% in vertical jump height, and single-fiber cross-sectional area (CSA) increases of type I, IIa, and hybrid IIa/IIx fibers of 23%, 22% and 30% and maximal shortening velocity increases of 18%, 29%, and 22% (145). In summary, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training results in significant increases in RFD and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> performance, and often improvements occur without concurrent increases in strength, hypertrophy, or changes in pennation angle. This likely implies that adaptations are primarily neuromuscular. Note, stronger athletes may benefit more from <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training than weaker athletes.
Additional studies demonstrate significant improvements in peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> when ballistic training is added to the training of athletes. Alkjaer et al. demonstrated that following 4 weeks of intensive drop jump training in well-trained athletes, maximal jump height increased by 11.9%, jumping height/contact time improved by 16.2%, combined ankle and knee joint peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> increased by 7%, pre-activity in the <a href="https://brookbushinstitute.com/courses/soleus" target="_blank" rel="noopener">soleus</a> <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> decreased 16%, and <a href="https://brookbushinstitute.com/courses/soleus" target="_blank" rel="noopener">soleus</a> H-reflex decreased while the <a href="https://brookbushinstitute.com/courses/soleus" target="_blank" rel="noopener">soleus</a> V-wave increased significantly at 45 milliseconds after touchdown (146). Balsalobre-Fernandez et al. demonstrated that the addition of 8 training sessions, consisting of 5 sets of 8 jump squats with a load adjusted for peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, resulted in a significant increase in strength and acceleration in 7 high-level 400-meter hurdlers (147). Chelly et al. demonstrated that the addition of <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> training (hurdle and depth jumping) to in-season elite soccer conditioning resulted in significant increases in <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> output, jump height, and sprint times when compared to controls (148). Matavulj et al. demonstrated that the addition of depth jumps during &quot;normal&quot; midseason junior basketball training, 3x&apos;s week for 6-weeks improved vertical jump performance; however, no difference was noted between 50cm and 100cm depth jump groups (149). Finally, Newton et al. demonstrated that 11 collegiate female volleyball players exhibited a 5.4% decrease in average approach jump and reach height during an in-season training period (start of the season to midseason); however, they exhibited a 5.3% increase in jump and reach height when ballistic training in-season (midseason to end of the season) was inserted with a concurrent decrease in heavy resistance training (150). These studies suggest that the addition of ballistic training to an athletes program may significantly increase variables associated with peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, and replacing some in-season max strength training with ballistic training may even reduce the decrease in <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> performance noted over the course of in-season play.
<img title="Dr. Brent Brookbush demonstrating a single-leg box jump" src="https://www.datocms-assets.com/25800/1649512881-hop-to-single-leg-jump.png" alt="A single-leg box jump exercise for lower body power">

Strength training and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training have both exhibited efficacy for improving the performance of high-velocity activities; however, the pursuit of <a id="optimal" data-tip="1571" target="_blank" href="/glossary-term/optimal" class="glossary">optimal</a> program design and/or time constraints may force the selection of one over the other. Unfortunately, research suggests that <a id="optimal" data-tip="1571" target="_blank" href="/glossary-term/optimal" class="glossary">optimal</a> selection is nuanced, and may depend on several factors. Blattner et al. compared 8 weeks (3x/week, 3 sets/10 reps) of progressive <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> training (weighted depth jumps) and progressive isokinetic training (leg press), demonstrating similar improvements in vertical jump-and-reach height in both groups (151). Cormie et al. demonstrated that both maximal strength and ballistic training improved eccentric variables, which resulted in significant improvements in concentric force production, regardless of whether an individual was weaker or stronger to start the program (152, 153). Holcomb et al. compared a modified <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> depth jump program, conventional <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> depth jump program, countermovement jump program, a weight training program, and no training at all (control group) for 8 weeks (3x/week), and all programs resulted in significant, but similar increases in <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> and vertical jump height (154). These studies demonstrate that strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training have similar efficacy for many athletes and measures of power; however, additional studies highlight additional considerations.
The <a id="specificity" data-tip="1223" target="_blank" href="/glossary-term/specificity" class="glossary">specificity</a> of adaptation may be worthy of consideration when planning a training program. Zaras et al. demonstrated similar increases in strength, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, and Wingate anaerobic performance following 6 weeks of strength or ballistic-power training; however, strength training resulted in larger increases in CSA and hypertrophy of all fiber types, whereas <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training resulted in hypertrophy of only type IIx fibers (155). Loturco et al. compared the performance of 23 male soccer players after random allocation to 4 weeks of jump squat training or half squat training, demonstrating that jump squat training is more effective for reducing acceleration time, half squats are more effective for improving squat jump performance, and both programs were equally effective for improving linear speed (156). Young et al. demonstrated that weaker athletes saw improvement in 1RM and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> output following heavy or ballistic bench press protocols; however, stronger athletes did not achieve the same increases in peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> from heavy bench press training and benefited more from the ballistic bench press (157). Hawkins et al. demonstrated that trained individuals exhibited larger improvements during high velocity performance measures (e.g. vertical jump <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>) following high velocity training (<a id="plyometric" data-tip="1296" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometrics</a> and Olympic lifts), and exhibited larger increases in strength measures (1RM) following loaded training (Oly and weight lifting) (158). These studies suggest that despite a significant amount of overlap in performance improvements, there are subtle differences in the improvements made from strength or high-velocity training that match the demands imposed by the training program.
Additional studies demonstrate a more dramatic difference between the two training modalities. Newton et al. compared squat jump training to 6RM squat and leg press exercises, following a preseason volleyball on-court and resistance training program, demonstrating that squat jump training had a significant effect on vertical jump performance while strength training did not (159). Vissing et al. compared 8 weeks of progressive resistance training or <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> training in a group of untrained men, demonstrating similar increases in strength for leg press and knee extensions; however, knee flexion increased by nearly 50% more in the resistance training group, while vertical jump height, maximal <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, and ballistic incline leg press increased significantly in the <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> group. Interestingly whole <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> size increased similarly in both groups as measured by MRI; however, biopsies showed <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> CSA of type I and type IIa fibers only increased significantly in the progressive resistance training group (160). The results of these studies demonstrate relatively dramatic differences between groups; however, again the adaptations match the demands imposed by the training program.
Two additional studies suggest that the effects of <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training may have a larger impact on maximal strength than strength training has on <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>. Dorrell et al. demonstrated that velocity-based training and %1-RM strength training had a nearly equal effect on 1-RM strength, and only velocity-based training had a significant impact on vertical CMJ height in a group of trained men (161). Baynard et al. demonstrated that velocity-based training resulted in higher velocities, and achieved the same force output as % of 1-RM based training with lower loads and potentially less mechanical stress (162).
These studies demonstrate that both strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training may result in significant improvements in power; however, as might be expected <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training is likely more beneficial than strength training for improving high-velocity tasks, especially for individuals with training experience. Further, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training may have a larger impact on strength than strength training has on <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>.

Several studies have compared the combination of strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training to strength or <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training alone. de Villarreal et al. compared heavy squat training, to power-optimized squat training, to loaded CMJ, to <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> training, to a combination of these training methods, demonstrating that significant improvements in max RFD were exhibited by all groups except the heavy squat training group (163). Harris et al. compared 9 weeks (4xs/week) of strength training, <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training, or mixed strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training. The results demonstrated the <a id="specificity" data-tip="1223" target="_blank" href="/glossary-term/specificity" class="glossary">specificity</a> of adaptation in the strength only (squat, 1/4 squat, midthigh pull, MK) and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> only (1/4 squat, midthigh pull, VJ, MK, SLJ) groups; however, the mixed strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> group demonstrated improvements on all tests (164). Adams et al. compared 7 weeks (2x/week) of training with a periodized squat program, <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> program, or mixed program, and although all programs resulted in a significant increase in the vertical jump, the mixed program resulted in significantly larger increases in performance (165). Cormie et al. compared comparing 7 sets/6 reps of jump squats with body mass only, to another group performing 5 sets/6 jump squats and 3 sets/3reps of squats with 90% of 1-RM. The total work performed by each group was equal throughout the 12-week program. The squat jump only group improved on squat jumps from 0 - 20kg of external load, while the combined group improved equally at low loads, and also improved at loads up to 80kg (highest load tested) (187). Fatouros et al. compared no activity controls to <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> training, weight training, and a combination of <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> and weight training based on vertical jump performance, mechanical <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, flight time, and maximal leg strength. Although all training groups demonstrated significant improvement, the combined group significantly outperformed the other groups (166). From these studies, it may be implied that a combination of strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training is ideal when compared to either strength or <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training alone.
Optimizing program design may require the consideration of additional factors. As mentioned above, Tricoli et al. compared 8-weeks of heavy resistance training and Olympic lifting to heavy resistance training and vertical jump training to non-training controls. Both training groups combined strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> and improved on all measures when compared to controls; however, the Olympic lifting group improved more on squat jump, vertical jump and 10m sprint testing, and the vertical jump testing group performed better on the 1-RM half squat (167). An RCT by Faude et al. demonstrated that the addition of a 7-week combined strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training program during the soccer season resulted in significant improvements in 1-RM strength, RFD, and jump height when compared to controls; however, no effect was noted for agility or sprint times (168). These studies imply that although the combination of strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training is effective, the <a id="specificity" data-tip="1223" target="_blank" href="/glossary-term/specificity" class="glossary">specificity</a> of the modalities used must still be considered. Comfort et al. demonstrated that a rugby league pre-season training program including 4 weeks of strength, followed by 4 weeks of <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training, had a significant effect on 5, 10, and 20m sprint times (169), potentially suggesting that strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training may be performed in separate mesocycles. Bogdanis et al. demonstrated that a combination of low-volume, fast eccentric, and ballistic jump squat training combined with <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> jumps in a strength/power <a id="post-activation-potentiation" data-tip="1393" target="_blank" href="/glossary-term/post-activation-potentiation" class="glossary">potentiation</a> complex format, resulted in substantial gains in strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> and an increase in CSA of all <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> types, without a reduction in fast-twitch fiber composition (77). This could be an important consideration, as mentioned above, strength training alone has a tendency to shift fiber type proportion from type IIx to type IIa. Finally, Ronnestad et al. compared the addition of 7 weeks of strength training or strength training and <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> training to 6-8 soccer sessions per week, demonstrating that the addition of <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> activity did not result in any additional benefits in a variety of strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> tasks (170). In summary, these studies suggest that the combination of strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training is effective, when done simultaneously or in concurrent phases, and may be beneficial for maintaining type IIx fiber proportion; however, <a id="specificity" data-tip="1223" target="_blank" href="/glossary-term/specificity" class="glossary">specificity</a> of the intervention should be considered, as well as the amount of high-velocity activity already included in sport or practice.
<table>
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 <td>Practical Application: Choosing Phases
 <ul>
 <li>Strength Training: Moderate load strength training may be beneficial (especially in novice lifters); however, incorporating near maximal loads is likely ideal for <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> development. Improvements from strength training have been noted pre-season and in-season.</li>
 <li>Power Training: Power training is likely more beneficial than strength training for improving high-velocity tasks, especially for individuals with training experience. <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">Power</a> training may improve performance when performed pre-season, or in-season when used to replace some max strength training with the intent of decreasing the reduction in <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">Power</a> noted over the course of in-season play.</li>
 <li>Combined Training: The combination of strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training is likely more beneficial than either strength or <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training alone; however, the amount of high-velocity activity already included in sport and/or practice must be considered.</li>
 </ul>
 </td>
 </tr>
 </tbody>
</table>
<img title="Dr. Brent Brookbush demonstrating a power pushup exercise" src="https://www.datocms-assets.com/25800/1649512074-powerpushup-1.jpg" alt="Power pushups used to improve upper body power production">

Here the term intensity is being used as it is conventionally used in exercise science, as the variable denoting changes in external load, velocity, or the application of force. Research demonstrates that load and velocity play a significant role in the gains achieved from <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training.
<h3>Specificity:</h3>
Several studies allude to <a id="specificity" data-tip="1224" target="_blank" href="/glossary-term/specificity" class="glossary">specific</a> adaptations to imposed demands (SAID Principle) relative to the load and velocity selected for <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercises. Lesinski et al. compared an in-season progressive strength endurance program (slow tempo, 50-60% of 1-RM; 20-40 repetitions) to a <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training program (high velocity, 50-95% of 1-RM; 3-8 repetitions), demonstrating that endurance training resulted in a larger increase in agility, and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training resulted in a larger increase in 1-RM leg press, depth jump height, and 10 - 20m sprint performance (171). Jones et al. compared 10 weeks (4x/week) of lower body training using maximal concentric velocity with loads of either 40-60% of 1-RM or 70-90% of 1-RM. The lighter load (and faster rep) group exhibited larger improvements in peak velocity and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, and the heavier load (and slower rep) group exhibited larger improvements in 1-RM strength (172). Similarly, Loturco et al. compared 20 soccer players randomly assigned to 6 weeks of a jump squat training program with either higher weight and lower velocity or lower weight and higher velocity. Both groups made improvements on all tests; however, the higher weight group exhibited larger improvements in 1RM strength and mean propulsive velocity during jump squats with 50% or more of body weight, and the lower weight group demonstrated greater improvements in speed at 5, 10, and 20 m sprints, as well as mean propulsive velocity with jump squats up to 40% of body weight (173). Tricoli et al. compared 8 weeks of heavy resistance training and Olympic lifting to heavy resistance training and vertical jump training, to controls not participating in training, demonstrating that both training groups improved on all measures; however, the Olympic lifting group improved more on squat jump, vertical jump and 10m sprint testing, and the vertical jump testing group performed better on the 1-RM half squat (167). These studies suggest that training that focuses on unloaded or lightly loaded repetitions that maximize speed is likely more beneficial for agility and maximal velocity tasks, and heavier repetitions may be more beneficial for improving loaded ballistic motions like Olympic lifting or perhaps overcoming the inertia of linear acceleration.
<h3>Load:</h3>
Research suggests that external load may have a significant effect on adaptations to <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training. Nuzzo et al. demonstrated that trained and untrained men produced the greatest peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> during body-weight squat jumps, when compared to assisted (less than body weight) or loaded squat jumps (175). Cormie et al. demonstrated that peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> was achieved using no load during squat jumps, 56% of 1-RM during conventional squats, and 30 - 40% of 1-RM during cleans (176). Garhammer et al. used a force plate to compare athletes from various sports on snatch and vertical jump at 50, 80, and 90% 1-RM, demonstrating that generally as load increased maximal propulsion force decreased (177). Cormie et al. demonstrated that bodyweight resulted in larger peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> output when compared to an external load of 20, 40, 60, or 80% of 1-RM. Further, the shape of the force-, power-, and velocity-time curves were altered significantly when an external load was added, including a decrease in the rate of force development (RFD), especially early in the force/velocity curve (178). Gehri et al. compared 12 weeks of training with either counter-movement jump (CMJ) or depth jumps, demonstrating depth jumps resulted in larger improvements in jump height. Interestingly, the improvements were not due to increases in elastic energy (179). An older study by Berger et al. compared 7 weeks of training with isometric squats, 10-RM dynamic squats, 10 reps of loaded jump squats (50 - 60% of 1-RM), or CMJ, demonstrating that the loaded squat and loaded jump squat groups improved vertical jump height more than isometric squats or CMJ (180). Driss et al. computed instantaneous <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> from time-force curves during vertical jumps with and without an external load (0, 5, or 10 kg worn in a special vest). The jumps were performed from a squat position, without lower limb counter-movement or an arm swing. Instantaneous peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> was greatest with no external load in untrained individuals, but increased load increased instantaneous peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> in trained individuals until a load was reached that slowed peak velocity enough to decrease peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> output (181). These studies seem to imply that bodyweight training is likely <a id="superior" data-tip="1570" target="_blank" href="/glossary-term/superior" class="glossary">superior</a> for improving <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> for novice individuals; however, trained individuals may benefit from additional intensity by either adding height to a depth jump or adding external load no to exceed 30% of 1-RM
<h3>Peak Power:</h3>
Studies have compared a variety of loads in an attempt to determine the ideal load for improving <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> output. The findings of a study by Wilson et al. likely do the best job of summarizing best-practice for determining the <a id="optimal" data-tip="1571" target="_blank" href="/glossary-term/optimal" class="glossary">optimal</a> load. Wilson et al. compared 5 weeks of traditional weight training (squats), <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> training (depth jumps), and explosive weight training (loaded jump squats) with the load for each optimized for peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> output. The study determined that the training program that best-optimized <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> output resulted in the largest improvements on most tests; including 30m sprint, vertical jump, maximal cycle <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a>, isokinetic leg extension, and maximal isometric strength (182). Further studies reinforce the notion of load optimized for maximal <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> output, and trend toward the addition of some but not excessive external load. Lyttle et al. compared 8 weeks (2x/week) of loaded jump squats and bench press throws (loaded to maximize <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> output), to <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercises including depth jumps and medicine ball throws, demonstrating that both groups improved equally on a variety of performance measures including jumping, cycling, throwing, and lifting (184). Mcbride et al. investigated velocity-specific adaptations, comparing jump squat training with 30% of 1-RM and 80% 1-RM, demonstrating the 30% of 1-RM group performed better on a 20m sprint <a id="assessment" data-tip="1482" target="_blank" href="/glossary-term/assessment" class="glossary">test</a> (10). Childers et al. demonstrated that maximal peak and average <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> output during a hang clean occurred at 70% of 1RM; however, the differences were not significant between 50, 60, 80, and 90% 1-RM (185). Bevan et al. demonstrated that 0% of 1-RM for squat jumps and 30% of 1-RM for bench press throws resulted in the largest peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> output when compared to 20, 30, 40, 50, and 60% of 1-RM in a group of 47 professional, male, rugby players (186). These studies add to the conclusion of the previous paragraph, noting that external load can augment gains if the load does not reduce velocity enough to reduce peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>.

A few studies have compared different training volumes and their effect on <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> performance. A study by Ramirez-Campillo et al. compared different surfaces and volumes during 7 weeks of <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> training, noting that hard surfaces resulted in training adaptations at moderate volumes (110 jumps/week), whereas the high volumes (200+ jump/week) on softer surfaces groups exhibited the largest increases on various strength, jump and sprint tests (188). Note, there was not a high volume on hard surfaces group included in the study. Although this study suggests that an increase in volume leads to larger improvements in <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, additional studies suggest that intensity is a more important consideration, and intensity and volume likely have an inverse relationship. A study by Mangine et al. demonstrated that 8 weeks of training with high intensity and lower volume (3&#x2013;5 RM, 3-min rest interval) resulted in larger increases in RFD, than training with a high volume and lower intensity (10&#x2013;12 RM, 1-min rest interval) (189). Methenitis et al. compared training volumes of 3, 6, or 9 sets/session of super-sets that included 4 reps of fast-velocity eccentric half squats followed by 3 repetitions of maximum CMJ over 10 weeks. The largest increases in CMJ height and early RFD were exhibited by the 3-set group; further, a shift from IIx to IIa fiber proportion and loss of IIx CSA was noted in the 6 and 9 set groups, but not in the 3-set group (75). The loss of type IIx fibers may be an important consideration for any professional tempted to prioritize volume over intensity. R&#xF8;nnestad et al. compared 6-8 soccer sessions per week with the addition of either 7 weeks of strength training or strength training and <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> training, demonstrating that the addition of <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> activity during training did not result in any additional benefits in a variety of strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> tasks (170). In a follow-up study, R&#xF8;nnestad et al. compared 1 strength maintenance session/week, to 1 session every other week, demonstrating that 1 session/week successfully maintained the strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> gained during an off-season training program, while the every other week group saw a reduction in strength and 40m sprint performance time (190). These studies suggest that volume is secondary to intensity, and while sufficient volume is necessary to ensure adaptation, increasing volume (more than 3 - 5 sets) may not result in additional benefits. Further, training adaptations may be maintained with 1 session per week.
<table>
 <tbody>
 <tr>
 <td>
 Repetition Range (Velocity Dependent):
 Strangely, there seems to be no research comparing training with various repetition ranges of high velocity exercise (ballistic/power). Based on the studies above it may be reasonable to suggest that intensity/load is dependent on the ability to achieve the fastest possible velocity, and further, that reps should be limited to the number that can be performed at the fastest possible velocity. That is, a set should continue as long as velocity can be maintained, and stopped when velocity decreases; likely several reps before the athlete feels fatigued or reaches volitional failure. Based on the rep ranges most commonly used in the various studies above, a general guideline of 3-10 reps/set is likely reasonable. In summary, there is currently no research comparing rep ranges for high velocity activities, but based on the most commonly used rep ranges in <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training studies, 3-10 reps/set is likely a reasonable recommendation. A more <a id="specificity" data-tip="1224" target="_blank" href="/glossary-term/specificity" class="glossary">specific</a> recommendation would be to limit repetitions to the number of reps that can be performed at maximum velocity.
 </td>
 </tr>
 </tbody>
</table>

Olympic lifts are often recommended to athletes for <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> development, but the research does not <a id="base-of-support" data-tip="1197" target="_blank" href="/glossary-term/base-of-support" class="glossary">support</a> this recommendation. A randomized control <a id="randomized-control-trial" data-tip="1407" target="_blank" href="/glossary-term/randomized-control-trial" class="glossary">trial</a> (RCT) by Helland et al. compared the performance of 39 athletes (ice hockey, volleyball, and badminton), randomized into three training groups, performing 8 weeks (2-3x/week) of either Olympic lifting (clean and snatch), 2-leg and 1-leg squats using free weights, or 2-leg and 1-leg squats using an isotonic <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training machine with an augmented eccentric load. The results demonstrate that the Olympic lifting group exhibited less improvement on all tests, including CMJ, squat jump (SJ), drop jump (DJ), loaded CMJ (10&#x2013;80 kg), and 30-m sprint time. Both the free weight and machine training groups exhibited significant improvements on all tests, with the isotonic <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training machine resulting in the largest improvements on some tests (174). One factor contributing to the reduction in improvements may be related to &quot;follow through.&quot; Newton et al. demonstrated that during the concentric phase of a bench press throw with 45% 1-RM, average EMG was higher for <a href="https://brookbushinstitute.com/courses/pectoralis-major" target="_blank" rel="noopener">pectoralis major</a>, <a href="https://brookbushinstitute.com/courses/deltoids" target="_blank" rel="noopener">anterior deltoid</a>, triceps brachii, and biceps brachii, when compared to conventional bench press done with the quickest possible concentric contraction at all loads (202). Consider how this study compares to a study by Cronin. et al., which determined that load lifted during a clean was most correlated with greater peak accelerations (38.5% - mean across loads), greater initial force and peak forces (14.1% - mean across loads), and early termination of the concentric phase (203). These studies demonstrate that Olympic lifts are likely less effective than other forms of training for improving <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> performance for most athletes, perhaps due to the deceleration at the &quot;top&quot; of the movement. Based on the conceptual framework for improving <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> implied by the body of research, and observations of athletic team training, other factors that are likely to contribute to the reduced effectiveness of Olympic lifts include loads too heavy to achieve maximal velocity, low transference due to kinematics that do not match the force/velocity curve for most sporting activity (e.g. sprinting/jumping), the amount of time it takes to learn these techniques due to the complexity of the movement, and the relatively high potential for injury. Additional research investigating these factors, as well as additional comparative studies including various Olympic lifts and commonly used <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercises, are recommended. Note, training for individuals competing in sports that require Olympic lifting should include Olympic lifts, as this is the goal of the athlete.
<img title="An example of the snatch exercise used in olympic weighlifting" src="https://www.datocms-assets.com/25800/1649512190-olympic-lift.jpg" alt="An olympic lift often used for increasing power">

Power Training Progressions

<h4>Lower Body</h4>
Several studies have evaluated and ranked <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training exercises based on a variety of factors, aiding in the development of <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercise <a id="exercise-progression" data-tip="1182" target="_blank" href="/glossary-term/exercise-progression" class="glossary">progressions</a>. Jensen et al. compared the <a id="ground-reaction-force" data-tip="1397" target="_blank" href="/glossary-term/ground-reaction-force" class="glossary">ground reaction forces</a> (<a id="ground-reaction-force" data-tip="1398" target="_blank" href="/glossary-term/ground-reaction-force" class="glossary">GRF</a>) during the landing of several lower body <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> exercises, demonstrating that cone hops and single-leg jumps resulted in lower <a id="ground-reaction-force" data-tip="1398" target="_blank" href="/glossary-term/ground-reaction-force" class="glossary">GRF</a> forces than depth jumps (60 cm) and tuck jumps (191). Another similar study by Jensen et al. compared lower body <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training exercises by the rate of force development (RFD), knee joint reaction forces, and <a id="ground-reaction-force" data-tip="1398" target="_blank" href="/glossary-term/ground-reaction-force" class="glossary">GRF</a>, resulting in a similar ranking of lower body exercises; however, in this study differences did not achieve statistical significance (192). A study by Ebben et al. compared perceived intensity and quantified kinetics of various <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> exercises, demonstrating that RFD and <a id="ground-reaction-force" data-tip="1398" target="_blank" href="/glossary-term/ground-reaction-force" class="glossary">GRF</a> time had a larger influence on perceived intensity than jump height (193). These studies likely imply that overcoming additional eccentric load to achieve a ballistic goal, has a larger influence on lower body <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercise intensity than jump height.
Additional studies have investigated the influence of <a id="stability" data-tip="1191" target="_blank" href="/glossary-term/stability" class="glossary">stability</a> on <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> training. Another study by Ebben et al. demonstrated that <a id="base-of-support" data-tip="1195" target="_blank" href="/glossary-term/base-of-support" class="glossary">base of support</a> and jump height were key factors in determining the <a id="exercise-progression" data-tip="1184" target="_blank" href="/glossary-term/exercise-progression" class="glossary">progression</a> of <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> exercises based on time to stabilization (<a id="stability" data-tip="1191" target="_blank" href="/glossary-term/stability" class="glossary">stability</a>). Exercises such as the cone hop resulted in the shortest time to stabilization, whereas the tuck jump and single-leg jump exercises resulted in the longest time to stabilization (194). Myer et al. compared female athletes following 7 weeks (3x/week) of <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> training or dynamic stabilization programs, demonstrating that <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> training had a larger effect on landing force; however, both programs improved <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>, strength, and symmetry during landing (195). And, Bodganis et al. compared the outcomes of single-leg and double-leg <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> training on single-leg and double-leg jump performance, demonstrating single-leg <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> training was more effective at increasing both single-leg and double-leg jumping performance, isometric leg press maximal strength, and RFD (196). Based on these studies, perhaps more consideration should be given to <a id="stability" data-tip="1191" target="_blank" href="/glossary-term/stability" class="glossary">stability</a> as a factor in <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercise intensity, and <a id="stability-training" data-tip="1172" target="_blank" href="/glossary-term/stability-training" class="glossary">stability training</a> considered in training programs with the intent to increase an athlete&apos;s <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>.
The following <a id="exercise-progression" data-tip="1184" target="_blank" href="/glossary-term/exercise-progression" class="glossary">progression</a> combined the various rank orders demonstrated in these studies, to create a &quot;general progression&quot;. Several exercises that are not commonly used by the Brookbush Institute were omitted to aid in simplifying the <a id="exercise-progression" data-tip="1184" target="_blank" href="/glossary-term/exercise-progression" class="glossary">progression</a> below. It is recommended that you refer to the individual studies cited above if you believe one of the studied variables is more important for a particular case or group of athletes.
<h4>Progression based on GRF, RFD, joint power absorption, and time to stabilization:</h4>
<ol>
 <li>Counter Movement Jump</li>
 <li>Box Jump</li>
 <li>Cone hop</li>
 <li>Single leg jump</li>
 <li>Depth jump</li>
 <li>Tuck jump</li>
</ol>
<ul>
 <li>Note: Subtle differences do appear in the <a id="exercise-progression" data-tip="1182" target="_blank" href="/glossary-term/exercise-progression" class="glossary">progressions</a> implied by the studies above; for example, single-leg jump has the lowest RFD, highest time to stabilization, but falls in the middle relative to <a id="ground-reaction-force" data-tip="1398" target="_blank" href="/glossary-term/ground-reaction-force" class="glossary">GRF</a> and joint <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> absorption.</li>
</ul>
<h4>Progression based on EMG Activity:</h4>
A study by Ebben et al. resulted in a potentially counter-intuitive finding, demonstrating that higher loads during lower body <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercises resulted in lower <a id="motor-unit" data-tip="1303" target="_blank" href="/glossary-term/motor-unit" class="glossary">motor unit</a> recruitment. That is, cone hops, box jumps and tuck jumps resulted in more <a id="motor-unit" data-tip="1303" target="_blank" href="/glossary-term/motor-unit" class="glossary">motor unit</a> recruitment than single-leg jumps and depth jumps (197). This may be due to the slower RFD, or perhaps an increased reliance on the elastic potential of <a id="connective-tissue-cell" data-tip="1368" target="_blank" href="/glossary-term/connective-tissue-cell" class="glossary">connective tissue</a> during the lower load/higher velocity exercise.
<ol>
 <li>Depth jump 61cm</li>
 <li>Depth jump 30.48cm</li>
 <li>Single-leg vertical jump and reach</li>
 <li>Box jump 61cm</li>
 <li>Tuck jump (and Cone Hop)</li>
 <li>Double leg vertical jump and reach</li>
</ol>
<h4>Intensity by Joint Power Absorption</h4>
A study by Van Lieshout et al. compared several lower body <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercises relative to peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> absorption by joint, demonstrating significant differences (198). Although the <a id="exercise-progression" data-tip="1182" target="_blank" href="/glossary-term/exercise-progression" class="glossary">progressions</a> are similar to the &quot;general progression&quot; above, the subtle differences may have implications for progressing rehab programs following an injury of a particular joint.
<table>
 <tbody>
 <tr>
 <td colspan="4">Van Lieshout et al. (198) Intensity by Joint Power Absorption (low to high)</td>
 </tr>
 <tr>
 <td>Sum Peak Power</td>
 <td>Ankle Joint Peak Power</td>
 <td>Knee Joint Peak Power</td>
 <td>Hip Joint Peak Power</td>
 </tr>
 <tr>
 <td>
 <ol>
 <li>Box jump up</li>
 <li>Box drop</li>
 <li>Backward Jump</li>
 <li>Vertical Jump</li>
 <li>Depth Jump</li>
 <li>Forward Jump</li>
 <li>Tuck Jump</li>
 </ol>
 </td>
 <td>
 <ol>
 <li>Box drop</li>
 <li>Box jump up</li>
 <li>Backward jump</li>
 <li>Depth jump</li>
 <li>Vertical jump</li>
 <li>Forward jump</li>
 <li>Tuck jump</li>
 </ol>
 </td>
 <td>
 <ol>
 <li>Backward jump</li>
 <li>Box jump up</li>
 <li>Box drop</li>
 <li>Vertical jump</li>
 <li>Tuck jump</li>
 <li>Depth jump</li>
 <li>Forward jump</li>
 </ol>
 </td>
 <td>
 <ol>
 <li>Box jump up</li>
 <li>Box drop</li>
 <li>Forward jump</li>
 <li>Backward jump</li>
 <li>Vertical jump</li>
 <li>Depth jump</li>
 <li>Tuck jump</li>
 </ol>
 </td>
 </tr>
 </tbody>
</table>

Upper Body
Only two studies were located ranking upper-body <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> exercises. Koch et al. demonstrated that force increased during <a id="plyometric" data-tip="1295" target="_blank" href="/glossary-term/plyometric" class="glossary">plyometric</a> push-ups as box drop height increased from 4 - 12cm; however, clapping push-ups resulted in the highest loads and propulsion rates (199). Ignjatovic et al. compared eight weeks of bench press and squat training on stable and <a id="stability" data-tip="1194" target="_blank" href="/glossary-term/stability" class="glossary">unstable</a> surfaces, demonstrated the largest increases in peak <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> were exhibited by the <a id="stability" data-tip="1194" target="_blank" href="/glossary-term/stability" class="glossary">unstable</a> surface group (recreationally active subjects) (200). These studies may imply the following <a id="exercise-progression" data-tip="1184" target="_blank" href="/glossary-term/exercise-progression" class="glossary">progression</a> for <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a> push-ups.
<ol>
 <li>4 - 12 cm Box Drop Push-Up</li>
 <li>Clap Push-Up</li>
 <li><a id="stability" data-tip="1194" target="_blank" href="/glossary-term/stability" class="glossary">Unstable</a> Environments</li>
</ol>
<h3>Additional Factors</h3>
A handful of additional studies highlight key factors that should be the focus of additional research. Behm et al. compared the training response following 16 weeks (3 days/week) of <a href="https://brookbushinstitute.com/courses/tibialis-anterior" target="_blank" rel="noopener">tibialis anterior</a> high-velocity contractions against an isokinetic dynamometer (isometric contractions) to high-velocity contractions without resistance on the other leg. An increase in RFD was demonstrated on both sides, suggesting that the principal stimuli for adaptation to high-velocity training may be the intent to perform high-velocity repetitions, and not necessarily <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> action through a range of motion (201). As mentioned above, Newton et al. demonstrated that during the concentric phase of a bench press with 45% 1-RM, average EMG was higher for <a href="https://brookbushinstitute.com/courses/pectoralis-major" target="_blank" rel="noopener">pectoralis major</a>, <a href="https://brookbushinstitute.com/courses/deltoids" target="_blank" rel="noopener">anterior deltoid</a>, triceps brachii, and biceps brachii, when compared to traditional bench press at all loads done explosively; likely demonstrating the importance of follow-through (202). Consider how this study compares to a study by Cronin. et al., which determined that load lifted during a clean was most correlated with greater peak accelerations (38.5% - mean across loads), greater initial force and peak forces (14.1% - mean across loads), and early termination of the concentric phase (203). In consideration of the Newton et al. study (202), the early termination of the concentric phase during a clean may suggest that this type of training is not ideal for optimizing <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">power</a>. In another interesting study, Schilling et al. demonstrated that there was no correlation between foot motion, placement (forward, neutral, back, asymmetrical), and lifting performance during the 1998 U.S.A. Weightlifting Collegiate National Championships (204). This study likely implies that trainers should focus on <a id="optimal" data-tip="1571" target="_blank" href="/glossary-term/optimal" class="glossary">optimal</a> alignment and <a id="posture" data-tip="1660" target="_blank" href="/glossary-term/posture" class="glossary">form</a> based on the absence of signs correlated with dysfunction (e.g. no knee valgus), rather than attempting to replicate the <a id="posture" data-tip="1660" target="_blank" href="/glossary-term/posture" class="glossary">form</a> demonstrated by a competitive lifter. In summary, the additional factors of intent to generate ballistic force and follow-through (letting go, leaving the ground, etc) may provide additional benefits, while focusing on foot placement or motion is likely to result in little if any benefit.

<h3>Practical Application:</h3>
Strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">Power</a> Training: The combination of strength and <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">Power</a> training is likely more beneficial than either strength or <a id="power" data-tip="1399" target="_blank" href="/glossary-term/power" class="glossary">Power</a> training alone.
Acute Variables for Ballistic Training:
<ul>
 <li>Intensity: As much load as can be moved with maximal velocity</li>
 <li>Volume: 3 - 5 sets</li>
 <li>Repetitions: 3 - 10 (reps the number of repetitions that can be performed at maximum velocity)</li>
 <li>Additional Factors: Ballistic intent and follow-through</li>
 <li>Exercise Progression: (General <a id="evidence-based-practice" data-tip="1538" target="_blank" href="/glossary-term/evidence-based-practice" class="glossary">evidence-based</a> exercise <a id="exercise-progression" data-tip="1182" target="_blank" href="/glossary-term/exercise-progression" class="glossary">progressions</a>)
 <ul>
 <li>Upper Body
 <ul>
 <li>4 - 12 cm Box Drop Push-Up</li>
 <li>Clap Push-Up</li>
 <li>Unstable Environments</li>
 </ul>
 </li>
 <li>Lower Body
 <ol>
 <li>Counter Movement Jump</li>
 <li>Box Jump</li>
 <li>Cone hop</li>
 <li>Single leg jump</li>
 <li>Depth jump</li>
 <li>Tuck jump</li>
 </ol>
 </li>
 </ul>
 </li>
</ul>

Bibliography

© Brent Brookbush 2020
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.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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