Introduction

More on Function

Signs of Deep Longitudinal Dysfunction

Deep Laminae of the Posterior Layer (DL) of the Thoracolumbar Fascia (TLF):

Sacrotuberous Ligament

Erector Spinae

Biceps Femoris, Piriformis, Deep Rotators, and Adductor Magnus

Fibularis (Peroneal) Muscles

Rhomboids

Splenius Capitis and Splenius Cervicis (Splenii)

Summary of Research Findings

Deep Longitudinal Subsystem (DLS)

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Deep Longitudinal Subsystem

This course describes the deep longitudinal subsystem (DLS). The deep longitudinal subsystem may also be referred to as the deep longitudinal sling, deep longitudinal system, deep <a id="posterior" data-tip="1565" target="_blank" href="/glossary-term/posterior" class="glossary">posterior</a> subsystem, deep <a id="posterior" data-tip="1565" target="_blank" href="/glossary-term/posterior" class="glossary">posterior</a> sling, deep <a id="posterior" data-tip="1565" target="_blank" href="/glossary-term/posterior" class="glossary">posterior</a> myofascial synergy, and is similar to the concepts of body slings, <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> synergies, myofascial lines, myofascial trains, anatomy trains, superficial back line, spiral line, and the serape effect. This course covers a detailed analysis of the <a id="posterior" data-tip="1565" target="_blank" href="/glossary-term/posterior" class="glossary">posterior</a> oblique subsystem (sling) including anatomy, research, <a id="integration" data-tip="1472" target="_blank" href="/glossary-term/integration" class="glossary">integration</a> techniques and a sample routine.
<h4>The Deep Longitudinal Subsystem (DLS) is comprised of:</h4>
<ul>
 <li>Thoracolumbar Fascia (Deep <a id="posterior" data-tip="1565" target="_blank" href="/glossary-term/posterior" class="glossary">Posterior</a> layer)</li>
 <li><a href="https://brookbushinstitute.com/courses/erector-spinae">Erector Spinae</a></li>
 <li><a href="https://brookbushinstitute.com/courses/rhomboids">Rhomboids</a></li>
 <li>Splenius Capitis and Splenius Cervicis</li>
 <li>Sacrotuberous Ligament</li>
 <li><a href="https://brookbushinstitute.com/courses/biceps-femoris">Biceps Femoris</a></li>
 <li><a href="https://brookbushinstitute.com/courses/adductors">Adductor magnus</a></li>
 <li>Piriformis</li>
 <li>Obturator internus (and deep hip external rotators)</li>
 <li>Head of Fibula</li>
 <li>Fibularis Longus</li>
</ul>
The concepts and techniques described in this course may be particularly beneficial for neuromuscular re-education, coordination, motor pattern <a id="integration" data-tip="1472" target="_blank" href="/glossary-term/integration" class="glossary">integration</a>, whole-body strength, functional strength, and sports performance. Sports medicine professionals (personal trainers, fitness instructors, physical therapists, massage therapists, chiropractors, occupational therapists, athletic trainers, etc.) should consider adding these exercises to their repertoire to improve the outcomes of their <a id="integration" data-tip="1473" target="_blank" href="/glossary-term/integration" class="glossary">integrated</a> exercise programs, sports performance programs, and therapeutic (rehabilitation) interventions.
<h4>For additional self-administered joint mobilization techniques check out:</h4>
<ul>
 <li><a href="https://brookbushinstitute.com/courses/intrinsic-stabilization-subsystem">Intrinsic Stabilization Subsystem (ISS)</a></li>
 <li><a href="https://brookbushinstitute.com/courses/anterior-oblique-subsystem-aos">Anterior Oblique Subsystem (AOS)</a></li>
 <li><a href="https://brookbushinstitute.com/courses/posterior-oblique-subsystem-pos">Posterior Oblique Subsystem (POS)</a></li>
</ul>

Course Description: Deep Longitudinal Subsystem

<h4><a href="https://www.datocms-assets.com/25800/1684182797-deep-longitudinal-subsystem-study-guide-pdf.pdf" title="Quick Study Guide: Deep Longitudinal Subsystem (DLS)" target="_blank" rel="noopener">Quick Study Guide: Deep Longitudinal Subsystem (DLS)</a></h4>
<h4>Function (Brief):</h4>
The DLS is comprised of muscles with a propensity to act synergistically; rarely do these muscles act as <a id="prime-mover" data-tip="1663" target="_blank" href="/glossary-term/prime-mover" class="glossary">prime movers</a>. This subsystem plays an important role in the motion of the <a href="https://brookbushinstitute.com/courses/ankle-joint-talocrural-subtalor-tibiofibular-joints" target="_blank" rel="noopener">tibiofibular joints</a>, <a href="https://brookbushinstitute.com/courses/hip-joint" target="_blank" rel="noopener"> hip joints</a>, sacroiliac joints, and spine, and may aid in proprioception by altering recruitment strategies based on the load and stretch imparted on the system during heel strike. The DLS is active during gait, forward bending (more so when knees are near full extension), and lumbar extension, and eccentrically decelerates spine flexion, <a href="https://brookbushinstitute.com/courses/hip-joint" target="_blank" rel="noopener"> hip</a> flexion, and <a href="https://brookbushinstitute.com/courses/ankle-joint-talocrural-subtalor-tibiofibular-joints" target="_blank" rel="noopener">ankle</a> inversion. Over-activity of the DLS is often accompanied by relative inhibition of the <a href="https://brookbushinstitute.com/courses/posterior-oblique-subsystem-pos" target="_blank" rel="noopener"> </a><a id="posterior" data-tip="1565" target="_blank" href="/glossary-term/posterior" class="glossary">Posterior</a> Oblique Subsystem (POS).
<h3><img src="https://www.datocms-assets.com/25800/1650602359-dls-2.png" title="Picture of the muscles in the deep longitudinal subsystem" alt="The deep longitudinal subsystem"></h3>
<ul>
 <li> Concentric Function: Assists with propulsion from heel strike to push-off during gait, assists with lifting from a forward bent position, and lumbar hyper-extension</li>
 <li> Isometric Function: Stabilization of tibiofibular joints, hip joints, sacroiliac joints, and all segments of the spine.</li>
 <li> Eccentric Function: Decelerates leg swing and impact during heel strike, eccentrically decelerates forward bending, and eccentrically decelerates ankle inversion.</li>
</ul>
<h3> Common Maladaptive Behavior </h3>
<ul>
 <li>Over-active</li>
</ul>

<ul>
 <li> <a href="https://brookbushinstitute.com/courses/solutions-table-overhead-squat-assessment" target="_blank" rel="noopener"> Overhead Squat </a><a id="assessment" data-tip="1478" target="_blank" href="/glossary-term/assessment" class="glossary">Assessment</a> 
 <ul>
 <li><a href="https://brookbushinstitute.com/video/overhead-squat-assessment-11-shoulders-elevate" target="_blank" rel="noopener"> Shoulders elevate </a></li>
 <li><a href="https://brookbushinstitute.com/video/overhead-squat-assessment-9-anterior-pelvic-tilt-excessive-lordosis" target="_blank" rel="noopener"> </a><a id="anterior" data-tip="1566" target="_blank" href="/glossary-term/anterior" class="glossary">Anterior</a> pelvic tilt </li>
 <li><a href="https://brookbushinstitute.com/video/overhead-squat-assessment-15-sign-clusters-asymmetrical-weight-shift" target="_blank" rel="noopener"> Asymmetrical weight shift </a></li>
 <li><a href="https://brookbushinstitute.com/video/overhead-squat-assessment-6-knees-bow-in-breakdown" target="_blank" rel="noopener"> Knees bow in </a></li>
 <li><a href="https://brookbushinstitute.com/video/overhead-squat-assessment-7-knees-bow-out" target="_blank" rel="noopener"> Knees bow out </a></li>
 <li><a href="https://brookbushinstitute.com/video/overhead-squat-assessment-5-feet-turn-out-breakdown" target="_blank" rel="noopener"> Feet turn out </a></li>
 <li><a href="https://brookbushinstitute.com/video/overhead-squat-assessment-4-feet-flat-breakdown" target="_blank" rel="noopener"> Feet flatten</a></li>
 </ul>
 </li>
</ul>
<img title="Dr. Brent Brookbush demonstrating feet turn out during the overhead squat assessment" src="https://www.datocms-assets.com/25800/1649862955-feet-turn-out.jpg" width="287" height="380" alt="An example of feet turn out">
<h3> Practical Application </h3>
<ul>
 <li> <a id="release" data-tip="1249" target="_blank" href="/glossary-term/release" class="glossary">Release</a> (self-administered, vibration, or manual): 
 <ul>
 <li><a href="https://brookbushinstitute.com/courses/lumbar-extensor-flexibility"> Erector Spinae </a></li>
 <li><a href="https://brookbushinstitute.com/courses/scapular-muscle-flexibility" target="_blank" rel="noopener"> Rhomboids </a></li>
 <li><a href="https://brookbushinstitute.com/video/cervical-extensor-self-administered-static-release" target="_blank" rel="noopener"> Splenius Capitis and Splenius Cervicis </a></li>
 <li><a href="https://brookbushinstitute.com/courses/hip-external-rotator-flexibility"> Biceps Femoris </a></li>
 <li><a href="https://brookbushinstitute.com/courses/hip-external-rotator-flexibility"> Adductor magnus </a></li>
 <li><a href="https://brookbushinstitute.com/courses/hip-external-rotator-flexibility"> Piriformis, Obturator internus (and deep rotators) </a></li>
 <li><a href="https://brookbushinstitute.com/courses/lower-leg-flexibility"> Fibularis Longus </a></li>
 </ul>
 <a href="https://brookbushinstitute.com/courses/lower-leg-flexibility"> </a>
 </li>
 <li> Core 
 <ul>
 <li>Avoid exercises that focus on <a href="https://brookbushinstitute.com/courses/erector-spinae" target="_blank" rel="noopener">erector spinae</a>, <a href="https://brookbushinstitute.com/courses/adductors" target="_blank" rel="noopener"> adductor</a>, and/or <a href="https://brookbushinstitute.com/courses/biceps-femoris" target="_blank" rel="noopener">hamstring</a> strengthening.</li>
 </ul>
 </li>
 <li> <a href="https://brookbushinstitute.com/glossary/integration/" target="_blank" rel="noopener"> </a><a id="integration" data-tip="1473" target="_blank" href="/glossary-term/integration" class="glossary">Integrated</a> Exercise 
 <ul>
 <li>Avoid straight-legged <a href="https://brookbushinstitute.com/courses/deadlift-progression" target="_blank" rel="noopener">deadlifts</a> and kettlebell windmills.</li>
 </ul>
 </li>
</ul>

Signs of DLS Dysfunction 

<h3>Sample Routine (Knees bow out) </h3>
<ul>
 <li> <a id="mobility" data-tip="1455" target="_blank" href="/glossary-term/mobility" class="glossary">Mobility</a> 
 <ul>
 <li>Release
 <ul>
 <li><a href="https://brookbushinstitute.com/video/biceps-femoris-sa-static-release" target="_blank" rel="noopener"> Biceps Femoris </a><a id="release" data-tip="1249" target="_blank" href="/glossary-term/release" class="glossary">Release</a> </li>
 <li><a href="https://brookbushinstitute.com/video/piriformis-sa-static-release" target="_blank" rel="noopener"> Piriformis </a><a id="release" data-tip="1249" target="_blank" href="/glossary-term/release" class="glossary">Release</a> </li>
 <li><a href="https://brookbushinstitute.com/video/adductor-magnus-posterior-sa-static-release" target="_blank" rel="noopener"> Adductor Magnus </a><a id="release" data-tip="1249" target="_blank" href="/glossary-term/release" class="glossary">Release</a> </li>
 <li><a href="https://brookbushinstitute.com/video/gastroc-and-soleus-calf-sa-static-release" target="_blank" rel="noopener"> Calf </a><a id="release" data-tip="1249" target="_blank" href="/glossary-term/release" class="glossary">Release</a> </li>
 </ul>
 </li>
 <li>Mobilization
 <ul>
 <li><a href="https://brookbushinstitute.com/video/open-books-self-administered-spine-rotational-mobilizations" target="_blank" rel="noopener"> Open Books </a></li>
 </ul>
 </li>
 <li>Lengthen
 <ul>
 <li><a href="https://brookbushinstitute.com/video/latissimus-dorsi-and-erector-spinae-static-stretch-childs-pose" target="_blank" rel="noopener"> Childs Pose (Erector Spinae) </a></li>
 <li><a href="https://brookbushinstitute.com/video/biceps-femoris-active-stretch" target="_blank" rel="noopener"> Biceps Femoris Active Stretch </a></li>
 <li><a href="https://brookbushinstitute.com/video/slant-board-calf-stretch" target="_blank" rel="noopener"> Slant board calf stretch </a></li>
 </ul>
 </li>
 </ul>
 </li>
 <li> Activity 
 <ul>
 <li>Isolated Activation
 <ul>
 <li><a href="https://brookbushinstitute.com/video/quick-glute-activation-circuit" target="_blank" rel="noopener"> Glute activation circuit </a></li>
 <li><a href="https://brookbushinstitute.com/video/tibialis-anterior-isolated-activation" target="_blank" rel="noopener"> Tibialis </a><a id="anterior" data-tip="1566" target="_blank" href="/glossary-term/anterior" class="glossary">anterior</a> activation (no equipment) </li>
 <li><a href="https://brookbushinstitute.com/video/vmo-activation-progressions" target="_blank" rel="noopener"> Terminal knee extension </a></li>
 </ul>
 </li>
 <li> Core <a id="integration" data-tip="1472" target="_blank" href="/glossary-term/integration" class="glossary">Integration</a> 
 <ul>
 <li><a href="https://brookbushinstitute.com/video/ultimate-glute-bridge" target="_blank" rel="noopener"> Ultimate Glute Bridge </a></li>
 </ul>
 </li>
 <li> Subsystem <a id="integration" data-tip="1472" target="_blank" href="/glossary-term/integration" class="glossary">Integration</a> 
 <ul>
 <li><a href="https://brookbushinstitute.com/video/step-up-to-row" target="_blank" rel="noopener"> Step-up to Row</a></li>
 </ul>
 </li>
 </ul>
 </li>
</ul>

Sample Routine

The communicating fascial structures of the DLS are the deep laminae of the posterior layer (DL) of the thoracolumbar fascia (TLF), the sacrotuberous ligament, and the fascial continuity between the biceps femoris and fibularis muscles at the fibular head.

Research Corner

The anatomy of the DL is the fascial link between the upper body muscles of the Deep Longitudinal Subsystem (DLS). The DL runs from the splenius capitis and splenius cervicis, to the superficial fascia of the <a href="https://brookbushinstitute.com/courses/rhomboids" target="_blank" rel="noopener">rhomboids</a>, enveloping the <a href="https://brookbushinstitute.com/courses/erector-spinae" target="_blank" rel="noopener">erector spinae </a> (investing in and reinforcing the paraspinal retinacular sheath), and is continuous with the sacrotuberous ligament (2-4). This implies that the DL has fascial continuity with structures from the hip to the skull. Further, the DL and the middle layer of the TLF fuse to <a id="posture" data-tip="1660" target="_blank" href="/glossary-term/posture" class="glossary">form</a> the <a href="https://brookbushinstitute.com/glossary/lateral/" target="_blank" rel="noopener">lateral </a>raphe. Note, the middle layer of the TLF is a fusion of the fascia of the <a href="https://brookbushinstitute.com/courses/anterior-oblique-subsystem-aos" target="_blank" rel="noopener"> </a><a id="anterior" data-tip="1566" target="_blank" href="/glossary-term/anterior" class="glossary">Anterior</a> Oblique Subsystem (AOS), and the deep fascia of the <a href="https://brookbushinstitute.com/courses/latissimus-dorsi" target="_blank" rel="noopener">latissimus dorsi</a> of the <a href="https://brookbushinstitute.com/courses/posterior-oblique-subsystem-pos" target="_blank" rel="noopener">Posterior Oblique Subsystem (POS) </a>(5). This both thickens the middle layer of the TLF to reinforce muscular attachments, and it may serve to ingrate the DLS, <a href="https://brookbushinstitute.com/courses/anterior-oblique-subsystem-aos" target="_blank" rel="noopener">AOS</a>, and <a href="https://brookbushinstitute.com/courses/posterior-oblique-subsystem-pos" target="_blank" rel="noopener">POS </a> (2, 4). The idea of <a href="https://brookbushinstitute.com/courses/posterior-oblique-subsystem-pos" target="_blank" rel="noopener">POS </a>and DLS <a id="integration" data-tip="1472" target="_blank" href="/glossary-term/integration" class="glossary">integration</a> is reinforced by a study by Kim et al. demonstrating synergistic <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> activity during gait (8), and DLS and <a href="https://brookbushinstitute.com/courses/anterior-oblique-subsystem-aos" target="_blank" rel="noopener">AOS </a> <a id="integration" data-tip="1472" target="_blank" href="/glossary-term/integration" class="glossary">integration</a> is reinforced by a study by Stevens et al. which demonstrated the co-contraction of various muscles investing in the DL and middle layers of the TLF during a &#x201C;<a href="https://brookbushinstitute.com/video/transverse-abdominis-tva-isolated-activation-quadruped" target="_blank" rel="noopener">quadruped</a>&#x201D; exercise (9). The similar behavior of all muscles that invest in the DL may have been what inspired this myofascial synergy, and the interaction between the layers of the TLF inspires consideration of core subsystem <a id="integration" data-tip="1472" target="_blank" href="/glossary-term/integration" class="glossary">integration</a>.
The DL may also serve an important mechanical function by enveloping and reinforcing the paraspinal retinaculum; a sheath of fascial tissue wrapping the <a href="https://brookbushinstitute.com/courses/erector-spinae" target="_blank" rel="noopener">erector spinae</a> horizontally, from the tip of the spinous processes to the tip of transverse processes (6, 10). Schuenke et al. demonstrated that inflation of the retinaculum by extensor muscles altered the moment arm and load angle of muscles investing in the superficial <a id="posterior" data-tip="1565" target="_blank" href="/glossary-term/posterior" class="glossary">posterior</a> layer and middle layer of the TLF (6). This may imply that <a id="optimal" data-tip="1571" target="_blank" href="/glossary-term/optimal" class="glossary">optimal</a> function of the abdominal tourniquet muscles, the <a href="https://brookbushinstitute.com/courses/intrinsic-stabilization-subsystem" target="_blank" rel="noopener">Intrinsic Stabilization Subsystem</a>&#xA0;and <a href="https://brookbushinstitute.com/courses/anterior-oblique-subsystem-aos" target="_blank" rel="noopener">AOS,</a> are dependent on inflation of the extensor retinaculum; and therefore, <a id="optimal" data-tip="1571" target="_blank" href="/glossary-term/optimal" class="glossary">optimal</a> function of the DLS. Further, Huskins et al. proposed that reinforcement of the extensor retinaculum may increase force output of the <a href="https://brookbushinstitute.com/courses/erector-spinae" target="_blank" rel="noopener">erector spinae</a> by up to 30% by restricting radial expansion (10). Last, inflation of the extensor retinaculum has been hypothesized to stiffen the DL aiding in eccentric deceleration of flexion forces (3, 4). This reinforcement of the extensor retinaculum by the DL may aid in <a id="optimal" data-tip="1571" target="_blank" href="/glossary-term/optimal" class="glossary">optimal</a> function and <a id="integration" data-tip="1472" target="_blank" href="/glossary-term/integration" class="glossary">integration</a> of subsystems, lumbar extensor force production, and stabilization of the lumbar spine.
Note: A study by Levangin et al. demonstrated a reduction in <a href="https://brookbushinstitute.com/glossary/glide/" target="_blank" rel="noopener">shear</a> strain between the <a id="posterior" data-tip="1565" target="_blank" href="/glossary-term/posterior" class="glossary">posterior</a> layers of the TLF (superficial and deep laminae) in those with a history of low back pain (11). Further, a study by De Coninck et al. demonstrated good inter-rater <a id="reliability" data-tip="1515" target="_blank" href="/glossary-term/reliability" class="glossary">reliability</a> for assessing disorganization of thoracolumbar fascia fibers via ultra-sound in those with low back pain (12). How this may affect the <a id="optimal" data-tip="1571" target="_blank" href="/glossary-term/optimal" class="glossary">optimal</a> recruitment of subsystems, in particular, the DLS and <a href="https://brookbushinstitute.com/courses/posterior-oblique-subsystem-pos" target="_blank" rel="noopener"> </a><a id="posterior" data-tip="1565" target="_blank" href="/glossary-term/posterior" class="glossary">posterior</a> Oblique Subsystem (POS) has yet to be researched, but it may be reasonable to consider potential alterations in practice. Research has shown that direct pressure to the thoracolumbar fascia will increase <a id="extensibility-2" data-tip="1308" target="_blank" href="/glossary-term/extensibility-2" class="glossary">extensibility</a>, either manually (13) or with a foam <a id="roll" data-tip="1602" target="_blank" href="/glossary-term/roll" class="glossary">roll</a> (14). However, stretching the TLF via a <a href="https://brookbushinstitute.com/video/latissimus-dorsi-and-erector-spinae-static-stretch-childs-pose" target="_blank" rel="noopener"> latissimus dorsi stretch</a> will not affect <a id="extensibility-2" data-tip="1308" target="_blank" href="/glossary-term/extensibility-2" class="glossary">extensibility</a> (15). This may imply that for addressing fascial dysfunction, direct manual pressure is effective, and stretching is not. Research is needed on &quot;fascial shear&quot; techniques like Instrument Assisted Soft Tissue Mobilization, Pin and Stretch, and Myofascial <a id="release" data-tip="1249" target="_blank" href="/glossary-term/release" class="glossary">Release</a>.
<a href="https://brookbush.s3.us-east-2.amazonaws.com/wordpress/wp-content/uploads/2012/02/Thoracolumbar-fascia.jpg" target="_blank" rel="noopener"><img src="https://www.datocms-assets.com/25800/1650602531-muscles-surrounding-the-spine.jpg" title="Layers of the thoracolumbar fascia with supporting muscles including the latissimus dorsi, erector spinae, psoas, and iliacus" alt="The layers of the thoracolumbar fascia and muscle of the spine"> </a>
Layers of Thoracolumbar Fascia and Lumbar Spine musculature.

The sacrotuberous ligament is a complex structure that plays a significant role in sacroiliac joint (SIJ) function and serves as an attachment site for several muscles. Research has demonstrated that the <a href="https://brookbushinstitute.com/courses/biceps-femoris" target="_blank" rel="noopener">biceps femoris</a> and <a href="https://brookbushinstitute.com/courses/gluteus-maximus" target="_blank" rel="noopener">gluteus maximus</a> may increase <a id="tension" data-tip="1229" target="_blank" href="/glossary-term/tension" class="glossary">tension</a> in the sacrotuberous ligament (16, 17, 105), further, the piriformis, semitendinosus, semimembranosus, obturator internus, and multifidus have been implicated by researchers due to their attachments (18), and the Brookbush Institute considers the ichiocondylar (<a id="posterior" data-tip="1565" target="_blank" href="/glossary-term/posterior" class="glossary">posterior</a>) head of the <a href="https://brookbushinstitute.com/courses/adductors" target="_blank" rel="noopener">adductor magnus</a> part of this group despite a void in the research (other than reference to its attachment in various anatomy textbooks). Studies by Vleeming et al. have shown that contraction of these muscles may increase <a id="tension" data-tip="1229" target="_blank" href="/glossary-term/tension" class="glossary">tension</a> of the sacrotuberous ligament, which may contribute to <a href="https://brookbushinstitute.com/glossary/force-closure/" target="_blank" rel="noopener">force closure</a> and stiffness of the sacroiliac joint (SIJ) (16, 19, 20, 105). Further, studies have demonstrated that increased <a id="tension" data-tip="1229" target="_blank" href="/glossary-term/tension" class="glossary">tension</a> of the sacrotuberous ligament via muscular contraction can resist <a id="nutation" data-tip="1213" target="_blank" href="/glossary-term/nutation" class="glossary">nutation</a> (17, 20). The contribution to <a id="force-closure" data-tip="1448" target="_blank" href="/glossary-term/force-closure" class="glossary">force closure</a>, stiffness, and resistance to <a id="nutation" data-tip="1213" target="_blank" href="/glossary-term/nutation" class="glossary">nutation</a> may imply important roles in both stabilization and dysfunction of the SIJ, specifically contributions to <a href="https://brookbushinstitute.com/courses/lumbo-pelvic-hip-complex-dysfunction-lphcd" target="_blank" rel="noopener">Lumbo Pelvic Hip Complex Dysfunction (LPHCD),</a> Sacroiliac Joint Dysfunction (SIJD), and <a href="https://brookbushinstitute.com/courses/lower-leg-dysfunction" target="_blank" rel="noopener">Lower Extremity Dysfunction (LED)</a>. The research by Vleeming et al., the common attachments on the sacrotuberous ligament, as well as the common behavior relative to dysfunction contributed to the <a id="hypothesis" data-tip="1446" target="_blank" href="/glossary-term/hypothesis" class="glossary">hypothesis</a> of this myofascial synergy.
The <a href="https://brookbushinstitute.com/courses/gluteus-maximus" target="_blank" rel="noopener">gluteus maximus</a> does not behave like other muscles investing in the sacrotuberous ligament and is excluded from the DLS. While most muscles of the DLS have a propensity toward over-activity, the <a href="https://brookbushinstitute.com/courses/gluteus-maximus" target="_blank" rel="noopener">gluteus maximus</a> has a propensity toward under-activity. Further, the <a href="https://brookbushinstitute.com/courses/gluteus-maximus" target="_blank" rel="noopener">gluteus maximus</a> is a <a id="prime-mover" data-tip="1662" target="_blank" href="/glossary-term/prime-mover" class="glossary">prime mover</a>, whereas most of the muscles of the DLS are <a id="synergists" data-tip="1650" target="_blank" href="/glossary-term/synergists" class="glossary">synergists</a>. The <a href="https://brookbushinstitute.com/courses/gluteus-maximus" target="_blank" rel="noopener">gluteus maximus</a> invests heavily in the superficial laminae of the <a id="posterior" data-tip="1565" target="_blank" href="/glossary-term/posterior" class="glossary">posterior</a> layer of the TLF and plays a larger role in the <a href="https://brookbushinstitute.com/courses/posterior-oblique-subsystem-pos" target="_blank" rel="noopener">POS</a>. The relationship between the <a href="https://brookbushinstitute.com/courses/gluteus-maximus" target="_blank" rel="noopener">gluteus maximus</a> and DLS at the sacrotuberous ligament and SIJ may have important implications related to <a id="integration" data-tip="1473" target="_blank" href="/glossary-term/integration" class="glossary">integrated</a> functions of the DLS and <a href="https://brookbushinstitute.com/courses/posterior-oblique-subsystem-pos" target="_blank" rel="noopener">Posterior Oblique Subsystem (POS)</a> such as gait, jumping, and lifting.
Muscles investing in the sacrotuberous ligament:
<ul>
 <li>Multifidus</li>
 <li><a href="https://brookbushinstitute.com/courses/gluteus-maximus"> Gluteus maximus (part of the POS).</a></li>
 <li>Piriformis</li>
 <li>Obturator internus (and deep rotators)</li>
 <li><a href="https://brookbushinstitute.com/courses/biceps-femoris"> Biceps femoris </a></li>
 <li>Semitendinosus</li>
 <li>Semimembranosus</li>
 <li><a href="https://brookbushinstitute.com/courses/adductors"> Adductor magnus </a></li>
</ul>
<a href="https://brookbush.s3.us-east-2.amazonaws.com/wordpress/wp-content/uploads/2012/02/Sacrotuberous-ligament-3.png" target="_blank" rel="noopener"><img src="https://www.datocms-assets.com/25800/1650602633-sacrotuberous-ligament.png" title="The location of the sacrotuberous ligament on the pelvis" alt="The sacrotuberious ligament "> </a>
Sacrotuberous Ligament - this image is from the 20th U.S. edition of Gray&apos;s Anatomy of the Human Body, originally published in 1918 and therefore lapsed into the public domain.

The <a href="https://brookbushinstitute.com/courses/erector-spinae" target="_blank" rel="noopener">erector spinae</a> fills the majority of the cross-sectional area of the extensor retinaculum, is invested in the extensor retinaculum and DL from cranium to sacrum, and invests in the common fascial sheath (composite) of the sacrum running continuous with the sacrotuberous ligament. Although more research is needed investigating the relationship between <a href="https://brookbushinstitute.com/courses/erector-spinae" target="_blank" rel="noopener">erector spinae </a>activity, DL tension/stiffness, and recruitment of the DLS, there is a fair amount of research on <a href="https://brookbushinstitute.com/courses/erector-spinae" target="_blank" rel="noopener">erector spinae</a> function and compensatory behavior.
The <a href="https://brookbushinstitute.com/courses/erector-spinae" target="_blank" rel="noopener">erector spinae</a> is the primary lumbar extensor, especially the iliocostalis thoracis which may produce 70 - 86% of total extensor <a id="torque" data-tip="1294" target="_blank" href="/glossary-term/torque" class="glossary">torque</a> (21, 22). The <a href="https://brookbushinstitute.com/courses/erector-spinae" target="_blank" rel="noopener">erector spinae</a> also contribute to frontal plane stabilization (23), can rotate the spine ipsilaterally (24), contribute to <a id="anterior" data-tip="1566" target="_blank" href="/glossary-term/anterior" class="glossary">anterior</a> <a id="glide" data-tip="1817" target="_blank" href="/glossary-term/glide" class="glossary">shear</a> of the lumbar vertebrae (more with increased lordosis) (22, 25), and may have an effect or be affected by the ribs and costovertebral joints (26). The iliocostalis has a higher <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> spindle density than the multifidus, demonstrating that <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> spindle density increases from the most <a id="medial" data-tip="1568" target="_blank" href="/glossary-term/medial" class="glossary">medial</a> fibers to the most <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> fibers of the lumbar extensors (26, 27). Unlike the multifidus, asymmetrical activity of the iliocostalis is common when challenged by asymmetric loads (128, 129). For example, holding weight in the right-hand increases left iliocostalis activity, but <a id="bilateral" data-tip="1552" target="_blank" href="/glossary-term/bilateral" class="glossary">bilateral</a> multifidus activity. This behavior implies that the erector spinae behaves more like a <a id="prime-mover" data-tip="1662" target="_blank" href="/glossary-term/prime-mover" class="glossary">prime mover</a> or large force generator, and the multifidus more like a segmental <a id="stabilizers" data-tip="1653" target="_blank" href="/glossary-term/stabilizers" class="glossary">stabilizer</a>.
The behavior of the <a href="https://brookbushinstitute.com/courses/erector-spinae" target="_blank" rel="noopener">erector spinae</a> relative to dysfunction is complex, but is similar to other muscles categorized as &quot;short/over-active&quot;. In those exhibiting signs of chronic low back pain the <a href="https://brookbushinstitute.com/courses/erector-spinae" target="_blank" rel="noopener">erector spinae</a> exhibit less activity in lumbar extended positions (30), produce less <a id="torque" data-tip="1294" target="_blank" href="/glossary-term/torque" class="glossary">torque</a> and fatigue faster during isometric extension (31-33), are more active during static standing (34 - 36), peak higher during flexion, spontaneously discharge around <a id="hypermobility" data-tip="1679" target="_blank" href="/glossary-term/hypermobility" class="glossary">hypermobile</a> segments (34, 36), and remain active for longer after a lift (37). Further, changes in motor behavior include delayed activity during lifting tasks (28, 38) and <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger point</a> development (39, 40). Additional findings that may have implications for practice include a study by Renkawitz et al. that showed an imbalance in EMG activity between right and left sides in those exhibiting low back pain (41), Nourbkhsh et al. found that extensor endurance had the highest correlation with low back pain when compared to 16 additional mechanical factors (other variables were also strongly correlated) (42), and Cooper et al. found <a href="https://brookbushinstitute.com/courses/erector-spinae" target="_blank" rel="noopener">erector spinae</a> atrophy in those with chronic low back pain (43). Based on these findings the BI recommends treating the <a href="https://brookbushinstitute.com/courses/erector-spinae" target="_blank" rel="noopener">erector spinae</a> similar to other muscles of the DLS, using <a id="release" data-tip="1249" target="_blank" href="/glossary-term/release" class="glossary">release</a>, mobilization, and lengthening techniques to address increased activity and reductions in <a id="mobility" data-tip="1455" target="_blank" href="/glossary-term/mobility" class="glossary">mobility</a>. Core <a id="integration" data-tip="1472" target="_blank" href="/glossary-term/integration" class="glossary">integration</a> and subsystem <a id="integration" data-tip="1472" target="_blank" href="/glossary-term/integration" class="glossary">integration</a> techniques should be relied upon to address atrophy and core <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> endurance. It may also be prudent to <a id="assessment" data-tip="1486" target="_blank" href="/glossary-term/assessment" class="glossary">assess</a> prior to any sign of injury (prehab), as a study by Lee et al (1999) demonstrated that imbalance between spine flexors and extensors was a risk factor for low back injury in a 5-year <a id="prospective-study" data-tip="1414" target="_blank" href="/glossary-term/prospective-study" class="glossary">prospective study</a> (44).
Due to the size and attachments of the <a href="https://brookbushinstitute.com/courses/erector-spinae" target="_blank" rel="noopener">erector spinae</a> from cranium to sacrotuberous ligament, its function as the <a id="prime-mover" data-tip="1662" target="_blank" href="/glossary-term/prime-mover" class="glossary">prime mover</a> in lumbar extension, and the significant research detailing the attributes of its compensatory over-active behavior, the <a href="https://brookbushinstitute.com/courses/erector-spinae" target="_blank" rel="noopener">erector spinae</a> is thought of as a keystone structure in the DLS. Assessed alterations in activity in length of the <a href="https://brookbushinstitute.com/courses/erector-spinae" target="_blank" rel="noopener">erector spinae</a> should be attributed to all muscles investing in the DL and treated accordingly.

The <a href="https://brookbushinstitute.com/courses/biceps-femoris" target="_blank" rel="noopener">biceps femoris</a>, <a href="https://brookbushinstitute.com/courses/adductors" target="_blank" rel="noopener">adductor magnus</a>, and piriformis all have attachments to the sacrotuberous ligament. There is a significant amount of research on the <a href="https://brookbushinstitute.com/courses/biceps-femoris" target="_blank" rel="noopener">biceps femoris</a>; however, research on the piriformis, and <a href="https://brookbushinstitute.com/courses/adductors" target="_blank" rel="noopener">adductor magnus</a> is lacking. Further, there is no research on the activity of the deep rotators which are presumed to behave similarly to the piriformis. Clinically, it has been observed that these muscles behave similar to one another, in a manner congruent with the behavior of the DLS, and addressing all of these muscles together seems to improve outcomes related to DLS and sacroiliac joint (SIJ) dysfunction.
<img title="Image of the piriformis muscle (but also note the bicep femoris and posterior fibers of adductor magnus)" src="https://www.datocms-assets.com/25800/1642102018-piriformis.png" width="251" height="682" alt="The piriformis muscle on the sacrum and femur">
Several studies have demonstrated increased <a href="https://brookbushinstitute.com/courses/biceps-femoris" target="_blank" rel="noopener">biceps femoris</a> activity relative to decreased <a href="https://brookbushinstitute.com/courses/gluteus-maximus" target="_blank" rel="noopener">gluteus maximus</a> activity in those exhibiting <a href="https://brookbushinstitute.com/video/knees-bow-in-breakdown" target="_blank" rel="noopener">knees bow in </a>(functional valgus), an <a href="https://brookbushinstitute.com/video/overhead-squat-assessment-9-anterior-pelvic-tilt-excessive-lordosis" target="_blank" rel="noopener">anterior pelvic tilt</a>, lumbar spine <a id="stability" data-tip="1193" target="_blank" href="/glossary-term/stability" class="glossary">instability</a>, sacroiliac joint dysfunction, and/or low back pain (42, 45 - 49). These studies may be evidence of a relationship between the DLS and <a href="https://brookbushinstitute.com/courses/posterior-oblique-subsystem-pos" target="_blank" rel="noopener">POS</a> that results in <a href="https://brookbushinstitute.com/courses/posterior-oblique-subsystem-pos" target="_blank" rel="noopener">POS </a> inhibition and <a id="synergistic-dominance" data-tip="1643" target="_blank" href="/glossary-term/synergistic-dominance" class="glossary">synergistic dominance</a> of the DLS. <a id="release" data-tip="1249" target="_blank" href="/glossary-term/release" class="glossary">Release</a> and stretching may be effective ways to treat this change in activity. A study by Hasegawa et al. on the relative activity of <a href="https://brookbushinstitute.com/courses/knee" target="_blank" rel="noopener">knee</a> musculature demonstrated that stretching the <a href="https://brookbushinstitute.com/courses/biceps-femoris" target="_blank" rel="noopener">biceps femoris</a> resulted in a relative increase in vastus medialis obliquus (VMO) activity (49). This begs consideration of whether stretching resolved an over-activity of the <a href="https://brookbushinstitute.com/courses/biceps-femoris" target="_blank" rel="noopener">biceps femoris</a> that was reciprocally inhibiting its functional <a id="antagonists" data-tip="1705" target="_blank" href="/glossary-term/antagonists" class="glossary">antagonist</a> (<a href="https://brookbushinstitute.com/article/quadriceps-vastus-muscles" target="_blank" rel="noopener">VMO</a>), and whether similar changes in activity would be observed at the <a href="https://brookbushinstitute.com/article/hip-joint" target="_blank" rel="noopener">hip</a>. Further, foam rolling the hamstrings has been shown to be an effective strategy for increasing <a id="extensibility-2" data-tip="1308" target="_blank" href="/glossary-term/extensibility-2" class="glossary">extensibility</a> (50). Note, based on the relative increase in length in static <a id="posture" data-tip="1658" target="_blank" href="/glossary-term/posture" class="glossary">posture</a> in those exhibiting an <a href="https://brookbushinstitute.com/video/overhead-squat-assessment-9-anterior-pelvic-tilt-excessive-lordosis" target="_blank" rel="noopener">anterior pelvic tilt</a>, the Brookbush Institute (BI) suggests that better long-term results may be noted with <a id="release" data-tip="1249" target="_blank" href="/glossary-term/release" class="glossary">Release</a> techniques alone, despite stretching providing some short-term benefits.
Very few studies have investigated the activity of the piriformis, and no studies exist investigating the deep rotators to our knowledge. This is likely due to their location deep to the thick <a href="https://brookbushinstitute.com/courses/gluteus-maximus" target="_blank" rel="noopener">gluteus maximus</a>. It is hypothesized that the deep rotators and piriformis behave similarly. The piriformis has been shown to be more active during external rotation, abduction, and extension of the femur, and increased <a id="tension" data-tip="1229" target="_blank" href="/glossary-term/tension" class="glossary">tension</a> will contribute to stabilization (<a id="compression" data-tip="1595" target="_blank" href="/glossary-term/compression" class="glossary">compression</a>) of the sacroiliac joint (SIJ) (51-54). Note, the piriformis is unique among DLS muscles due to its ability to <a id="compression" data-tip="1597" target="_blank" href="/glossary-term/compression" class="glossary">compress</a> the SIJ via muscular action, as well as increase <a id="tension" data-tip="1229" target="_blank" href="/glossary-term/tension" class="glossary">tension</a> in the sacrotuberous ligament. Based on function, over-activity and adaptive shortening of these muscles would contribute to the compensation patterns <a href="https://brookbushinstitute.com/video/overhead-squat-assessment-7-knees-bow-out" target="_blank" rel="noopener"> Knees Bow Out </a> (Functional Varus), <a href="https://brookbushinstitute.com/video/overhead-squat-assessment-15-sign-clusters-asymmetrical-weight-shift" target="_blank" rel="noopener">Asymmetrical Weight Shift</a> to the opposite side, and SIJ stiffness. Clinically, palpation of the piriformis would imply this <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> is commonly over-active, even in cases of, <a href="https://brookbushinstitute.com/courses/lower-leg-dysfunction" target="_blank" rel="noopener"> LED</a> and <a href="https://brookbushinstitute.com/courses/lumbo-pelvic-hip-complex-dysfunction-lphcd" target="_blank" rel="noopener">LPHCD</a> resulting in <a href="https://brookbushinstitute.com/video/knees-bow-in-breakdown" target="_blank" rel="noopener">Knees Bow In </a>and a presumed increase in length. There is some research to <a id="base-of-support" data-tip="1197" target="_blank" href="/glossary-term/base-of-support" class="glossary">support</a> that piriformis (and perhaps <a href="=" target="_blank" rel="noopener">deep rotator</a>) <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> are common, occurring in 25 - 50% of the population (49, 55). <a id="release" data-tip="1249" target="_blank" href="/glossary-term/release" class="glossary">Release</a> has proven clinically effective; however, due to a presumed increase in length in those exhibiting dysfunction, stretching is only recommended if <a id="release" data-tip="1249" target="_blank" href="/glossary-term/release" class="glossary">Release</a> techniques do not return normal <a id="extensibility-2" data-tip="1308" target="_blank" href="/glossary-term/extensibility-2" class="glossary">extensibility</a>.
There is a void in the body of research regarding the activity of the <a href="https://brookbushinstitute.com/courses/adductors" target="_blank" rel="noopener">adductor magnus.</a> Three older publications suggest that despite the <a href="https://brookbushinstitute.com/courses/adductors" target="_blank" rel="noopener">adductor group</a> being active during the entirety of the gait cycle, the <a id="posterior" data-tip="1565" target="_blank" href="/glossary-term/posterior" class="glossary">posterior</a> or &quot;ischiocondylar&quot; head of the <a href="https://brookbushinstitute.com/courses/adductors" target="_blank" rel="noopener">adductor magnus</a> has spikes and troughs in activity similar to the <a href="https://brookbushinstitute.com/courses/biceps-femoris" target="_blank" rel="noopener">hamstrings </a> (49, 56, 57). That is, the <a id="posterior" data-tip="1565" target="_blank" href="/glossary-term/posterior" class="glossary">posterior</a> head of the <a href="https://brookbushinstitute.com/courses/adductors" target="_blank" rel="noopener">adductor magnus</a> is an extensor, an external rotator, and is active during mid stance, push-off, and the late swing phase of gait. Anatomically, this <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> does share an origin with the <a href="https://brookbushinstitute.com/courses/biceps-femoris" target="_blank" rel="noopener">biceps femoris</a> on the sacrotuberous ligament and has neural innervation from the sciatic <a id="nerve-cell" data-tip="1361" target="_blank" href="/glossary-term/nerve-cell" class="glossary">nerve</a> via the tibial <a id="nerve-cell" data-tip="1361" target="_blank" href="/glossary-term/nerve-cell" class="glossary">nerve</a> (much like the hamstrings). Throughout the Brookbush Institute content, the term &quot;<a href="https://brookbushinstitute.com/courses/adductors" target="_blank" rel="noopener">adductor magnus</a> &quot; is used to reference the <a id="posterior" data-tip="1565" target="_blank" href="/glossary-term/posterior" class="glossary">posterior</a> head of the <a href="https://brookbushinstitute.com/courses/adductors" target="_blank" rel="noopener">adductor magnus</a>, and this <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> is addressed in the same manner as the <a href="https://brookbushinstitute.com/courses/biceps-femoris" target="_blank" rel="noopener">biceps femoris</a>, as well as the piriformis and deep rotators ). The BI most often recommends <a id="release" data-tip="1249" target="_blank" href="/glossary-term/release" class="glossary">release</a> techniques for these muscles.
Note: similar to labeling the <a href="https://brookbushinstitute.com/courses/erector-spinae" target="_blank" rel="noopener">erector spinae</a> as the keystone structure relative to the DL, the <a href="https://brookbushinstitute.com/courses/biceps-femoris" target="_blank" rel="noopener">biceps femoris</a> is the keystone structure of the muscles investing in the sacrotuberous ligament. This is due to the muscle&apos;s relative size, the attachments from sacrotuberous ligament to fibular head, the significant amount of research detailing the muscle&apos;s activity relative to the <a href="https://brookbushinstitute.com/courses/gluteus-maximus" target="_blank" rel="noopener">gluteus maximus</a>, and the relative ease of assessing this <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> compared to other muscles investing in the sacrotuberous ligament. Assessed alterations in activity and length of the <a href="https://brookbushinstitute.com/courses/biceps-femoris" target="_blank" rel="noopener">biceps femoris </a>should be attributed to all muscles investing in the sacrotuberous ligament and treated accordingly.

The fibularis muscles extend the DLS from <a href="https://brookbushinstitute.com/courses/knee" target="_blank" rel="noopener">knee</a> to <a href="https://brookbushinstitute.com/courses/ankle-joint-talocrural-subtalor-tibiofibular-joints" target="_blank" rel="noopener">ankle</a> via fascial continuity with the <a href="https://brookbushinstitute.com/courses/biceps-femoris" target="_blank" rel="noopener">biceps femoris</a> at the fibular head. This may imply the DLS has an important role in core function, as well as knee, <a id="proximal" data-tip="1564" target="_blank" href="/glossary-term/proximal" class="glossary">proximal</a> and <a id="distal" data-tip="1563" target="_blank" href="/glossary-term/distal" class="glossary">distal</a> tibiofibular joint, and ankle function.
Unfortunately, the activity and behavior of the fibularis muscles has not been well researched. Based on their moment arm and size, these muscles are the strongest evertors (pronators) of the ankle/foot but are relatively weak plantar flexors (58, 59). This may imply that these muscles contribute more to adjusting the foot to accommodate uneven terrain and less to propulsion, and further, over-activity of the fibularis muscles may contribute more to <a href="https://brookbushinstitute.com/video/overhead-squat-assessment-4-feet-flat-breakdown" target="_blank" rel="noopener">feet flatten </a> (functional pes planus) than to a <a href="https://brookbushinstitute.com/video/dorsiflexion-goniometry" target="_blank" rel="noopener"> loss of dorsiflexion</a>.
The <a href="https://brookbushinstitute.com/courses/fibularis-muscles" target="_blank" rel="noopener">fibularis muscles</a> are categorized as over-active based on the prevalence of <a href="https://brookbushinstitute.com/video/overhead-squat-assessment-4-feet-flat-breakdown" target="_blank" rel="noopener">feet flatten </a> (functional pes planus) in those exhibiting <a href="https://brookbushinstitute.com/courses/lower-leg-dysfunction" target="_blank" rel="noopener"> Lower Extremity Dysfunction (LED)</a>. Studies have noted that the <a href="https://brookbushinstitute.com/glossary/excitation-threshold/" target="_blank" rel="noopener">excitation threshold</a> of the fibularis muscles increases (making it harder to activate) and that reflex contraction in response to <a href="https://brookbushinstitute.com/glossary/posture/" target="_blank" rel="noopener">postural</a> challenges is delayed in those exhibiting dysfunction (chronic ankle sprains) (60 - 64). Although these traits would seem to indicate &quot;under-activity&quot; more research is needed to investigate activity relative to other musculature of the lower extremity during various functional tasks. Labeling and categorization is complex, and although labeling the fibularis muscles as under-active may seem easiest given the above research, these initial studies have similarities to the attributes exhibited by the more thoroughly studied (and over-active) <a href="https://brookbushinstitute.com/courses/erector-spinae" target="_blank" rel="noopener">erector spinae</a> muscles. Until further research can address these gaps and compare interventions intended to address fibularis <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> dysfunction, the BI recommends addressing these muscles as short/over-active with special consideration given to &quot;reactive activation&quot; exercises (for the <a href="https://brookbushinstitute.com/courses/tibialis-posterior-activation" target="_blank" rel="noopener">invertors</a> and <a href="https://brookbushinstitute.com/courses/gluteus-medius-activation-progression" target="_blank" rel="noopener">glute complex).</a><a href="https://brookbush.s3.us-east-2.amazonaws.com/wordpress/wp-content/uploads/2012/02/Thoracolumbar-Fascia-Gray.png" target="_blank" rel="noopener"></a>

There is some disagreement regarding whether the <a href="https://brookbushinstitute.com/courses/rhomboids" target="_blank" rel="noopener">rhomboid</a> fascia is a separate epimysial fascial sheath, the <a id="posterior" data-tip="1565" target="_blank" href="/glossary-term/posterior" class="glossary">posterior</a> layer of the TLF runs underneath the rhomboids, or whether the DL and the superficial layer of the TLF envelop and are continuous with the <a href="https://brookbushinstitute.com/courses/rhomboids" target="_blank" rel="noopener">rhomboid</a> fascia as described by Barker et al. and Vleeming et al. (2, 65 - 68). In this article, the <a href="https://brookbushinstitute.com/courses/rhomboids" target="_blank" rel="noopener">rhomboids</a> are treated as if the <a href="https://brookbushinstitute.com/courses/rhomboids" target="_blank" rel="noopener">rhomboid</a> fascia runs continuous with the DL. The behavior of the <a href="https://brookbushinstitute.com/courses/rhomboids" target="_blank" rel="noopener">rhomboids</a>&#xA0;matches the activity of the other muscles of the DLS, and the inclusion of this <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> inspires consideration of how subsystems may affect scapular motion.
The <a href="https://brookbushinstitute.com/courses/rhomboids" target="_blank" rel="noopener">rhomboid</a>s&#xA0;behave as might be expected from a <a id="synergists" data-tip="1854" target="_blank" href="/glossary-term/synergists" class="glossary">synergist</a> for retraction, elevation, and downward rotation. Their activation cannot be separated from other scapular movers, and their activity increases with less <a href="https://brookbushinstitute.com/courses/trapezius-muscle" target="_blank" rel="noopener">trapezius</a> activity during arm elevation (70, 71). They play a role in positioning the scapula for <a id="optimal" data-tip="1571" target="_blank" href="/glossary-term/optimal" class="glossary">optimal</a> glenohumeral mechanics during arm motion, are more active during &quot;<a href="https://brookbushinstitute.com/article/back-pulling-movement-patterns" target="_blank" rel="noopener">rows/pulling</a>&quot; (retraction), and less active during <a href="https://brookbushinstitute.com/article/shoulderoverhead-pressing-patterns" target="_blank" rel="noopener">arm elevation/overhead pressing </a>or <a href="https://brookbushinstitute.com/article/chestpushing-movements" target="_blank" rel="noopener">pushing </a>(72 - 75). <a href="https://brookbushinstitute.com/courses/rhomboids" target="_blank" rel="noopener">Rhomboid</a>&#xA0;activity is likely important for stabilization as it was noted that activity increases with gripping (finger flexor activation), and increased re-activity (decreased latency) was noted in the trained arm of pitchers and the dominant arm of untrained individuals (76, 77).
There are very few studies related to the <a href="https://brookbushinstitute.com/courses/rhomboids" target="_blank" rel="noopener">rhomboid</a>s&#xA0;compensatory behavior in those exhibiting signs of dysfunction. This is likely due to their position deep to the <a href="https://brookbushinstitute.com/courses/trapezius-muscle" target="_blank" rel="noopener">trapezius</a>&#xA0;muscles. Research does suggest that their behavior does not change in those exhibiting <a id="anterior" data-tip="1566" target="_blank" href="/glossary-term/anterior" class="glossary">anterior</a> shoulder instability; however, in a study by Yoo et al., pain pressure threshold decreased in those working at a computer for just 15 minutes and continued to increase for the 60-minute duration of the study (78, 79). This may imply that compensatory changes in activity and length of the <a href="https://brookbushinstitute.com/courses/rhomboids" target="_blank" rel="noopener">rhomboids</a>&#xA0;are more heavily influenced by changes in <a href="https://brookbushinstitute.com/courses/sternoclavicular-acromioclavicular-scapulothoracic-joints" target="_blank" rel="noopener">scapula</a> and thoracic spine position (slouched <a id="posture" data-tip="1658" target="_blank" href="/glossary-term/posture" class="glossary">posture</a>), and less influenced by <a href="https://brookbushinstitute.com/courses/shoulder-glenohumeral-joint" target="_blank" rel="noopener">shoulder</a> dysfunction. Further, studies have demonstrated that the <a href="https://brookbushinstitute.com/courses/rhomboids" target="_blank" rel="noopener">rhomboid&apos;s</a> activity increases with inhibition of the <a href="https://brookbushinstitute.com/courses/trapezius-muscle" target="_blank" rel="noopener">trapezius</a> muscles, and research has demonstrated a higher rate of perceived exertion when the <a href="https://brookbushinstitute.com/courses/rhomboids" target="_blank" rel="noopener">rhomboids</a> and other synergistic muscles were relied upon for movement (71, 80). The function and evidence of altered behavior suggest this <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> is likely over-active in those exhibiting dysfunction, acting as an <a id="synergistic-dominance" data-tip="1645" target="_blank" href="/glossary-term/synergistic-dominance" class="glossary">over-active synergist</a> for inhibition of the <a href="https://brookbushinstitute.com/courses/trapezius-muscle" target="_blank" rel="noopener">trapezius</a> <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a>.
<img src="https://www.datocms-assets.com/25800/1647365185-1642024592-rhomboids.png" title="The location and attachment of the rhomboid muscles on the scapula and thoracic spine" alt="The rhomboid muscles sitting on the scapula and thoracic spine">

The deep lamina of the <a id="posterior" data-tip="1565" target="_blank" href="/glossary-term/posterior" class="glossary">posterior</a> layer continues to become the investing layer of the cervical fascia, covering the paraspinal muscles including the splenius cervicis and capitis as it blends with surrounding cervical fascias; eventually fusing with the <a id="cephalad" data-tip="1559" target="_blank" href="/glossary-term/cephalad" class="glossary">cranial</a> <a id="base-of-support" data-tip="1196" target="_blank" href="/glossary-term/base-of-support" class="glossary">base</a> (70, 81). Some evidence exists that the DL is not well developed above the border of the serratus <a id="posterior" data-tip="1565" target="_blank" href="/glossary-term/posterior" class="glossary">posterior</a> <a id="superior" data-tip="1570" target="_blank" href="/glossary-term/superior" class="glossary">superior</a>, which would exclude the cervical musculature from the DLS (67). We have chosen to treat the splenius cervicis and capitis as members of the DLS due to the potential for fascial continuity and the propensity of these muscles to behave similar to and in conjunction with the <a href="https://brookbushinstitute.com/courses/erector-spinae" target="_blank" rel="noopener">erector spinae</a>.
The spleneii contribute to extension and <a id="ipsilateral" data-tip="1550" target="_blank" href="/glossary-term/ipsilateral" class="glossary">ipsilateral</a> rotation of the cervical spine and head (82 - 85). A study by Vasavada et al. reported the splenii among the cervical muscles with the largest extension moment arms (85). Unlike the larger <a href="https://brookbushinstitute.com/courses/trapezius-muscle" target="_blank" rel="noopener">upper trapezius</a> muscles, the splenii do not appear to be inhibited by <a id="antagonists" data-tip="1705" target="_blank" href="/glossary-term/antagonists" class="glossary">antagonist</a> activity, as two studies demonstrate that resisted flexion (and diagonal flexion) resulted in maintenance of low-level activity throughout (86 - 87). These studies imply that the splenii can ipsilaterally rotate the cervical spine, but are likely more important as extensors and may play a role in stabilization of the spine during flexion.
Those with cervical dysfunction exhibit altered splenii activity. Two studies report a decrease in activity and force when pain is experimentally induced via injection (88-89). Although these studies may aid in our understanding of compensatory behavior relative to acute injury; this decrease in activity following injection is noted in similar studies on other muscles. This may imply that injection alone results in a decrease in activity. The behavior of the splenii relative to cervical dysfunction is more nuanced. Although chronic forward head <a id="posture" data-tip="1658" target="_blank" href="/glossary-term/posture" class="glossary">posture</a> results in a decrease in cervical <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> activity and force overall (90), an increase in splenii activity (and <a href="https://brookbushinstitute.com/courses/trapezius-muscle" target="_blank" rel="noopener">upper trapezius)</a> is noted during protraction of the cervical spine, and/or when neutral <a id="posture" data-tip="1658" target="_blank" href="/glossary-term/posture" class="glossary">posture</a> is compared to forward head <a id="posture" data-tip="1658" target="_blank" href="/glossary-term/posture" class="glossary">posture</a> (91). Further, a study by Lindstr&#xF8;m et al., demonstrated a strong correlation between cervical pain and an increase in splenii (and <a href="https://brookbushinstitute.com/courses/trapezius-muscle" target="_blank" rel="noopener">upper trapezius</a>) co-activation during resisted forward flexion (92). Splenii <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> are common, slightly more common in those exhibiting cervical radiculopathy, and may be related specifically to C4/C5 lesions (93, 94).
These traits imply that the splenii are commonly over-active; however, improving lower cervical extension strength is an important component of any program with the intent of reducing forward head <a id="posture" data-tip="1658" target="_blank" href="/glossary-term/posture" class="glossary">posture</a>. A study by Schomacher et al. demonstrated that during cervical extension exercise (<a href="https://brookbushinstitute.com/courses/deep-cervical-flexor-activation" target="_blank" rel="noopener">DCF Activation</a>), extensor activity may be higher at the segment resisted (95). It is recommended that <a id="release" data-tip="1249" target="_blank" href="/glossary-term/release" class="glossary">release</a> techniques are implemented first, to reduce activity and decrease <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger point</a> <a id="sensitivity" data-tip="1226" target="_blank" href="/glossary-term/sensitivity" class="glossary">sensitivity</a>, followed by <a href="https://brookbushinstitute.com/courses/deep-cervical-flexor-activation" target="_blank" rel="noopener">resisted cervical retraction</a> with <a id="a-band" data-tip="1347" target="_blank" href="/glossary-term/a-band" class="glossary">a band</a> placed low on the neck. Note, studies have demonstrated that more reps at lower loads to fatigue increases activity more than higher loads with low rep ranges (96).
<a href="https://brookbush.s3.us-east-2.amazonaws.com/wordpress/wp-content/uploads/2014/12/Cervical-Fascia.png" target="_blank" rel="noopener"> <img src="https://brookbush.s3.us-east-2.amazonaws.com/wordpress/wp-content/uploads/2014/12/Cervical-Fascia.png" alt="A cross sectional image of the cervcial muscles" title="The cervical muscles including the splenius, trapezius, and levator scapulae"> </a> By Henry Vandyke Carter - Henry Gray (1918) Anatomy of the Human Body (See &quot;Book&quot; section below) Bartleby.com: Gray&apos;s Anatomy, Plate 384, Public Domain, https://commons.wikimedia.org/w/index.php?curid=561537

<ul>
 <li>Muscles investing in the deep laminae (DL) of the <a id="posterior" data-tip="1565" target="_blank" href="/glossary-term/posterior" class="glossary">posterior</a> layer of the thoracolumbar fascia (TLF) include the splenius capitis and splenius cervicis, superficial fascia of the rhomboids, and erector spinae.</li>
 <li>The DL may serve to reinforce the extensor retinaculum as it inflates to optimize fiber direction and moment arms, restricts radial expansion of the erector spinae, and aids in eccentric deceleration of flexion.</li>
 <li>Muscles investing in the sacrotuberous ligament include the piriformis obturator internus (and deep rotators), biceps femoris, and adductor magnus.</li>
 <li>The various subsystems may interact via fusions between the layers of the TLF at junctions like the <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> raphe, sacral composite, and sacrotuberous ligament.</li>
 <li>Research has demonstrated that <a id="glide" data-tip="1817" target="_blank" href="/glossary-term/glide" class="glossary">shear</a> strain (<a id="gliding-joint" data-tip="1835" target="_blank" href="/glossary-term/gliding-joint" class="glossary">gliding</a>) between <a id="posterior" data-tip="1565" target="_blank" href="/glossary-term/posterior" class="glossary">posterior</a> layers of the TLF may be reduced in those exhibiting dysfunction (11, 12). Direct pressure via a foam <a id="roll" data-tip="1602" target="_blank" href="/glossary-term/roll" class="glossary">roll</a> or manual techniques may increase extensibility; however, stretching may not (13 - 15).</li>
 <li>The erector spinae is thought of as a keystone structure of the muscles investing in the DL due to its size and attachments from cranium to sacrotuberous ligament, its function as a <a id="prime-mover" data-tip="1662" target="_blank" href="/glossary-term/prime-mover" class="glossary">prime mover</a> in lumbar extension, and the significant research detailing the attributes exhibited when dysfunction results in over-activity. Assessed alterations in activity in length of the erector spinae should be attributed to all muscles investing in the DL and treated accordingly.</li>
 <li>The biceps femoris is considered a keystone structure of the muscles investing in the sacrotuberous ligament due to the muscles relative size, the attachments from sacrotuberous ligament to fibular head, the significant amount of research detailing the muscle&apos;s activity relative to the gluteus maximus, and the relative ease of assessing this <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> compared to other muscles investing in the sacrotuberous ligament. Assessed alterations in activity in length of the biceps femoris should be attributed to all muscles investing in the sacrotuberous ligament and treated accordingly.</li>
 <li>The fibularis muscles extend the DLS from knee to ankle via fascial continuity with the biceps femoris at the fibular head.</li>
 <li>The rhomboids extend the DLS from the thoracic spine to scapula, inspiring consideration of core subsystem involvement in scapular motion.</li>
 <li>The splenius capitis and splenius cervicis reinforce the notion that the DLS extends up to the cranium, inspiring the consideration of a foot-to-head subsystem.</li>
 <li>All muscles of the DLS have a propensity toward over-activity:
 <ul>
 <li>The upper body muscles of the DLS (those investing in the DL) have a propensity to be &quot;short&quot; in <a id="posture" data-tip="1659" target="_blank" href="/glossary-term/posture" class="glossary">postural</a> dysfunction - splenius capitis and splenius cervicis, rhomboids, and erector spinae</li>
 <li>The lower body <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> (those investing in the sacrotuberous ligament have a propensity to be long) - piriformis, obturator internus (and deep rotators), biceps femoris, and adductor magnus</li>
 <li>Except for the fibularis muscles</li>
 </ul>
 </li>
</ul>
<img title="A runner with a potential of having an overactive deep longitudinal subsystem" src="https://www.datocms-assets.com/25800/1649652884-running.jpg" alt="Image of a runner with potential deep longitudinal subsystem dominance"> Note the female runner and potential DLS dominance (knee valgus and tibial external rotation in swing phase).

<h3> Proprioception and Gait </h3>
The Deep Longitudinal Subsystem (DLS) eccentrically decelerates leg swing during gait, and may act as a proprioceptive mechanism to rate heel strike force, and reflexively aid in the recruitment of propulsion muscles. During the swing phase of gait (hip flexion/knee extension), <a id="tension" data-tip="1229" target="_blank" href="/glossary-term/tension" class="glossary">tension</a> and activity increase in the lower extremity muscles of the DLS, peaking during heel strike and the initiation of propulsion (97 - 101). Research has also demonstrated that the stretch-shortening cycle (<a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> spindle excitation) and afferentation (sural <a id="nerve-cell" data-tip="1361" target="_blank" href="/glossary-term/nerve-cell" class="glossary">nerve</a>, bottom of foot) at the end of the swing phase alters recruitment of the <a href="https://brookbushinstitute.com/courses/biceps-femoris" target="_blank" rel="noopener">biceps femoris </a> (102-103). Due to a &quot;law of parsimony&quot; hierarchy in the body, lower-level activities often rely on smaller <a id="synergists" data-tip="1650" target="_blank" href="/glossary-term/synergists" class="glossary">synergists</a> for motion, and larger <a id="prime-mover" data-tip="1663" target="_blank" href="/glossary-term/prime-mover" class="glossary">prime movers</a> are not recruited unless motion is resisted by an external force. In this way, the <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> spindle excitation and additional afferentation from structures of the DLS during heel strike may be the difference between relying only on the DLS, or additionally recruiting larger muscles from the <a href="https://brookbushinstitute.com/courses/posterior-oblique-subsystem-pos" target="_blank" rel="noopener"> </a><a id="posterior" data-tip="1565" target="_blank" href="/glossary-term/posterior" class="glossary">Posterior</a> Oblique Subsystem (POS) during tasks like walking uphill or stair-climbing (101 - 104).
<h3> Sacroiliac Joint (SIJ) Stability during Functional Tasks </h3>
As mentioned above, increased activity of the DLS muscles increases <a id="tension" data-tip="1229" target="_blank" href="/glossary-term/tension" class="glossary">tension</a> in the sacrotuberous ligament, which may resist <a id="nutation" data-tip="1213" target="_blank" href="/glossary-term/nutation" class="glossary">nutation</a>, contribute to <a href="https://brookbushinstitute.com/glossary/force-closure/" target="_blank" rel="noopener">force closure</a>, and increase stiffness of the sacroiliac joint (SIJ) (16, 17, 19, 20, 105). This may have important implications relative to SIJ stabilization for gait and other high-intensity activities. For example, as the innominate posteriorly rotates on the sacrum (<a id="nutation" data-tip="1213" target="_blank" href="/glossary-term/nutation" class="glossary">nutation</a>) during the swing phase of gate, <a id="tension" data-tip="1229" target="_blank" href="/glossary-term/tension" class="glossary">tension</a> develops in the lower extremity DLS muscles increasing <a id="tension" data-tip="1229" target="_blank" href="/glossary-term/tension" class="glossary">tension</a> in the sacrotuberous ligament. The <a id="tension" data-tip="1229" target="_blank" href="/glossary-term/tension" class="glossary">tension</a> may aid in eccentrically decelerating <a id="nutation" data-tip="1213" target="_blank" href="/glossary-term/nutation" class="glossary">nutation</a> and is highest around heel strike (97 - 101) when increased rigidity of the SIJ and pelvis would be most beneficial for transferring force from hip muscles to the lower extremity for the initiation of propulsion. This same mechanism would be beneficial for higher intensity tasks such as stair-climbing, sprinting, <a href="https://brookbushinstitute.com/video/box-jump" target="_blank" rel="noopener"> jumping</a>, <a href="https://brookbushinstitute.com/video/back-squat" target="_blank" rel="noopener"> squatting</a>, or <a href="https://brookbushinstitute.com/video/deadlift-progressions-cueing-and-questionable-variations" target="_blank" rel="noopener">deadlifting</a> when <a id="stability" data-tip="1191" target="_blank" href="/glossary-term/stability" class="glossary">stability</a> of the pelvis and SIJ may be essential for <a id="optimal" data-tip="1571" target="_blank" href="/glossary-term/optimal" class="glossary">optimal</a> performance and reducing the risk of <a href="https://brookbushinstitute.com/courses/lumbo-pelvic-hip-complex-dysfunction-lphcd" target="_blank" rel="noopener"> Lumbo Pelvic Hip Complex Dysfunction (LPHCD)</a>.
<h3>Secondary system:</h3>
As mentioned above, many of the muscles of the DLS are <a id="synergists" data-tip="1650" target="_blank" href="/glossary-term/synergists" class="glossary">synergists</a>, acting to assist larger prime-movers. This is especially true of the extension mechanism that is essential for gait and lifting. Several studies have demonstrated a correlation between dysfunction, a reduction in relative <a href="https://brookbushinstitute.com/courses/gluteus-maximus" target="_blank" rel="noopener">gluteus maximus</a> activity, and an increase in <a href="https://brookbushinstitute.com/courses/erector-spinae" target="_blank" rel="noopener">lumbar erector</a> and <a href="https://brookbushinstitute.com/courses/biceps-femoris" target="_blank" rel="noopener">biceps femoris</a> activity (106 - 112). Visually, this may present as an increase in the lumbar lordosis during gait, and/or a reliance on lumbar flexion and extension (as opposed to <a href="https://brookbushinstitute.com/courses/hip-joint" target="_blank" rel="noopener">hip</a> flexion and extension) during bent-over lifting. Although it may be important to have an alternative movement pattern or set of motor units to maintain function during fatigued or dysfunctional states, research and practice imply that that dominance of one system results in a decrease in the activity of the other. That is, targeting the muscles of the DLS with strengthening techniques is likely to increase reliance on the DLS, and reduce reliance on the larger more powerful muscles of the <a href="https://brookbushinstitute.com/courses/posterior-oblique-subsystem-pos" target="_blank" rel="noopener"> POS</a>.
Clinically it has been noted that lifting nearer to full <a href="https://brookbushinstitute.com/courses/knee" target="_blank" rel="noopener">knee</a> extension increases reliance on the <a href="https://brookbushinstitute.com/courses/biceps-femoris" target="_blank" rel="noopener">biceps femoris</a>, resisted adduction during squatting, stepping, and gait increases reliance on <a href="https://brookbushinstitute.com/courses/adductors" target="_blank" rel="noopener">adductor magnus</a>, and targeted interventions for any <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> of the DLS prior to functional tasks will increase the targeted muscles activity. To increase reliance on the <a href="https://brookbushinstitute.com/courses/gluteus-maximus" target="_blank" rel="noopener"> gluteus maximus </a> and <a href="https://brookbushinstitute.com/courses/posterior-oblique-subsystem-pos" target="_blank" rel="noopener"> POS</a>, and decrease the activity of the <a href="https://brookbushinstitute.com/courses/erector-spinae" target="_blank" rel="noopener"> lumbar erector </a> and <a href="https://brookbushinstitute.com/courses/biceps-femoris" target="_blank" rel="noopener"> biceps femoris</a>, research suggests the following cues may be beneficial (113 - 117):
<ul>
 <li>Cue &quot;squeezing the glutes&quot;</li>
 <li>Cue the abdominal <a id="drawing-in" data-tip="1580" target="_blank" href="/glossary-term/drawing-in" class="glossary">drawing-in</a> maneuver (<a id="drawing-in" data-tip="1588" target="_blank" href="/glossary-term/drawing-in" class="glossary">ADIM</a>)</li>
 <li>Cue <a id="posterior" data-tip="1565" target="_blank" href="/glossary-term/posterior" class="glossary">posterior</a> tilting (to neutral, do not lift with a <a id="posterior" data-tip="1565" target="_blank" href="/glossary-term/posterior" class="glossary">posterior</a> pelvic tilt)</li>
 <li>Band resisted hip abduction during bridging, squatting, deadlifting, etc.</li>
 <li>Forward lean during <a href="https://brookbushinstitute.com/video/side-stepping-progressions-gluteus-medius-reactive-activation" target="_blank" rel="noopener"> resisted side-stepping</a></li>
</ul>

The DLS is <a id="prone" data-tip="1561" target="_blank" href="/glossary-term/prone" class="glossary">prone</a> to over-activity, specifically becoming <a id="synergistic-dominance" data-tip="1649" target="_blank" href="/glossary-term/synergistic-dominance" class="glossary">synergistically dominant</a> for an inhibited <a href="https://brookbushinstitute.com/courses/posterior-oblique-subsystem-pos" target="_blank" rel="noopener"> </a><a id="posterior" data-tip="1565" target="_blank" href="/glossary-term/posterior" class="glossary">Posterior</a> Oblique Subsystem (POS). Perhaps more than any other subsystem, all of the muscles in this subsystem exhibit the same compensatory behavior (over-activity), many of them also exhibiting a relative increase in length during <a id="posture" data-tip="1659" target="_blank" href="/glossary-term/posture" class="glossary">postural</a> <a id="assessment" data-tip="1480" target="_blank" href="/glossary-term/assessment" class="glossary">assessments</a>. In the Brookbush Institute&apos;s predictive <a id="model" data-tip="1471" target="_blank" href="/glossary-term/model" class="glossary">models</a> of <a href="https://brookbushinstitute.com/courses/lumbo-pelvic-hip-complex-dysfunction-lphcd" target="_blank" rel="noopener"> Lumbo Pelvic Hip Complex Dysfunction (LPHCD)</a>, Sacroiliac Joint Dysfunction (SIJD), and <a href="https://brookbushinstitute.com/courses/lower-leg-dysfunction" target="_blank" rel="noopener"> Lower Extremity dysfunction (LED) </a> this sub-system is categorized as long/over-active (playing no significant role in <a href="https://brookbushinstitute.com/courses/upper-body-dysfunction-ubd" target="_blank" rel="noopener"> Upper Body Dysfunction (UBD))</a>. The most common scenario may be described as inhibition of the <a href="https://brookbushinstitute.com/courses/intrinsic-stabilization-subsystem" target="_blank" rel="noopener"> Intrinsic Stabilization Subsystem (ISS) </a> followed by dominance and over-activity of the <a href="https://brookbushinstitute.com/courses/anterior-oblique-subsystem-aos" target="_blank" rel="noopener"> </a><a id="anterior" data-tip="1566" target="_blank" href="/glossary-term/anterior" class="glossary">Anterior</a> Oblique Subsystem (AOS), leading to altered <a id="reciprocal-inhibition" data-tip="1655" target="_blank" href="/glossary-term/reciprocal-inhibition" class="glossary">reciprocal inhibition</a> and under-activity of the <a href="https://brookbushinstitute.com/courses/posterior-oblique-subsystem-pos" target="_blank" rel="noopener"> </a><a id="posterior" data-tip="1565" target="_blank" href="/glossary-term/posterior" class="glossary">Posterior</a> Oblique Subsystem (POS), and compensatory <a id="synergistic-dominance" data-tip="1643" target="_blank" href="/glossary-term/synergistic-dominance" class="glossary">synergistic dominance</a> and over-activity of the DLS. Evidence of DLS dominance during an <a href="https://brookbushinstitute.com/courses/solutions-table-overhead-squat-assessment" target="_blank" rel="noopener"> Overhead Squat Assessment</a>, may result in <a href="https://brookbushinstitute.com/video/overhead-squat-assessment-4-feet-flat-breakdown" target="_blank" rel="noopener">feet flatten</a>, <a href="https://brookbushinstitute.com/video/overhead-squat-assessment-5-feet-turn-out-breakdown" target="_blank" rel="noopener"> feet turn-out</a>, <a href="https://brookbushinstitute.com/video/overhead-squat-assessment-6-knees-bow-in-breakdown" target="_blank" rel="noopener"> knees bow-in</a>, <a href="https://brookbushinstitute.com/video/overhead-squat-assessment-7-knees-bow-out" target="_blank" rel="noopener"> knees bow-out</a>, <a href="https://brookbushinstitute.com/video/overhead-squat-assessment-8-excessive-forward-lean" target="_blank" rel="noopener"> excessive forward lean</a>, <a href="https://brookbushinstitute.com/video/overhead-squat-assessment-9-anterior-pelvic-tilt-excessive-lordosis" target="_blank" rel="noopener"> </a><a id="anterior" data-tip="1566" target="_blank" href="/glossary-term/anterior" class="glossary">Anterior</a> pelvic tilt, and/or an <a href="https://brookbushinstitute.com/video/overhead-squat-assessment-15-sign-clusters-asymmetrical-weight-shift" target="_blank" rel="noopener">asymmetrical weight shift (AWS)</a>. Dominance of the DLS (and under-activity of the <a href="https://brookbushinstitute.com/courses/posterior-oblique-subsystem-pos" target="_blank" rel="noopener"> POS</a>) is generally most dramatic in those individuals exhibiting <a href="https://brookbushinstitute.com/courses/lumbo-pelvic-hip-complex-dysfunction-lphcd" target="_blank" rel="noopener"> LPHCD</a>, SIJD, and <a href="https://brookbushinstitute.com/courses/lower-leg-dysfunction" target="_blank" rel="noopener"> LED</a>.
<a href="https://brookbush.s3.us-east-2.amazonaws.com/wordpress/wp-content/uploads/2016/11/overhead-squat-assessment-17-sig.jpg" target="_blank" rel="noopener"> <img src="https://brookbush.s3.us-east-2.amazonaws.com/wordpress/wp-content/uploads/2016/11/overhead-squat-assessment-17-sig.jpg" alt="Dr. Brent Brookbush teaches the sign &quot;Posterior Pelvic Tilt&quot; during a lecture on the Overhead Squat Assessment" title="Overhead squat assessment with modification"> </a> OHSA with Modification (Heel Rise)

Compensation and Models of Postural Dysfunction:

Based on available research on individual muscles, the Brookbush Institute&#x2019;s (BI&#x2019;s) predictive <a href="https://brookbushinstitute.com/glossary/model/" target="_blank" rel="noopener">models</a> of <a href="https://brookbushinstitute.com/glossary/movement-impairment/" target="_blank" rel="noopener">postural dysfunction</a>, and observations in practice, this subsystem is categorized as &#x201C; long/over-active &#x201C;. As subsystems are synergies, dynamic multi-segmental <a href="https://brookbushinstitute.com/glossary/posture/" target="_blank" rel="noopener">postural</a> <a href="https://brookbushinstitute.com/glossary/assessment/" target="_blank" rel="noopener">assessment</a> is recommended for determining compensatory activity, muscles assessed as over-active are <a id="release" data-tip="1253" target="_blank" href="/glossary-term/release" class="glossary">released</a>, and strengthening/activation of individual muscles within the over-active subsystem is avoided. The BI uses the research and theory of subsystems as a means of refining core and <a href="https://brookbushinstitute.com/glossary/integration/" target="_blank" rel="noopener">integrated</a> exercise selection. Note, the BI&#x2019;s <a href="https://brookbush.s3.us-east-2.amazonaws.com/wordpress/wp-content/uploads/2015/05/Corrective-Exercise-Template.pdf" target="_blank" rel="noopener"> Corrective Template</a> addresses individual structures prior to addressing subsystems to reduce <a href="https://brookbushinstitute.com/glossary/relative-flexibility/" target="_blank" rel="noopener">relative flexibility</a>, <a href="https://brookbushinstitute.com/glossary/synergistic-dominance/" target="_blank" rel="noopener"> synergistic dominance</a>, and compensatory patterns.
<h3> Assessment: </h3>
The Brookbush Institute&apos;s (BI&#x2019;s) preferred dynamic <a id="posture" data-tip="1659" target="_blank" href="/glossary-term/posture" class="glossary">postural</a> <a id="assessment" data-tip="1478" target="_blank" href="/glossary-term/assessment" class="glossary">assessment</a> is the <a href="https://brookbushinstitute.com/courses/solutions-table-overhead-squat-assessment" target="_blank" rel="noopener"> Overhead Squat </a><a id="assessment" data-tip="1478" target="_blank" href="/glossary-term/assessment" class="glossary">assessment</a> (OHSA). The DLS contributes concentrically to <a href="https://brookbushinstitute.com/courses/ankle-joint-talocrural-subtalor-tibiofibular-joints" target="_blank" rel="noopener">ankle</a> eversion, tibial external rotation, femoral external rotation, relative <a id="nutation" data-tip="1213" target="_blank" href="/glossary-term/nutation" class="glossary">nutation</a> of the sacrum, extension of the spine, and downward rotation of the scapula. Eversion and tibial external rotation may contribute to the signs <a href="https://brookbushinstitute.com/video/overhead-squat-assessment-4-feet-flat-breakdown" target="_blank" rel="noopener">feet flatten</a>, <a href="https://brookbushinstitute.com/video/overhead-squat-assessment-5-feet-turn-out-breakdown" target="_blank" rel="noopener"> feet turn-out</a>&#xA0;and <a href="https://brookbushinstitute.com/video/overhead-squat-assessment-6-knees-bow-in-breakdown" target="_blank" rel="noopener">knees bow in (functional valgus)</a>, relative <a id="nutation" data-tip="1213" target="_blank" href="/glossary-term/nutation" class="glossary">nutation</a> of the sacrum, and extension of the spine may contribute to an <a href="https://brookbushinstitute.com/video/overhead-squat-assessment-15-sign-clusters-asymmetrical-weight-shift" target="_blank" rel="noopener">asymmetrical weight shift</a> and <a href="https://brookbushinstitute.com/video/overhead-squat-assessment-9-anterior-pelvic-tilt-excessive-lordosis" target="_blank" rel="noopener">excessive lordosis (</a><a id="anterior" data-tip="1566" target="_blank" href="/glossary-term/anterior" class="glossary">anterior</a> pelvic tilt), and downward rotation of the scapula may contribute to <a href="https://brookbushinstitute.com/video/overhead-squat-assessment-11-shoulders-elevate" target="_blank" rel="noopener">shoulders elevate</a>. Note, despite the inclusion of the rhomboids and splenii in the DLS, and the potential contribution to <a href="https://brookbushinstitute.com/video/overhead-squat-assessment-11-shoulders-elevate" target="_blank" rel="noopener">shoulders elevate</a>, addressing the DLS in those exhibiting <a href="https://brookbushinstitute.com/courses/upper-body-dysfunction-ubd" target="_blank" rel="noopener"> Upper Body Dysfunction (UBD) </a> does not yield significant results. The BI recommends that DLS issues are considered a &quot;less likely&quot; potential contributor if addressing <a href="https://brookbushinstitute.com/courses/upper-body-dysfunction-ubd" target="_blank" rel="noopener"> UBD </a> is the intent.
<h3> Core Exercise: </h3>
As mentioned above, the muscles of the DLS have a propensity to become over-active. It is recommended that over-active muscles are <a id="release" data-tip="1253" target="_blank" href="/glossary-term/release" class="glossary">released</a> and targeting these muscles with strengthening exercise is avoided. There is some evidence to <a id="base-of-support" data-tip="1197" target="_blank" href="/glossary-term/base-of-support" class="glossary">support</a> that <a id="synergistic-dominance" data-tip="1645" target="_blank" href="/glossary-term/synergistic-dominance" class="glossary">over-active synergist</a> strength and function will improve more with exercise that attempts to correct alignment and targets commonly under-active muscles, when compared to exercise that specifically targets <a id="synergistic-dominance" data-tip="1647" target="_blank" href="/glossary-term/synergistic-dominance" class="glossary">over-active synergists</a> (118-122). <a id="specificity" data-tip="1224" target="_blank" href="/glossary-term/specificity" class="glossary">Specific</a> to the DLS, this may imply that exercise that targets the <a href="https://brookbushinstitute.com/courses/erector-spinae" target="_blank" rel="noopener">lumbar extensors</a>, <a href="https://brookbushinstitute.com/courses/biceps-femoris" target="_blank" rel="noopener"> hamstrings</a>, or fibularis muscles should be avoided. Instead, focus on <a href="https://brookbushinstitute.com/courses/bridge-progression" target="_blank" rel="noopener"> bridges</a>, <a href="https://brookbushinstitute.com/courses/chop-pattern-progression" target="_blank" rel="noopener"> chop progressions</a>, and <a href="https://brookbushinstitute.com/video/single-leg-balance-with-reach-excursion" target="_blank" rel="noopener"> single-leg </a><a id="balance" data-tip="1190" target="_blank" href="/glossary-term/balance" class="glossary">balance</a> which may aid in optimizing <a href="https://brookbushinstitute.com/glossary/lengthtension-relationship/" target="_blank" rel="noopener"> </a><a id="lengthtension-relationship" data-tip="1685" target="_blank" href="/glossary-term/lengthtension-relationship" class="glossary">length/tension</a> relationships, and improving posture
<h3> Integrated Exercise: </h3>
The BI suggests ending rehabilitation, corrective exercise, and movement preparation routines with multi-joint exercise/activities (<a href="https://brookbushinstitute.com/glossary/integration/" target="_blank" rel="noopener">integrated</a> exercise) to reinforce new motor patterns. The BI refines &#x201C; <a href="https://brookbushinstitute.com/glossary/integration/" target="_blank" rel="noopener"> integrated</a> exercise&#x201D; selection with research and theory on subsystems. As mentioned above, the muscles of the DL are over-active and should likely be addressed with <a href="https://brookbushinstitute.com/glossary/release/" target="_blank" rel="noopener">release</a> techniques and avoidance of targeted interventions. That is, the <a href="https://brookbushinstitute.com/glossary/muscle-cell/" target="_blank" rel="noopener">muscle</a> and fascial structures that can be <a id="release" data-tip="1253" target="_blank" href="/glossary-term/release" class="glossary">released</a> are addressed, and exercises that place emphasis on the DLS are avoided until movement quality improves. Exercises that should be avoided:
<ul>
 <li>Lumbar extensions</li>
 <li>Hamstring curls</li>
 <li>Nordic hamstring curls</li>
 <li>Locked-knee or straight-leg deadlifts</li>
 <li>Kettlebell windmills</li>
</ul>
<h3> Instrument Assisted Soft Tissue Mobilization (IASTM) of the DLS: </h3>
Fascia&#x2019;s response to <a id="specificity" data-tip="1224" target="_blank" href="/glossary-term/specificity" class="glossary">specific</a> intervention is complex. Responses may include strain hardening with repetitive or constant <a href="https://brookbushinstitute.com/glossary/tension/" target="_blank" rel="noopener">tension</a>, enhanced <a href="https://brookbushinstitute.com/glossary/glide/" target="_blank" rel="noopener">shear</a> and a reduction in cross-bridging between fascial layers, changes in both <a href="https://brookbushinstitute.com/glossary/muscle-cell/" target="_blank" rel="noopener">muscle</a> <a href="https://brookbushinstitute.com/glossary/tone/" target="_blank" rel="noopener">tone</a> and fibroblast mediated pre-tension (with sustained pressure), and/or altered transmission of the force of multiple muscles acting to stabilize a joint (123-125). As mentioned above, some studies imply that direct pressure may increase thoracolumbar fascia <a id="extensibility-2" data-tip="1308" target="_blank" href="/glossary-term/extensibility-2" class="glossary">extensibility</a>, but stretching may not (13-15). IASTM of this fascial line is common practice, and practitioners report good efficacy; however, further research is needed on this and other fascia-specific techniques to <a id="base-of-support" data-tip="1197" target="_blank" href="/glossary-term/base-of-support" class="glossary">support</a> these clinical findings. The BI recommends attempting fascia-specific techniques for the structures of the DLS; however, since additional research is still in development, special attention should be given to <a id="assessment" data-tip="1478" target="_blank" href="/glossary-term/assessment" class="glossary">assessment</a> and re-assessment.

Practical Application

<h3>Subsystems Summary</h3>
<table>
 <tbody>
 <tr>
 <td width="151"> Subsystem </td>
 <td width="216"> Common Behavior </td>
 <td width="151"> Core </td>
 <td width="133"> <a href="https://brookbushinstitute.com/glossary/integration/" target="_blank" rel="noopener"> Integration </a> </td>
 </tr>
 <tr>
 <td width="151"><a href="https://brookbushinstitute.com/courses/intrinsic-stabilization-subsystem" target="_blank" rel="noopener"> Intrinsic Stabilization Subsystem (ISS)</a>
 
 </td>
 <td width="216">Under-active</td>
 <td width="151"><a href="https://brookbushinstitute.com/courses/transverse-abdominis-activation-quadrupeds-progressions" target="_blank" rel="noopener"> Transverse Abdominis (TVA) Activation </a></td>
 <td width="133">N/A</td>
 </tr>
 <tr>
 <td width="151"><a href="https://brookbushinstitute.com/courses/anterior-oblique-subsystem-aos" target="_blank" rel="noopener"> Anterior Oblique Subsystem (AOS) </a></td>
 <td width="216">Over-active</td>
 <td width="151">
 <a href="https://brookbushinstitute.com/courses/chop-pattern-progressions" target="_blank" style="letter-spacing: 0px;" rel="noopener">Chop Progression</a>
 Avoid: planks, crunches, resisted hip flexion
 </td>
 <td width="133">Legs with Push</td>
 </tr>
 <tr>
 <td width="151"><a href="https://brookbushinstitute.com/courses/posterior-oblique-subsystem-pos" target="_blank" rel="noopener"> Posterior Oblique Subsystem (POS) </a>
 
 
 </td>
 <td width="216">Under-active</td>
 <td width="151"><a href="https://brookbushinstitute.com/courses/chop-pattern-progressions" target="_blank" rel="noopener"> Chop Progression </a> and <a href="https://brookbushinstitute.com/courses/bridge-progression" target="_blank" rel="noopener"> Bridge Progression </a></td>
 <td width="133">Legs with Pull</td>
 </tr>
 <tr>
 <td width="151">Deep Longitudinal Subsystem (DLS)</td>
 <td width="216">Over-active</td>
 <td width="151">Avoid: leg curls, lumbar extensions</td>
 <td width="133">Avoid: straight-leg deadlifts, kettlebell windmills, Nordic curls</td>
 </tr>
 </tbody>
</table>
<h3>Signs of DLS Over-activity</h3>
<ul>
 <li> <a href="https://brookbushinstitute.com/courses/solutions-table-overhead-squat-assessment" target="_blank" rel="noopener"> Overhead Squat </a><a id="assessment" data-tip="1478" target="_blank" href="/glossary-term/assessment" class="glossary">Assessment</a> 
 <ul>
 <li><a href="https://brookbushinstitute.com/video/overhead-squat-assessment-5-feet-turn-out-breakdown/" target="_blank" rel="noopener">Feet Turn Out</a></li>
 <li><a href="https://brookbushinstitute.com/video/overhead-squat-assessment-6-knees-bow-in-breakdown" target="_blank" rel="noopener">Knees Bow In </a></li>
 <li><a href="https://brookbushinstitute.com/video/overhead-squat-assessment-7-knees-bow-out" target="_blank" rel="noopener"> Knees Bow Out </a></li>
 <li><a href="https://brookbushinstitute.com/video/overhead-squat-assessment-9-anterior-pelvic-tilt-excessive-lordosis" target="_blank" rel="noopener"> </a><a id="anterior" data-tip="1566" target="_blank" href="/glossary-term/anterior" class="glossary">Anterior</a> Pelvic Tilt </li>
 <li><a href="https://brookbushinstitute.com/video/overhead-squat-assessment-8-excessive-forward-lean" target="_blank" rel="noopener"></a><a href="https://brookbushinstitute.com/video/overhead-squat-assessment-15-sign-clusters-asymmetrical-weight-shift/" target="_blank" rel="noopener">Asymmetrical Weight Shift</a></li>
 </ul>
 </li>
</ul>
<h3>Practical Application </h3>
<ul>
 <li> <a id="release" data-tip="1249" target="_blank" href="/glossary-term/release" class="glossary">Release</a> (self-administered, vibration, or manual): 
 <ul>
 <li><a href="https://brookbushinstitute.com/courses/lumbar-extensor-flexibility" target="_blank" rel="noopener"> Erector Spinae </a></li>
 <li><a href="https://brookbushinstitute.com/courses/scapular-muscle-flexibility"> Rhomboids </a></li>
 <li>Splenius Capitis and Splenius Cervicis</li>
 <li><a href="https://brookbushinstitute.com/courses/hip-external-rotator-flexibility"> Biceps Femoris </a></li>
 <li><a href="https://brookbushinstitute.com/courses/hip-external-rotator-flexibility"> Adductor magnus </a></li>
 <li><a href="https://brookbushinstitute.com/courses/hip-external-rotator-flexibility"> Piriformis, Obturator internus (and deep rotators) </a></li>
 <li><a href="https://brookbushinstitute.com/courses/lower-leg-flexibility"> Fibularis Longus </a></li>
 </ul>
 <a href="https://brookbushinstitute.com/courses/lower-leg-flexibility"> </a>
 </li>
 <li> Core 
 <ul>
 <li>Avoid exercises that focus on erector spinae, adductor, and/or hamstring strengthening.</li>
 </ul>
 </li>
 <li> <a id="integration" data-tip="1473" target="_blank" href="/glossary-term/integration" class="glossary">Integrated</a> Exercise 
 <ul>
 <li>Avoid straight-legged deadlifts and kettlebell windmills.</li>
 </ul>
 </li>
</ul>
<h3>Additional Courses covering Release Techniques for the DLS</h3>
<ul>
 <li> Manual <a id="release" data-tip="1249" target="_blank" href="/glossary-term/release" class="glossary">Release</a> Courses: 
 <ul>
 <li><a href="https://brookbushinstitute.com/courses/static-manual-release-cervical-muscles-upper-trapezius-levator-scapulae-splenii" target="_blank" rel="noopener"> Static Manual Release: Cervical Muscles Part 1 </a></li>
 <li><a href="https://brookbushinstitute.com/courses/static-manual-release-scapular-muscles-levator-scapulae-upper-trapezius-rhomboids-and-pectoralis-minor" target="_blank" rel="noopener"> Static Manual Release: Scapular Muscles </a></li>
 <li><a href="https://brookbushinstitute.com/courses/static-manual-release-trunk-muscles" target="_blank" rel="noopener"> Static Manual Release: Trunk Muscles </a></li>
 <li><a href="https://brookbushinstitute.com/courses/static-manual-release-hip-external-rotators" target="_blank" rel="noopener"> Static Manual Release: Hip External Rotators </a></li>
 <li><a href="https://brookbushinstitute.com/courses/static-manual-release-lower-leg-muscles" target="_blank" rel="noopener"> Static Manual Release: Lower Leg Muscles </a></li>
 </ul>
 </li>
 <li> Self-administered <a id="release" data-tip="1249" target="_blank" href="/glossary-term/release" class="glossary">Release</a> 
 <ul>
 <li><a href="https://brookbushinstitute.com/courses/scapular-muscle-flexibility" target="_blank" rel="noopener"> Scapular Muscle: </a><a id="release" data-tip="1249" target="_blank" href="/glossary-term/release" class="glossary">Release</a> and Lengthening </li>
 <li><a href="https://brookbushinstitute.com/courses/lumbar-extensor-flexibility" target="_blank" rel="noopener"> Lumbar Extensor: </a><a id="release" data-tip="1249" target="_blank" href="/glossary-term/release" class="glossary">Release</a> and Lengthening </li>
 <li><a href="https://brookbushinstitute.com/courses/hip-external-rotator-flexibility" target="_blank" rel="noopener"> Hip External Rotator: </a><a id="release" data-tip="1249" target="_blank" href="/glossary-term/release" class="glossary">Release</a> and Lengthening </li>
 <li><a href="https://brookbushinstitute.com/courses/lower-leg-flexibility" target="_blank" rel="noopener"> Plantar Flexor and Evertor: </a><a id="release" data-tip="1249" target="_blank" href="/glossary-term/release" class="glossary">Release</a> and Lengthening </li>
 </ul>
 </li>
 <li> Vibration <a id="release" data-tip="1249" target="_blank" href="/glossary-term/release" class="glossary">Release</a> 
 <ul>
 <li><a href="https://brookbushinstitute.com/courses/vibration-release-techniques-upper-body/" target="_blank" rel="noopener"> Vibration </a><a id="release" data-tip="1249" target="_blank" href="/glossary-term/release" class="glossary">Release</a> Techniques: Upper Body </li>
 <li><a href="https://brookbushinstitute.com/courses/vibration-release-technique-lower-body/" target="_blank" rel="noopener"> Vibration </a><a id="release" data-tip="1249" target="_blank" href="/glossary-term/release" class="glossary">Release</a> Techniques: Lower Body</li>
 </ul>
 </li>
</ul>

Best-use and Progressions 

Videos

Biceps Femoris (Self-Administered) Static Release

Biceps Femoris (Self-administered) Dynamic Release Technique

Biceps Femoris Vibration Release

Biceps Femoris Manual Static Release

Bibliography

&copy; 2018 Brent Brookbush
Questions, comments, and criticisms are 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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