Introduction and Definitions

Characteristic Electric Activity of Trigger Points

Nervous System Adaptations

Fibromyalgia and Whiplash Syndrome

Additional Definitions, Observable Phenomenon and Pathobiology

Prevalance

Trama and Pain

Continuous low-load activity

Posture

Eccentric Loading

Myalgia

Chemical Changes Correlated with Trigger Points

Muscle Fiber Dysfunction and Trigger Points

NASM

ACSM

ProCert

AFAA

NCBTMB

CanFitPro

PTAGlobal

ISSA

REPS

REPSI

PACE

YOGA

WITS

AUSactive

CIMSPA

AUSPHYSIO

TPTA

NYPT

AOTA

This course discusses myofascial <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> (<a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a>) and their relationship to <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a>. A comprehensive systematic research review is included in this course discussing the prevalence, <a id="etiology" data-tip="1489" target="_blank" href="/glossary-term/etiology" class="glossary">etiology</a>, observable phenomenon, and pathobiology associated with <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger point</a> development. This course also intends to clarify topics that have been obscured by myth and misinformation, including the definition of <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> and <a id="referred-trigger-point-pain" data-tip="1709" target="_blank" href="/glossary-term/referred-trigger-point-pain" class="glossary">referral pain</a> patterns, the relationship between <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> and continuous low-load stress (including <a id="posture" data-tip="1658" target="_blank" href="/glossary-term/posture" class="glossary">posture</a>), and the observable phenomenon that demonstrate the existence and accessibility of <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a>. Further, this course begins to detail the relationship between <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> and <a id="myofascial-pain-sydrome-mps" data-tip="1140" target="_blank" href="/glossary-term/myofascial-pain-sydrome-mps" class="glossary">myofascial pain syndrome</a>, chronic whiplash syndrome, and <a id="fibromyalgia" data-tip="1135" target="_blank" href="/glossary-term/fibromyalgia" class="glossary">fibromyalgia</a>.&#xA0;
Movement professionals (personal trainers, fitness instructors, physical therapists, athletic trainers, massage therapists, chiropractors, occupational therapists, etc.) should consider this course as introductory, or foundational material for self-administered and manual <a id="release" data-tip="1249" target="_blank" href="/glossary-term/release" class="glossary">release</a> techniques. This course is part of our continued effort to build an <a id="evidence-based-practice" data-tip="1538" target="_blank" href="/glossary-term/evidence-based-practice" class="glossary">evidence-based</a>, <a id="integration" data-tip="1473" target="_blank" href="/glossary-term/integration" class="glossary">integrated</a>, systematic, patient-centered, and outcome-driven approach.&#xA0;
<h3>Additional Courses:</h3>
<ul>
 <li><a href="https://brookbushinstitute.com/courses/trigger-point-assessment-and-palpation">Trigger Point </a><a id="assessment" data-tip="1478" target="_blank" href="/glossary-term/assessment" class="glossary">Assessment</a> and Palpation</li>
</ul>
<h2>Snippets from the Course:</h2>
<h3>Definitions</h3>
<ul>
 <li> <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">Trigger Point</a> - &quot;A hyper-irritable spot in skeletal <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> that is associated with a hypersensitive palpable nodule in a <a id="taut-band" data-tip="1148" target="_blank" href="/glossary-term/taut-band" class="glossary">taut band</a>. The spot is painful on <a id="compression" data-tip="1595" target="_blank" href="/glossary-term/compression" class="glossary">compression</a> and can give rise to characteristic <a id="referred-trigger-point-pain" data-tip="1710" target="_blank" href="/glossary-term/referred-trigger-point-pain" class="glossary">referred pain</a>, referred tenderness, motor dysfunction, and autonomic phenomena (1).&quot;</li>
</ul>
There has been some debate regarding the &quot;existence&quot; of <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> and whether they represent a phenomenon that should be addressed. The debate stems from treating the term &quot;trigger point&quot; as a structural entity, rather than a characteristic set of symptoms as described by the creators of the term. That is, the term &quot;trigger point&quot; is similar to the label &quot;low back pain&quot;, and not the label &quot;herniated nucleus pulposus (HNP)&quot;. The gross majority of opposing views on <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> are based on this common fallacy:
<ul>
 <li>Attack a term, based on the opposition&apos;s perceived definition of that term, rather than the expert&apos;s definition, published work, and/or intent for using the label.</li>
</ul>
<h3>Observable Phenomena Associated with Muscle Fiber Dysfunction: </h3>
<ul>
 <li>Increased <a id="tone" data-tip="1639" target="_blank" href="/glossary-term/tone" class="glossary">tone</a> (over-activity)
 <ul>
 <li>General increase in tissue density</li>
 <li>Resistance to stretch</li>
 <li>Changes in EMG activity</li>
 <li>Changes in <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> spindle activity (H-reflex)</li>
 <li>Twitch response</li>
 </ul>
 </li>
 <li>Taut bands</li>
 <li>Palpable nodules</li>
 <li><a id="myalgia" data-tip="1131" target="_blank" href="/glossary-term/myalgia" class="glossary">Myalgia</a>
 <ul>
 <li>Pain upon deep palpation</li>
 <li>Latent <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> (<a id="latent-trigger-point" data-tip="1134" target="_blank" href="/glossary-term/latent-trigger-point" class="glossary">tender points</a>)</li>
 <li>Active trigger points</li>
 <li>Referral pain</li>
 <li>Diffuse myofascial pain and allodynia</li>
 </ul>
 </li>
 <li>Centralization
 <ul>
 <li>Whiplash syndrome</li>
 <li>Chronic low back pain</li>
 <li>Fibromyalgia syndrome</li>
 </ul>
 </li>
</ul>
Based on clinical observations, many of these phenomena may occur simultaneously. For example, pain on palpation is often associated with a general increase in tissue density and/or taut bands, with or without the presence of <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a>. <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> as defined above, likely represent a significant amount of <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a> that includes maladaptation of the peripheral and central <a id="nervous-system" data-tip="1690" target="_blank" href="/glossary-term/nervous-system" class="glossary">nervous system</a>.

Course Description: Muscle Fiber Dysfunction and Trigger Points

<h2>Definitions:</h2>
<ul>
 <li> <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">Trigger Point</a> - &quot;A hyper-irritable spot in skeletal <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> that is associated with a hypersensitive palpable nodule in a <a id="taut-band" data-tip="1148" target="_blank" href="/glossary-term/taut-band" class="glossary">taut band</a>. The spot is painful on <a id="compression" data-tip="1595" target="_blank" href="/glossary-term/compression" class="glossary">compression</a> and can give rise to characteristic <a id="referred-trigger-point-pain" data-tip="1710" target="_blank" href="/glossary-term/referred-trigger-point-pain" class="glossary">referred pain</a>, referred tenderness, motor dysfunction, and autonomic phenomena (1).&quot;</li>
</ul>
There has been some debate regarding the &quot;existence&quot; of <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> and whether they represent a phenomenon that should be addressed. The debate stems from treating the term &quot;trigger point&quot; as a structural entity, rather than a characteristic set of symptoms as described by the creators of the term. That is, the term &quot;trigger point&quot; is similar to the label &quot;low back pain&quot;, and not the label &quot;herniated nucleus pulposus (HNP)&quot;. The gross majority of opposing views on <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> are based on this common fallacy:
Attack a term, based on the opposition&apos;s perceived definition of that term, rather than the expert&apos;s definition, published work, and/or intent for using the label.
It is accurate to say that a characteristic set of symptoms exist, commonly referred to as a &quot;trigger point&#x201C;. There is a significant amount of evidence to demonstrate the prevalence of this characteristic set of symptoms, and additional research to demonstrate the associated pathobiological changes to the <a id="motor-unit" data-tip="1303" target="_blank" href="/glossary-term/motor-unit" class="glossary">motor unit</a>. Insufficient technology has left some aspects of the pathobiological processes unexplained; however, insufficient technology leaves many questions unanswered in every facet of sports medicine research. Insufficient technology is especially apparent in facets of sports medicine research that involve cellular or molecular processes in living humans.
<h2><img src="https://www.datocms-assets.com/25800/1649652322-pec-major-release.png" title="Pectoralis major tripper point release " alt="Common location of the pectoralis major trigger points"></h2>
Some additional research may aid in defining <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a>. A series of studies by Vechiet et al. confirmed that <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> resulted in a decrease in pain pressure threshold (more pain with less stimulus) and that pain was distinctly not cutaneous (7 - 10). Further, <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> often exhibit characteristic <a id="referred-trigger-point-pain" data-tip="1709" target="_blank" href="/glossary-term/referred-trigger-point-pain" class="glossary">referral pain</a> patterns (1, 2, 4 - 7, 11-13), including burning and tingling that may mimic &quot;nerve pain&quot;, pain in areas associated with other diseases, and may contribute to non-specific pain syndromes, such as low back pain, <a id="fibromyalgia" data-tip="1135" target="_blank" href="/glossary-term/fibromyalgia" class="glossary">fibromyalgia</a> syndrome (FS), and whiplash syndrome (11-15). Two reviews were located that provide evidence that acupuncture points and common <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger point</a> sites may be similar (16, 17). Last, although FS may be associated with <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a>, current research suggests that central sensitization is a key factor distinguishing FS from other types of <a id="myalgia" data-tip="1131" target="_blank" href="/glossary-term/myalgia" class="glossary">myalgia</a> (<a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> pain). These studies refine our definition of <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> by adding that they are acute points of increased <a id="sensitivity" data-tip="1226" target="_blank" href="/glossary-term/sensitivity" class="glossary">sensitivity</a>, that are not cutaneous, may result in <a id="referred-trigger-point-pain" data-tip="1709" target="_blank" href="/glossary-term/referred-trigger-point-pain" class="glossary">referral pain</a> patterns, may mimic other issues, may be similar to acupuncture sites, and may contribute but are distinct from FS.
<a href="https://brookbush.s3.us-east-2.amazonaws.com/wordpress/wp-content/uploads/2019/01/The-expanded-MTrP-hypothesis-reproduced-with-permission-from-Gerwin-RD-Dommerholt-J.png" target="_blank" rel="noopener"><img src="https://www.datocms-assets.com/25800/1649652248-mtrp-hypothesis.png" title="Diagram of the &quot;Integrated Trigger Point Hypothesis&quot; from Dommerholt, J., Bron, C., &amp; Franssen, J. (2006). Myofascial trigger points: an evidence-informed review. Journal of Manual &amp; Manipulative Therapy, 14(4), 203-221." alt="Integrated trigger point hypothesis model"> </a>
Diagram of the &quot;Integrated <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">Trigger Point</a> Hypothesis&quot; - Dommerholt, J., Bron, C., &amp; Franssen, J. (2006). Myofascial trigger points: an evidence-informed review. Journal of Manual &amp; Manipulative Therapy, 14(4), 203-221.
Based on current research and the definition above, it is the assertion of the Brookbush Institute that more attention should be given to how terms related to the <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger point</a> phenomena are &quot;sorted.&quot; Although &quot;sorting&quot; and defining terms may seem like an esoteric activity, it has major implications for how terms are defined, used in practice, and what research implies about them. For example, the term &quot;trigger point&quot; should be categorized in a continuum of the clinically observable phenomenon that are the result of, or correlated with, the pathobiology of <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a>. &quot;Muscle fiber dysfunction,&quot; is a general term used to encompass all commonly noted changes resulting from excessive stress to a <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a>, and the clinically observable phenomena that result from those changes. Further, the term &quot;myalgia&quot; should be viewed as a sub-category of the clinically observable phenomena associated with <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a> that results in the perception of pain. (Summary of terms below)
The term &quot;myofascial pain syndrome (<a id="myofascial-pain-sydrome-mps" data-tip="1141" target="_blank" href="/glossary-term/myofascial-pain-sydrome-mps" class="glossary">MPS</a>)&quot; is used in research, and in this paper when replacing the term <a id="myofascial-pain-sydrome-mps" data-tip="1141" target="_blank" href="/glossary-term/myofascial-pain-sydrome-mps" class="glossary">MPS</a> may misrepresent the findings of a study; however, it is the Brookbush Institute&apos;s opinion that this is similar to calling <a id="anterior" data-tip="1566" target="_blank" href="/glossary-term/anterior" class="glossary">anterior</a> shoulder pain, &quot;shoulder impingement syndrome (SIS)&quot;. Rather than aiding in sorting a defined set of symptoms, it only aids in catastrophizing a common, non-specific set of symptoms related to orthopedic issues. Rather than labeling painful symptoms a syndrome, it is recommended that &quot;myalgia&quot; is a sufficient term for most <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> pain. Conversely, FS is appropriately termed a syndrome, as evidence of central sensitization implies a multi-faceted, chronic condition that must be addressed with an <a id="integration" data-tip="1473" target="_blank" href="/glossary-term/integration" class="glossary">integrated</a> approach to see any resolution of symptoms.
Last, although the term &quot;muscle fiber dysfunction&quot; has been chosen to describe the subject of this course, it is understood that this is a neuromyofascial phenomenon. The human movement system is undoubtedly <a id="holism" data-tip="1463" target="_blank" href="/glossary-term/holism" class="glossary">holistic</a>. However, labeling this phenomenon as &quot;muscle fiber dysfunction&quot; separates the subject matter from information that may explain dysfunction originating from damage to a joint (e.g. arthritis), damage to a <a id="nerve-cell" data-tip="1361" target="_blank" href="/glossary-term/nerve-cell" class="glossary">nerve</a> (e.g. neuropraxia), or damage to the fascia (e.g. fasciitis).
<a href="https://brookbush.s3.us-east-2.amazonaws.com/wordpress/wp-content/uploads/2015/02/Upper-Body-Trigger-Points.jpg" target="_blank" rel="noopener"> <img src="https://brookbush.s3.us-east-2.amazonaws.com/wordpress/wp-content/uploads/2015/02/Upper-Body-Trigger-Points.jpg" alt="Upper body trigger points: &lt;a id=" posterior" data-tip="1565" target="_blank" href="/glossary-term/posterior" class="glossary">Posterior</a> deltoid, upper trapezius and Levator Scapulae&quot; title=&quot;Posterior deltoid, upper trapezius, and levator scapulae trigger points&quot;&gt; Upper Body Trigger points: <a id="posterior" data-tip="1565" target="_blank" href="/glossary-term/posterior" class="glossary">Posterior</a> Deltoid, Upper Trapezius and Levator Scapulae

<h3>Additional Definitions:</h3>
<ul>
 <li>Muscle fiber dysfunction: A general term used to encompass all commonly noted changes resulting from excessive stress to a <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">Muscle fiber</a>, and the clinically observable phenomenon that results from those changes.</li>
 <li> Myalgia: <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">Muscle</a> pain, and/or the sub-category of clinically observable phenomena associated with <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a> that include pain.</li>
 <li> Trigger Point: A hyper-irritable spot in skeletal <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> that is associated with a hypersensitive palpable nodule in a <a id="taut-band" data-tip="1148" target="_blank" href="/glossary-term/taut-band" class="glossary">taut band</a>. The spot is painful on <a id="compression" data-tip="1595" target="_blank" href="/glossary-term/compression" class="glossary">compression</a> and can give rise to characteristic <a id="referred-trigger-point-pain" data-tip="1710" target="_blank" href="/glossary-term/referred-trigger-point-pain" class="glossary">referred pain</a>, referred tenderness, motor dysfunction, and autonomic phenomena (1).&quot;</li>
 <li> Referred (<a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">Trigger Point</a>) Pain: Pain that is generated by a <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">Trigger Point</a>, but is felt in a pattern that includes an area <a id="distal" data-tip="1563" target="_blank" href="/glossary-term/distal" class="glossary">distal</a> to that point. The pattern may be reproduced by stimulation of the original <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">Trigger Point</a>. Note, the distribution of referred <a id="trigger-point" data-tip="1638" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger-point</a> pain is rarely completely congruent with the distribution of a peripheral <a id="nerve-cell" data-tip="1361" target="_blank" href="/glossary-term/nerve-cell" class="glossary">nerve</a> or dermatomal segment.</li>
 <li> Tender Point/Latent Trigger Point: A myofascial <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger point</a> that is not painful at rest, only painful when palpated, and may or may not exhibit a characteristic <a id="referred-trigger-point-pain" data-tip="1709" target="_blank" href="/glossary-term/referred-trigger-point-pain" class="glossary">referral pain</a> pattern when palpated. <a id="latent-trigger-point" data-tip="1133" target="_blank" href="/glossary-term/latent-trigger-point" class="glossary">Latent trigger points</a> do result in an acute point of <a id="sensitivity" data-tip="1226" target="_blank" href="/glossary-term/sensitivity" class="glossary">sensitivity</a>, in a <a id="taut-band" data-tip="1148" target="_blank" href="/glossary-term/taut-band" class="glossary">taut band</a> of <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a>, and may restrict the range of motion (1).</li>
 <li> Taut Band: An endogenous localized contracture within the <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> without activation of the motor endplate (2). Palpation can be used to highlight the difference in tissue <a id="tension" data-tip="1229" target="_blank" href="/glossary-term/tension" class="glossary">tension</a> between a <a id="taut-band" data-tip="1148" target="_blank" href="/glossary-term/taut-band" class="glossary">taut band</a> and the surrounding fibers, by slowly &quot;strumming&quot; a <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> perpendicular to the fiber direction. Taut bands are often described as feeling like a &quot;guitar string wound too tight&quot;.</li>
 <li> Twitch Response: A sudden contraction of fibers within a <a id="taut-band" data-tip="1148" target="_blank" href="/glossary-term/taut-band" class="glossary">taut band</a> when strummed (manually), needled, or compressed with a vibration massage device. The contractions may be observed visually, recorded electromyographically (EMG), or visualized with diagnostic ultrasound (3).</li>
 <li> <a id="myofascial-pain-sydrome-mps" data-tip="1140" target="_blank" href="/glossary-term/myofascial-pain-sydrome-mps" class="glossary">Myofascial Pain Syndrome</a> (<a id="myofascial-pain-sydrome-mps" data-tip="1141" target="_blank" href="/glossary-term/myofascial-pain-sydrome-mps" class="glossary">MPS</a>): Diagnosed pain syndrome that generally includes (4-7):
 <ol>
 <li>Tenderness at points in firm bands of skeletal muscle</li>
 <li>Specific patterns of pain referral associated with each point</li>
 <li>Frequent emotional, <a id="posture" data-tip="1659" target="_blank" href="/glossary-term/posture" class="glossary">postural</a>, and behavioral contributing factors</li>
 <li>Frequent associated symptoms and concomitant diagnoses</li>
 <li>MPS is distinct from fibromyalgia</li>
 </ol>
 </li>
 <li> Fibromyalgia: A loosely defined diagnosis that is associated with widespread pain in combination with tenderness at 11 or more of the 18 <a id="specificity" data-tip="1224" target="_blank" href="/glossary-term/specificity" class="glossary">specific</a> tender point sites. Consideration may also be given to the presence of psychosocial stressors and inflammatory disease in the patient&apos;s history. Newer research suggests that <a id="fibromyalgia" data-tip="1135" target="_blank" href="/glossary-term/fibromyalgia" class="glossary">fibromyalgia</a> may be at least in part due to central sensitization of myofascial pain, often associated with <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> (261 - 271).</li>
</ul>
Below is an attempt to list observable phenomena from least to most severe, or perhaps in association with least to most <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> damage/maladaptation:
<h3> Observable Phenomena Associated with Muscle Fiber Dysfunction: </h3>
<ul>
 <li>Increased <a id="tone" data-tip="1639" target="_blank" href="/glossary-term/tone" class="glossary">tone</a> (over-activity)
 <ul>
 <li>General increase in tissue density</li>
 <li>Resistance to stretch</li>
 <li>Changes in EMG activity</li>
 <li>Changes in <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> spindle activity (H-reflex)</li>
 <li>Twitch response</li>
 </ul>
 </li>
 <li>Taut bands</li>
 <li>Palpable nodules</li>
 <li><a id="myalgia" data-tip="1131" target="_blank" href="/glossary-term/myalgia" class="glossary">Myalgia</a>
 <ul>
 <li>Pain upon deep palpation</li>
 <li>Latent <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> (<a id="latent-trigger-point" data-tip="1134" target="_blank" href="/glossary-term/latent-trigger-point" class="glossary">tender points</a>)</li>
 <li>Active trigger points</li>
 <li>Referral pain</li>
 <li>Diffuse myofascial pain and allodynia</li>
 </ul>
 </li>
 <li>Centralization
 <ul>
 <li>Whiplash syndrome</li>
 <li>Chronic low back pain</li>
 <li>Fibromyalgia syndrome</li>
 </ul>
 </li>
</ul>
Based on clinical observations, many of these phenomena may occur simultaneously. For example, pain on palpation is often associated with a general increase in tissue density and/or taut bands, with or without the presence of <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a>. <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> as defined above, likely represent a significant amount of <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a> that includes maladaptation of the peripheral and central <a id="nervous-system" data-tip="1690" target="_blank" href="/glossary-term/nervous-system" class="glossary">nervous system</a>.
<h3> Pathobiology of Muscle Fiber Dysfunction: </h3>
<ol>
 <li>Excessive Stress
 <ul>
 <li>Acute tissue trauma</li>
 <li>Continuous low-load activity
 <ul>
 <li>Postural dysfunction</li>
 </ul>
 </li>
 <li>Eccentric contractions</li>
 </ul>
 </li>
 <li>Insufficient blood flow
 <ul>
 <li>Capillary restriction (especially during isometric contraction)</li>
 <li>Insufficient recovery (cycling of motor units is insufficient)</li>
 </ul>
 </li>
 <li>Metabolic crisis
 <ul>
 <li>Hypoxia</li>
 <li>Cytochrome c-oxidase deficiency</li>
 <li>Mitochondrial, sarcotubular system, and cell membrane changes</li>
 <li>Moth-eaten fibers and degeneration</li>
 </ul>
 </li>
 <li><a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">Muscle fiber</a> changes
 <ul>
 <li>Taut bands and palpable nodules</li>
 <li>Type I fiber hypertrophy</li>
 <li>Increase in Type IIA fibers</li>
 <li>Increase in transitional fibers</li>
 <li>Preferential loss of Type I and/or Type II motor units</li>
 <li>Infiltration of adipose and/or connective tissue</li>
 </ul>
 </li>
 <li>Chemical change
 <ul>
 <li>Markers of inflammation and pain</li>
 <li>Acidity (pH)</li>
 <li>Excessive Ca2+</li>
 <li>Excessive acetylcholine (ACh)</li>
 </ul>
 </li>
 <li><a id="nervous-system" data-tip="1690" target="_blank" href="/glossary-term/nervous-system" class="glossary">Nervous system</a> adaptation
 <ul>
 <li>Altered reflex sensitivity</li>
 <li>Dorsal horn reorganization</li>
 <li>Hippocampus inhibition</li>
 <li>Autonomic system involvement</li>
 </ul>
 </li>
 <li>Centralization</li>
</ol>
A significant amount of research correlates the pathobiology of <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a> with clinically observable phenomena. Although, it may be possible to highlight a lack of research to correlate a <a id="specificity" data-tip="1224" target="_blank" href="/glossary-term/specificity" class="glossary">specific</a> aspect of the pathobiology of <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a> with a <a id="specificity" data-tip="1224" target="_blank" href="/glossary-term/specificity" class="glossary">specific</a> clinically observable phenomenon when viewed in aggregate the relationship is well supported.
<table>
 <tbody>
 <tr>
 <td>
 Special Note: When referring to <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> I am often challenged by individuals citing the following review:
 <ul>
 <ul>
 <li><a href="https://academic.oup.com/rheumatology/article/54/3/392/1796114" target="_blank" rel="noopener"> Quintner, J. L., Bove, G. M., &amp; Cohen, M. L. (2014). A critical </a><a id="assessment" data-tip="1481" target="_blank" href="/glossary-term/assessment" class="glossary">evaluation</a> of the <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger point</a> phenomenon. Rheumatology, 54 (3), 392-399. </li>
 </ul>
 </ul>
 I generally feel that publicly critiquing other credentialed professionals adds to the culture of &quot;trolling&quot;, and with that in mind, I try to refrain. However, there are certain claims in the industry that are being made, seemingly as part of a &quot;contrarian movement&quot;, which are supported by little more than opinion, fallacies, and the misrepresentation/interpretation of research. This paper falls into that category. The paper is full of biased language, false accusations, logical missteps, and academic dishonesty in the <a id="posture" data-tip="1660" target="_blank" href="/glossary-term/posture" class="glossary">form</a> of egregious errors in the citation. This paper should not have been published, should be retracted, represents a poor job by the editorial staff of Rheumatology, and is a serious breach of professionalism by the authors and editors. Apologies should be demanded. You can read my notes on this review via the link below. Please keep in mind, these notes were not originally compiled with the intent of criticizing the authors. I was reviewing the article and its bibliography for continued work on the outline and annotated bibliography that developed into this article. Rather than the review adding wonderful alternative views, theories, and citations, it proved to be a good example of how bias can destroy objectivity, and it stands as an example of how poor citation can destroy trust in the authors and potentially the journal. I also attempted to contact Rheumatology with my notes in an attempt to have the paper retracted, without ever making these notes public. They did not respond.
 <ul>
 <ul>
 <li><a href="https://brookbushinstitute.com/article/critique-of-a-critical-evaluation-of-the-trigger-point-phenomenon" target="_blank" rel="noopener"> Critique of &quot;A Critical </a><a id="assessment" data-tip="1481" target="_blank" href="/glossary-term/assessment" class="glossary">Evaluation</a> of the <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">Trigger Point</a> Phenomenon&quot; </li>
 </ul>
 </ul>
 </td>
 </tr>
 </tbody>
</table>
<a href="https://brookbush.s3.us-east-2.amazonaws.com/wordpress/wp-content/uploads/2016/04/FHL-and-FDL-2.png" target="_blank" rel="noopener"><img src="https://www.datocms-assets.com/25800/1649652438-fhl-and-dhl-trigger-points.png" title="The FHL and FDL common trigger points" alt="&#xA0;Flexor hallucis longus (FHL) and flexor digitorum longus (FDL) manual release"></a>&#xA0;Flexor Hallucis Longus (FHL) and Flexor Digitorum Longus (FDL) Manual Release

<h3> General Prevalence </h3>
The presence of symptoms related to <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a>, including <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a>, is undoubtedly common. In a Thai study of 2463 individuals, starting with a questionnaire and followed by a clinician exam, 6.3% had symptoms matching <a id="myofascial-pain-sydrome-mps" data-tip="1140" target="_blank" href="/glossary-term/myofascial-pain-sydrome-mps" class="glossary">myofascial pain syndrome</a> (<a id="myofascial-pain-sydrome-mps" data-tip="1141" target="_blank" href="/glossary-term/myofascial-pain-sydrome-mps" class="glossary">MPS</a>) (18). A study by Fleckenstein et al. asked German physicians to estimate the number of patients diagnosed with MPS-related pathologies in their clinics, resulting in an aggregate percentage of 46% &#xB1; 27.4% (19). A smaller study performed by internists practicing in Los Angeles reported 30% of office visits satisfied the criteria for <a id="myofascial-pain-sydrome-mps" data-tip="1141" target="_blank" href="/glossary-term/myofascial-pain-sydrome-mps" class="glossary">MPS</a> (20). Prevalence of jaw and face myofascial pain, over the course of a year, in a group of dental students was 19% (21), and a <a id="cross-sectional-study" data-tip="1422" target="_blank" href="/glossary-term/cross-sectional-study" class="glossary">cross-sectional study</a> on 171 randomly selected women in a threshold country, reported 9% prevalence of jaw and face myofascial pain (22). A study by Han et al. demonstrated that every participant in the group of 4 - 11-year-old children exhibited a decrease in pain pressure threshold (increased <a id="sensitivity" data-tip="1226" target="_blank" href="/glossary-term/sensitivity" class="glossary">sensitivity</a>) at a <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger point</a> site in the brachioradialis when compared to non-trigger point sites (23). This may suggest that the development of <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a> and <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> starts early and progresses over a lifetime. Research has also demonstrated that <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> are more common in individuals who perform repetitive low-level <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> exertions as part of their daily activity, for example, office (desk/computer) workers, musicians, dentists, etc. (24 - 27). These numbers may not seem particularly impressive, but it should be considered that the findings in these studies are not the result of evaluating patients with known musculoskeletal complaints. The studies above are more representative of the prevalence of <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a> in the larger population.
<h3> Joint Pain </h3>
The prevalence of <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> and <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a> increases substantially when <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> are specifically assessed in individuals with musculoskeletal complaints (28 - 32). A study by Bajaj et al. demonstrated a significant increase in <a href="https://brookbushinstitute.com/courses/hip-joint" target="_blank" rel="noopener">hip</a> <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> in those with <a href="https://brookbushinstitute.com/courses/hip-joint" target="_blank" rel="noopener">hip </a>osteoarthritis (OA), an increase in <a href="https://brookbushinstitute.com/courses/knee" target="_blank" rel="noopener">knee</a> <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> in those with <a href="https://brookbushinstitute.com/courses/knee" target="_blank" rel="noopener">knee</a> OA, and a combined prevalence of 57% in OA patients (28). Studies by Bron et al. demonstrated that 100% of patients with <a href="https://brookbushinstitute.com/courses/shoulder-glenohumeral-joint" target="_blank" rel="noopener">shoulder</a> pain exhibited <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a>, with the prevalence of active and <a id="latent-trigger-point" data-tip="1133" target="_blank" href="/glossary-term/latent-trigger-point" class="glossary">latent trigger points</a> varying between muscles of the <a href="https://brookbushinstitute.com/courses/integrated-functional-anatomy-shoulder-glenohumeral-joint" target="_blank" rel="noopener">shoulder</a> and <a href="https://brookbushinstitute.com/courses/sternoclavicular-acromioclavicular-scapulothoracic-joints" target="_blank" rel="noopener">scapula</a> (29). Fernandez-Carnero et al. demonstrated that active <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> were found on the affected side, and <a id="latent-trigger-point" data-tip="1133" target="_blank" href="/glossary-term/latent-trigger-point" class="glossary">latent trigger points</a> found on the unaffected side, of all individuals in a group diagnosed with <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> epicondylitis (30). Weinner et al. demonstrated 96% prevalence of <a id="myofascial-pain-sydrome-mps" data-tip="1141" target="_blank" href="/glossary-term/myofascial-pain-sydrome-mps" class="glossary">MPS</a> symptoms in older adults with chronic non-specific low back pain (31). These studies seem to allude to a near-ubiquitous development of <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a> in conjunction with joint pain/pathology.
<h3> Cervical Pain, Headache and TMJ </h3>
Several studies have noted the prevalence of <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> related to cervical pain, headache, and temporomandibular joint syndrome (TMJ) (33 - 40). Studies by Cerezo-T&#xE9;llez et al. and Mu&#xF1;oz-Mu&#xF1;oz et al. demonstrated an increase in active <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> in those with mechanical and chronic neck pain, including 93.7% of patients exhibiting active <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> in the <a href="https://brookbushinstitute.com/courses/trapezius-muscle" target="_blank" rel="noopener">upper trapezius</a> (33, 34). A study by Sari et al. demonstrated both a difference in distribution and an increase in the number of active <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> in those with cervical radiculopathy, as well as a significant proportion of asymptomatic individuals presenting with <a id="latent-trigger-point" data-tip="1133" target="_blank" href="/glossary-term/latent-trigger-point" class="glossary">latent trigger points</a> (for example, 40.2% of asymptomatic individuals had <a id="latent-trigger-point" data-tip="1133" target="_blank" href="/glossary-term/latent-trigger-point" class="glossary">latent trigger points</a> in the <a href="https://brookbushinstitute.com/courses/trapezius-muscle" target="_blank" rel="noopener">upper trapezius </a> (35). Studies by Fern&#xE1;nez-de-las-Pe&#xF1;as et al., Giamberardino et al. and Calandre et al. demonstrated a relationship between cervical <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> and headaches/migraines (36 - 38). Calandre et al. demonstrated that 93.9% of migraine sufferers exhibit active <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a>, with 74% found in temporal and/or suboccipital areas, and palpation of <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> provoking migraine in 30.6% of patients. (36). Fern&#xE1;ndez-de-las-Pe&#xF1;as demonstrated that <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> in the <a href="https://brookbushinstitute.com/courses/trapezius-muscle" target="_blank" rel="noopener">upper trapezius</a>, sternocleidomastoid, and temporalis muscles were associated with chronic tension-type headaches and that active <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> were associated with greater headache intensity and longer duration when compared to the discovery of <a id="latent-trigger-point" data-tip="1133" target="_blank" href="/glossary-term/latent-trigger-point" class="glossary">latent trigger points</a> (37). Studies by Ardic et al. and Fern&#xE1;denz-de-las-Pe&#xF1;as et al. demonstrate a relationship between TMJ and <a id="myofascial-pain-sydrome-mps" data-tip="1140" target="_blank" href="/glossary-term/myofascial-pain-sydrome-mps" class="glossary">myofascial pain syndrome</a> (<a id="myofascial-pain-sydrome-mps" data-tip="1141" target="_blank" href="/glossary-term/myofascial-pain-sydrome-mps" class="glossary">MPS</a>) (39, 40). Ardic et al. demonstrated 55% of participants with TMJ had <a id="myofascial-pain-sydrome-mps" data-tip="1141" target="_blank" href="/glossary-term/myofascial-pain-sydrome-mps" class="glossary">MPS</a> symptoms (39). Fern&#xE1;denz-de-las-Pe&#xF1;as et al. demonstrated <a id="referred-trigger-point-pain" data-tip="1710" target="_blank" href="/glossary-term/referred-trigger-point-pain" class="glossary">referred pain</a> from the neck contributed to TMJ symptoms, and that TMJ patients exhibited greater pain upon palpation in <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger point</a> locations for the <a id="bilateral" data-tip="1552" target="_blank" href="/glossary-term/bilateral" class="glossary">bilateral</a> temporalis, deep masseter, superficial masseter, sternocleidomastoid, <a href="https://brookbushinstitute.com/courses/trapezius-muscle" target="_blank" rel="noopener">upper trapezius</a>, and suboccipital muscles (40). These studies suggest that the development of <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> often accompanies head and neck issues.
A significant amount of additional research investigating the prevalence of <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> as it relates to individual muscles is covered in the &quot;Static Manual Release&quot; courses. The studies above, and additional research investigating individual muscles, implies that <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> and <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a> are very common and strongly correlated with musculoskeletal pathology. The near-ubiquitous discovery of <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> in those exhibiting musculoskeletal issues may <a id="base-of-support" data-tip="1197" target="_blank" href="/glossary-term/base-of-support" class="glossary">support</a> an alternative <a id="hypothesis" data-tip="1446" target="_blank" href="/glossary-term/hypothesis" class="glossary">hypothesis</a> - <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a> and <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> may be evidence of musculoskeletal maladaptation, and a component of an <a id="integration" data-tip="1473" target="_blank" href="/glossary-term/integration" class="glossary">integrated</a> <a id="model" data-tip="1469" target="_blank" href="/glossary-term/model" class="glossary">model</a> of dysfunction and pathology that would also include components such as altered <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> recruitment, <a id="arthrokinematics" data-tip="1863" target="_blank" href="/glossary-term/arthrokinematics" class="glossary">arthrokinematic</a> stiffness/laxity, fascial dysfunction, inflammation, and pain.
<img src="https://www.datocms-assets.com/25800/1649652587-deskjob.jpg" title="Cervical dysfunction is a common issue for many people who sit at their desk" alt="Neck pain is a common complaint for desk workers">

Prevalence

<h3>Mechanisms of Excessive Stress</h3>
<ul>
 <li>Acute tissue trauma</li>
 <li>Constant low-load activity
 <ul>
 <li>Postural dysfunction</li>
 </ul>
 </li>
 <li>Eccentric contractions</li>
</ul>

Mechanisms of Excessive Stress

<span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;">There is general agreement among clinicians that acute musculoskeletal injury increases the prevalence and severity of symptoms related to <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a> and <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a>. The prevalence of studies noted above seems to imply that injury and <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> are at least correlated (23 - 41). Unfortunately, most of these studies do not relate to acute injury. There is ample evidence (discussed below) of mechanical trauma causing direct injury to the cellular membrane, Ca2+ overload, and necrosis (166); however, these studies do not correlate damage with clinically observable signs. The strongest evidence to date investigating the relationship between <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> and acute trauma are studies investigating the relationship between <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger point</a> prevalence and whiplash syndrome (WS). Studies have demonstrated that early onset of acute hypersensitivity and an increase in the number of <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> are prognostic indicators of recovery at 6 months (77 - 80). One study by Baker et al. reported the prevalence of <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> in 50 WS patients was 77% in the splenius capitis, 62% in the semispinalis capitis, and 52% in the sternocleidomastoid (77). Two interesting studies by Fern&#xE1;ndez-de-las-Pe&#xF1;as et al. demonstrated the treatment of <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a> (manipulation and <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger point</a> therapy) was more effective for WPS patients than conventional therapy (active exercises, electrotherapy, ultrasound therapy, and diathermy) (81, 82). Additional research has demonstrated the effectiveness of exercise for cervical dysfunction (83 - 87), which may suggest the aggregate of these studies should be interpreted as manual therapy more effective than modalities. Last, a study by Gunn et al. demonstrated that patients diagnosed with low-back strain and no <a id="latent-trigger-point" data-tip="1134" target="_blank" href="/glossary-term/latent-trigger-point" class="glossary">tender points</a> were disabled for an average of 6.9 weeks, while those with <a id="latent-trigger-point" data-tip="1134" target="_blank" href="/glossary-term/latent-trigger-point" class="glossary">tender points</a> were disabled for an average of 19.7 weeks (89). Although more research is needed investigating the correlation between clinically observable signs (e.g. <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a>) and acute <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> damage, there is sufficient evidence to consider the relationship. More research is also needed on the sequential pathobiological events that follow acute trauma to aid in understanding pathobiological mechanisms, correlated symptoms, and <a id="optimal" data-tip="1571" target="_blank" href="/glossary-term/optimal" class="glossary">optimal</a> treatment.
<span style="background-color: transparent; font-family: inherit; font-size: inherit; font-style: inherit; font-variant-ligatures: inherit; font-variant-caps: inherit; font-weight: inherit; letter-spacing: 0px;"><img src="https://www.datocms-assets.com/25800/1649652778-knee-pain.jpeg" title="Common site of knee pain" alt="Knee Pain">

Trauma and Pain

The development of non-acute <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a> is thought to be a result of tissue over-load, often resulting from near-continuous low-load activity without sufficient recovery. Several theories have been proposed to explain the chronic development of <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> and <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a>, including the &quot;Energy-crisis&quot;, the &quot;Cinderella Hypothesis&quot; (supported by Henneman&apos;s size principle (46 - 51)), the &quot;Shift Model&quot;, and the &quot;Brussel&apos;s Model&quot;. (1, 42 - 46). These <a id="model" data-tip="1471" target="_blank" href="/glossary-term/model" class="glossary">models</a> are not mutually exclusive, may coexist, and are generally in agreement regarding a set of over-arching &quot;stages&quot;. These stages would include: excessive stress results in insufficient blood flow, creating an energy crisis, resulting in cell damage, resulting in the <a id="release" data-tip="1249" target="_blank" href="/glossary-term/release" class="glossary">release</a> of chemicals and neurotransmitters that may stimulate receptors associated with clinically observable signs (e.g. pain).
Several studies have demonstrated a decrease in blood flow (ischemia) within a <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> during contraction, which is especially pronounced during long-duration isometric contractions (52 - 56). This may include reliance on similar motor units during repetitive tasks, which may represent a &quot;local&quot; isometric contraction that could disrupt <a id="optimal" data-tip="1571" target="_blank" href="/glossary-term/optimal" class="glossary">optimal</a> blood flow for <a id="specificity" data-tip="1224" target="_blank" href="/glossary-term/specificity" class="glossary">specific</a> motor units. Studies have demonstrated either a reliance on a small number of motor units, a reliance on similar motor units with one or more continuously active motor units, a tendency of symptomatic individuals to rely on fewer motor units than asymptomatic individuals, and/or relative hypoxia associated with continuous low-load, long-duration tasks (49 - 56). The reliance on similar motor units is a central tenant of the &quot;Cinderella Hypothesis&quot;; a <a id="hypothesis" data-tip="1446" target="_blank" href="/glossary-term/hypothesis" class="glossary">hypothesis</a> named for motor units that are recruited first and still &quot;working&quot; after other units are no longer active (46). Some studies have challenged the &quot;Cinderella Hypothesis&quot; with evidence of the &quot;cycling&quot; of motor units during long-duration activity, proposing that insufficient rest between periods of activity is a more accurate description of how fibers are overloaded (43, 62-66). Although this is likely an important detail for modeling physiological processes, it likely has little impact on <a id="assessment" data-tip="1478" target="_blank" href="/glossary-term/assessment" class="glossary">assessment</a> and interventions for <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a>. That is, whether continuous activation or insufficient rest between cycles results in hypoxia does not matter to the clinician, as commonly used interventions likely address the resulting dysfunction and are not <a id="specificity" data-tip="1224" target="_blank" href="/glossary-term/specificity" class="glossary">specific</a> enough to address cycling versus isometric occlusion.
Several features of <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> architecture and motor control may contribute to the reliance on a small group of low-threshold, type I fibers for low-load activity. First, low-threshold motor units seem to have different control features (69), almost as if adapted for use during continuous low-load activity to the exclusion of larger motor units. Considering &quot;Henneman&apos;s size principle,&quot; these control features may be related to Henneman&apos;s observation that smaller units are recruited first (46 - 51). It is likely that tissue architecture also contributes. Most type I fibers extend the entire distance from <a id="proximal" data-tip="1564" target="_blank" href="/glossary-term/proximal" class="glossary">proximal</a> to the <a id="distal" data-tip="1563" target="_blank" href="/glossary-term/distal" class="glossary">distal</a> end, have relatively constant cross-sectional areas, and terminate in blunt ending, while type II fibers terminate between fascicles at one end, and the cross&#x2010;sectional area decreases progressively along its length (71, 72). This arrangement would imply that type I fibers are the first &quot;tensioned&quot; during any contraction or length change, as type II fibers would have to rely on a collective increase in <a id="tension" data-tip="1229" target="_blank" href="/glossary-term/tension" class="glossary">tension</a> of the <a id="connective-tissue-cell" data-tip="1368" target="_blank" href="/glossary-term/connective-tissue-cell" class="glossary">connective tissue</a> architecture of a <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> for the transmission of force. Research supports this notion, demonstrating that type I fibers are more resistant to stretch, stretch <a id="tension" data-tip="1229" target="_blank" href="/glossary-term/tension" class="glossary">tension</a> develops faster in type I fibers, and type I fibers demonstrate shortening at the ends while lengthening at the middle during eccentric contraction (73 - 76). Inter-muscular force generation is more random when maximal volitional isometric contraction (MVIC) is less than 20% (60). This may be due in part to a phenomenon observed in a study on frog muscles, demonstrating longitudinal force generated by a <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> was equal to <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> force generation (77). Further research is needed to determine the effect <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> force generation has on the <a id="connective-tissue-cell" data-tip="1368" target="_blank" href="/glossary-term/connective-tissue-cell" class="glossary">connective tissue</a> architecture, and how stiffness of the <a id="connective-tissue-cell" data-tip="1368" target="_blank" href="/glossary-term/connective-tissue-cell" class="glossary">connective tissue</a> architecture would increase <a id="lateral" data-tip="1567" target="_blank" href="/glossary-term/lateral" class="glossary">lateral</a> force transmission to attachments. However, it may be hypothesized that the relatively random force generation at low-loads is partly the result of a loss of force to adjacent in-active (not stiff) fibers, reducing efficiency and resulting in greater strain on low-threshold motor units relative to the force needed for the task. The &quot;Cinderella Hypothesis&quot; and reliance on low-threshold, Type I fibers, may be due in large part to inherent control features and characteristics of tissue architecture.
The development of non-acute <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a> and characteristic symptoms is common, which may have contributed to the amount of research and number of working <a id="model" data-tip="1471" target="_blank" href="/glossary-term/model" class="glossary">models</a> regarding this phenomenon. The research to date suggests that motor control, <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> architecture and blood flow play key roles in the development of <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a> resulting from the continuous low-load activity. The correlation between non-acute <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a> and chronic injuries should be investigated further.
<img src="https://www.datocms-assets.com/25800/1649652884-running.jpg" title="Running - an example of a continuous low-load activity" alt="Running">

Many clinicians, texts, and researchers have referred to a relationship between <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger point</a> development and <a id="posture" data-tip="1658" target="_blank" href="/glossary-term/posture" class="glossary">posture</a> or <a id="posture" data-tip="1659" target="_blank" href="/glossary-term/posture" class="glossary">postural</a> dysfunction. The near-ubiquitous presence of <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> in those with musculoskeletal pathology may be considered evidence of a likely relationship. Further, understanding the impact of constant low-load activity may provide a mechanism of tissue injury, as changes in <a id="posture" data-tip="1658" target="_blank" href="/glossary-term/posture" class="glossary">posture</a> often result in small increases in tissue stress that are persistent. Two studies that provide more direct evidence of a relationship between <a id="posture" data-tip="1658" target="_blank" href="/glossary-term/posture" class="glossary">posture</a> and <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger point</a> development - Hoyle et al. demonstrated <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> developed in just an hour of continuous typing in a &quot;high <a id="posture" data-tip="1659" target="_blank" href="/glossary-term/posture" class="glossary">postural</a> stress position (slouching)&quot; (91), and Fern&#xE1;ndez-de-las-Pe&#xF1;as demonstrated that an increased number of <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> was associated with forward head <a id="posture" data-tip="1658" target="_blank" href="/glossary-term/posture" class="glossary">posture</a> and chronic tension-type headaches (92). Although more research is needed, there is evidence of prevalence/correlation, a reasonable <a id="hypothesis" data-tip="1446" target="_blank" href="/glossary-term/hypothesis" class="glossary">hypothesis</a> regarding the mechanism of <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger point</a> development, and studies demonstrating that stressful <a id="posture" data-tip="1661" target="_blank" href="/glossary-term/posture" class="glossary">postures</a> can result in the development or increased <a id="sensitivity" data-tip="1226" target="_blank" href="/glossary-term/sensitivity" class="glossary">sensitivity</a> of <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a>.
Several studies demonstrate changes in stress and motion associated with <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> that may exacerbate <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a>. Lucas et al. demonstrated that <a id="latent-trigger-point" data-tip="1133" target="_blank" href="/glossary-term/latent-trigger-point" class="glossary">latent trigger points</a> were associated with altered scapular motion during arm elevation (94, 95). Ge et al. demonstrated <a id="latent-trigger-point" data-tip="1133" target="_blank" href="/glossary-term/latent-trigger-point" class="glossary">latent trigger points</a> increased fatigability of the <a href="https://brookbushinstitute.com/courses/trapezius-muscle" target="_blank" rel="noopener">upper trapezius</a> during an isometric contraction (96). Note, these studies also demonstrated that treatment reversed these trends (94 - 96). Further, Maher et al. demonstrated that sitting increased the <a id="glide" data-tip="1817" target="_blank" href="/glossary-term/glide" class="glossary">shear</a> stress modulus on <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> when compared to lying in <a id="prone" data-tip="1561" target="_blank" href="/glossary-term/prone" class="glossary">prone</a> (93). This may be evidence that tissues are sheared and pulled around the hyper-contracted region of a <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger point</a> within a <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a>. These findings are not only evidence that <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> may result in changes that reinforce further <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a>, but the changes noted in scapular motion are similar to the changes noted in those exhibiting signs of <a id="posture" data-tip="1659" target="_blank" href="/glossary-term/posture" class="glossary">postural</a> dysfunction (103 - 106). (See <a href="https://brookbushinstitute.com/courses/upper-body-dysfunction-ubd" target="_blank" rel="noopener"> Upper Body Dysfunction (UBD) </a> for more information)
Three studies discussed below, also imply that the temporal and spatial summation of pain can result in a fairly rapid increase in <a id="sensitivity" data-tip="1226" target="_blank" href="/glossary-term/sensitivity" class="glossary">sensitivity</a> and <a id="dorsal" data-tip="1554" target="_blank" href="/glossary-term/dorsal" class="glossary">dorsal</a> horn re-organization (within a few hours) (262, 263). That is, pain intensity and sensitization are amplified by the proximity to the original site, the rate of the stimuli, and whether the area was already painful. This may allude to a mechanism of pain development in those exhibiting <a id="posture" data-tip="1659" target="_blank" href="/glossary-term/posture" class="glossary">postural</a> dysfunction, as changes in <a id="posture" data-tip="1658" target="_blank" href="/glossary-term/posture" class="glossary">posture</a> are often constant, persistent, and progress over time. Sj&#xF8;gaard et al. provide a great review of the relationship between mental load, computer work, altered motor control patterns, altered <a id="motor-unit" data-tip="1303" target="_blank" href="/glossary-term/motor-unit" class="glossary">motor unit</a> activity, <a id="myalgia" data-tip="1131" target="_blank" href="/glossary-term/myalgia" class="glossary">myalgia</a>, and <a id="muscle-cell" data-tip="1374" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle cell</a> damage (97). These cascades may provide a framework that can be used to investigate the relationship between <a id="posture" data-tip="1658" target="_blank" href="/glossary-term/posture" class="glossary">posture</a>, <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a>, and pain at other body segments (e.g. <a href="https://brookbushinstitute.com/courses/lower-leg-dysfunction" target="_blank" rel="noopener"> Lower Extremity Dysfunction (LED)</a>).
As altered <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> lengths are a tenant of <a id="posture" data-tip="1659" target="_blank" href="/glossary-term/posture" class="glossary">postural</a> dysfunction <a id="model" data-tip="1471" target="_blank" href="/glossary-term/model" class="glossary">models</a>, it is worth mentioning here that there is a relationship between length change/stretch reflex and <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a>. A series of animal studies demonstrate that stretch, via mechanical <a id="tension" data-tip="1229" target="_blank" href="/glossary-term/tension" class="glossary">tension</a> on integrins, may result in the mechanical <a id="release" data-tip="1249" target="_blank" href="/glossary-term/release" class="glossary">release</a> of neurotransmitters and CA2+ (98 - 100). This may alter the activity/excitability of a <a id="muscle-cell" data-tip="1374" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle cell</a>, and/or it may have deleterious effects on the <a id="muscle-cell" data-tip="1374" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle cell</a> via the cascade associated with excessive CA2+ (discussed below). Several studies have also demonstrated a relationship between <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> and the altered stretch reflex. Mense et al. describe a relationship between norepinephrine (NE) and depressed feedback control of <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> length (101), and Shwartz et al. demonstrate this may increase <a id="tone" data-tip="1639" target="_blank" href="/glossary-term/tone" class="glossary">tone</a> by amplifying glutamate-driven excitation (102). Note, several studies have demonstrated an increase in NE associated with active <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> (see below). Ge et al. provide more direct evidence of this relationship, demonstrating that <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> exhibit higher H-reflex (electrically induced stretch reflex) amplitude and lower H-reflex threshold than non-MTrPs respectively, suggesting that <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> spindle afferents may be involved (230).
The correlation (and perhaps <a id="etiology" data-tip="1490" target="_blank" href="/glossary-term/etiology" class="glossary">causation</a>) between <a id="posture" data-tip="1659" target="_blank" href="/glossary-term/posture" class="glossary">postural</a> dysfunction and musculoskeletal pain/injury has been well established. <a id="posture" data-tip="1658" target="_blank" href="/glossary-term/posture" class="glossary">Posture</a> is a source of constant low-load activity, which provides a mechanism for <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger point</a> development. <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">Trigger points</a> have been correlated with changes in motion, fatigability, and control of stretch reflex (length/activity), which appear similar to changes noted in those exhibiting <a id="posture" data-tip="1659" target="_blank" href="/glossary-term/posture" class="glossary">postural</a> dysfunction. Further, research has directly correlated increased <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">Trigger points</a> or the development of <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">Trigger points</a> with stressful <a id="posture" data-tip="1661" target="_blank" href="/glossary-term/posture" class="glossary">postures</a>. Although more research is needed to investigate the nuanced relationships between <a id="posture" data-tip="1659" target="_blank" href="/glossary-term/posture" class="glossary">postural</a> dysfunction, <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a>, and <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">Trigger points</a>, initial evidence suggests a relationship does exist.
<img src="https://www.datocms-assets.com/25800/1644874176-forward-head-posture-fix-discount-3-11-20-pm-3-27-14-pm.jpeg" title="A common dysfunction of forward head position" alt="Forward head position">

Several studies have noted that eccentric loading results in structural changes, chemical changes, altered capacity to generate force and pain (107 - 110), similar to those associated with <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a>. The study by Nie et al. provides <a id="specificity" data-tip="1224" target="_blank" href="/glossary-term/specificity" class="glossary">specific</a> evidence of a link between eccentric loading, <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> damage, and clinically observable signs; demonstrating a relationship between eccentric loading, delayed onset <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> soreness (DOMS), and pressure-induced pain (100). Further, a study by Itoh et al. noted a decrease in pain pressure threshold and the development of taut bands seven days post eccentric exercise (123). Structural changes after eccentric exercise include cytoskeletal disruptions, <a id="z-disk" data-tip="1757" target="_blank" href="/glossary-term/z-disk" class="glossary">Z-disk</a> streaming, <a id="a-band" data-tip="1345" target="_blank" href="/glossary-term/a-band" class="glossary">A-band</a> disorganization, and hyper-contracted regions (101, 102). These hyper-contracted regions may be similar to those noted by Mense et al.; hypothesized to be the physical phenomenon resulting in the palpable nodules associated with <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> (198). The protein &quot;desmin&quot; may be particularly important to <a id="sarcomere" data-tip="1323" target="_blank" href="/glossary-term/sarcomere" class="glossary">sarcomere</a> structure, <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a>, and recovery (103 - 106). Research has demonstrated that one of the earliest measurable events post eccentric exercise (within 15 minutes) is a loss of immunostaining for desmin (103 - 104). This results in a tremendous amount of disorganization of contractile filaments (115). Further, a sharp increase in the desmin-to-actin ratio over the following 72-hours has been noted, which may signal recovery (116). If this disorganization is related to hyper-contracted regions and palpable nodules, the role of desmin in active and <a id="latent-trigger-point" data-tip="1133" target="_blank" href="/glossary-term/latent-trigger-point" class="glossary">latent trigger points</a> may be an interesting area of study. Further consideration may be given to eccentric exercise and the decrease in strength, endurance, fine-motor skills, and increase in peak angle with and without pain (108, 116-118), as this may also highlight expected signs associated with <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a>. Last, chemical changes in the cell may be important to understanding the relationships between <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> damage and clinically observable signs. This may include the leak of intramuscular proteins (e.g., creatine kinase enzymes) into the plasma, the loss of intracellular Ca2+ (excessive intracellular Ca2+ and leakage into the plasma), indicators of inflammation such as mast cell granules, and an increase in detectability of CGRP (109, 121, 122). As discussed below, the chemical changes associated with <a id="myalgia" data-tip="1131" target="_blank" href="/glossary-term/myalgia" class="glossary">myalgia</a> and <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> are very similar to those found after eccentric exercise. In brief, eccentric exercise results in <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> damage and observable signs similar to those noted in association with <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> and may aid in creating a general <a id="model" data-tip="1469" target="_blank" href="/glossary-term/model" class="glossary">model</a> of <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a> and symptom development.
<a href="https://brookbush.s3.us-east-2.amazonaws.com/wordpress/wp-content/uploads/2019/01/mothnadhhp.jpg" target="_blank" rel="noopener"><img src="https://www.datocms-assets.com/25800/1649653324-moth-eaten-fibers.jpg" title="NADH stain of moth-eaten &lt;a id=" muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> fibers&quot; alt=&quot;Staining of moth eaten fibers&quot;&gt; NADH stain of &quot;moth-eaten&quot; <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> fibers.

<h3>Adaptations:</h3>
<ul>
 <li>Reduction in blood flow/Hypoxia
 <ul>
 <li>Signs of metabolic/energy crisis</li>
 <li>Moth-eaten fibers and degeneration</li>
 </ul>
 </li>
 <li><a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">Muscle fiber</a> type proportion change
 <ul>
 <li>Taut bands and palpable nodules</li>
 <li>Type I fiber hypertrophy</li>
 <li>Increase in Type IIA fibers</li>
 <li>Increase in transitional fibers</li>
 <li>Preferential loss of Type I and/or Type II motor units</li>
 <li>Infiltration of adipose and/or connective tissue</li>
 </ul>
 </li>
</ul>
The relationship between repetitive stress, <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> contraction, a reduction in local blood flow, hypoxia, and <a id="myalgia" data-tip="1131" target="_blank" href="/glossary-term/myalgia" class="glossary">myalgia</a> has been well established (52 - 56, 124, 125, 150). It is likely that hypoxia results in metabolic crisis, as evidenced by correlations between <a id="myalgia" data-tip="1131" target="_blank" href="/glossary-term/myalgia" class="glossary">myalgia</a> and the presence of cytochrome c oxidase deficiency (127, 128), excessive ACh at motor endplates (190), and deleterious changes to the <a id="mitochondria" data-tip="1255" target="_blank" href="/glossary-term/mitochondria" class="glossary">mitochondrial</a> and sarcotubular system (126 - 129). Further, a metabolic crisis may also explain the appearance of ragged red fibers and moth-eaten fibers which are indications of structural damage to the cell membrane and <a id="mitochondria" data-tip="1257" target="_blank" href="/glossary-term/mitochondria" class="glossary">mitochondria</a> (109, 129, 136). Metabolic crisis may result in necrosis, which could explain the atrophy associated with chronic injury (125 - 127). Further, studies have noted that fatigue and <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> degeneration are higher from constant low-load activities than intermittent activities (even after 30 minutes of rest) (57, 145, 146), which would be better explained by metabolic crisis than the simple depletion of metabolic substrates.
When these events are chronic they lead to further adaptation that may exacerbate blood flow restriction. Cellular changes associated with <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a> have been correlated with narrowed space between fibers, taut bands, and localized abnormal contraction sites that are hypothesized to cause the palpable nodules associated with <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> (196 - 203). This narrowed space between bands and local over-activity may further increase energy demand and further restrict blood flow. <a id="myalgia" data-tip="1131" target="_blank" href="/glossary-term/myalgia" class="glossary">Myalgia</a> is also associated with type I fiber hypertrophy; however, hypertrophy is paired with a reduction in the capillary to fiber cross-sectional area ratio (125 - 127), which in turn contributes to further hypoxia. The combination of these adaptations may aid in explaining the changes that result in chronic pain and dysfunction.
Metabolic issues may also result in fiber type proportion changes. An increase in type IIA fibers has been associated with <a id="myalgia" data-tip="1131" target="_blank" href="/glossary-term/myalgia" class="glossary">myalgia</a> (128). Research has also demonstrated that hybrid fibers are more common in muscles undergoing significant adaptation to training or injury, which may explain some of the type IIA fiber increase (130 - 136). Studies also show that low-back pain and cervical pain lead to a preferential reduction in type I fibers in some <a href="https://brookbushinstitute.com/courses/erector-spinae" target="_blank" rel="noopener">paraspinal</a> muscles (137 - 139), while the multifidus or <a href="https://brookbushinstitute.com/courses/trapezius-muscle" target="_blank" rel="noopener">upper trapezius</a> exhibit a preferential loss of type II fibers (127, 140 - 143). The potentially opposing findings may represent the attempt of <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> to increase endurance (transition from type IIB/X to IIA) while maintaining strength (transition from type I to type IIA), despite an overall loss of motor units. Or, it may suggest that different muscles adapt differently to dysfunction, for example, a difference may be noted between commonly over-active and under-active muscles. Another interesting maladaptation is some muscles maintain cross-sectional area despite the loss of <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> fibers, implying hypertrophy of the remaining fibers, and/or adipose/connective tissue infiltration (137, 143). Despite significant cellular changes and altered fiber type percentages, cross-sectional areas appear to return to near normal values with longer-term/rehabilitation programs (3 weeks-3 years) (147 - 149). Further study is needed to determine whether early intervention may reduce atrophy and whether intervention may aid in returning normal fiber type proportions.

Myalgia, Metabolic Crisis and Muscle Fiber Changes

<h3>Chemical Changes:</h3>
<ul>
 <li>Markers of inflammation and pain</li>
 <li>Acidity (pH)</li>
 <li>Excessive Ca2+</li>
 <li>Excessive acetylcholine (ACh)</li>
</ul>
Significant chemical changes may contribute to the structural changes noted above, and these chemical changes have been correlated with both excessive stress and observable phenomena. These chemical changes can be broken down into three broad categories for the purposes of explanation; however, the human movement professional should be aware that these processes are happening concurrently and influence one another. An increase in pain and inflammatory markers, including acidity, has been correlated with sensitization or stimulation of nociceptors (140 - 164) and may play a special role in explaining <a id="myalgia" data-tip="1131" target="_blank" href="/glossary-term/myalgia" class="glossary">myalgia</a>. The cascade resulting from excessive Ca2+ may explain atrophy (124 - 152), moth-eaten fibers, and a decrease in the number of motor units associated with chronic <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a>. Last, an increase in acetylcholine (ACh), ACh pooling, and or inhibition of acetylcholinesterase (AChE) (153 - 158) may explain taut bands, palpable nodules, and some of the change in electric activity discussed in the next section. The following paragraphs will discuss these changes in more detail.
<h3>Markers of Inflammation and Pain</h3>
An increase in the presence of chemicals, proteins, and neurotransmitters related to inflammation, pain, and sensitization has been associated with exercise-induced cell damage, <a id="myalgia" data-tip="1131" target="_blank" href="/glossary-term/myalgia" class="glossary">myalgia</a>, and <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> (109, 122, 168 - 189). This includes calcitonin gene-related peptide (CGRP), bradykinin, substance P, <a id="nerve-cell" data-tip="1361" target="_blank" href="/glossary-term/nerve-cell" class="glossary">nerve</a> growth factor (NGF), tumor necrosis factor-&#x3B1; (TNF-a), interleukin-1&#x3B2;, interleukin - 6 (IL-6), Interleukin 8 (IL-8), prostaglandin E2 (PGE2), serotonin (including <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> 5 - HT), glutamate, norepinephrine (NE), N- Acylethanolamines (NAEs) and increased macrophage and phagocyte activity (109, 122, 168 - 188). Many of the newer discoveries have been made possible thanks to the development of a &quot;microdialysis&quot; technique, allowing for the sampling of the chemical environment of <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> cells in real-time (122, 169, 170, 173, 174, 179 - 189). One such study by Olausson et al. identified 48 proteins with at least two-fold concentrations present in those with <a href="https://brookbushinstitute.com/courses/trapezius-muscle" target="_blank" rel="noopener">trapezius</a> <a id="myalgia" data-tip="1131" target="_blank" href="/glossary-term/myalgia" class="glossary">myalgia</a> (187), alluding to the immense potential of this technique to add to our understanding. Although a thorough review of the inflammatory cascade resulting from tissue injury and its role in <a id="myalgia" data-tip="1131" target="_blank" href="/glossary-term/myalgia" class="glossary">myalgia</a> is beyond the scope of this article, the review by Shah et al. is recommended (179). Some key points deserve mention here. The pro-inflammatory chemical mentioned above, such as tumor necrosis factor alpha (TNF-a), Interleukin 1-beta (IL-1&#x3B2;), Interleukin 6 (IL-6), and Interleukin 8 (IL-8) have been shown to induce hypernociception (175). This may explain the increased <a id="sensitivity" data-tip="1226" target="_blank" href="/glossary-term/sensitivity" class="glossary">sensitivity</a> to pressure and pain associated with active <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a>. The study by Shah et al (169) used microdialysis to demonstrate that many of the chemicals listed above are present at active <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> sites, but are not present at <a id="latent-trigger-point" data-tip="1133" target="_blank" href="/glossary-term/latent-trigger-point" class="glossary">latent trigger points</a> sites - demonstrating differentiation (170, 171). A study by Hayashi et al. correlated the up-regulation of NGF receptors with chronically painful taut bands (172), aiding in understanding the development of this palpable phenomenon. Studies by Roatta et al. and Shwarz et al. demonstrated that NE affects <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> spindle activity (102, 178), which may have implications regarding the maladaptive length changes in muscles exhibiting signs of <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger point</a> development and <a id="posture" data-tip="1659" target="_blank" href="/glossary-term/posture" class="glossary">postural</a> dysfunction. Last, a study by Hsieh et al. demonstrated that dry needling positively affected the chemical environment of an identified <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger point</a> in an animal study (188), and Moraska et al. demonstrated positive changes in the chemical environment post-ischemic <a id="compression" data-tip="1595" target="_blank" href="/glossary-term/compression" class="glossary">compression</a> (189). As these studies demonstrate, the ability to investigate chemical changes in the environment of the <a id="muscle-cell" data-tip="1374" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle cell</a> aids in associating the pathobiological processes with observable phenomena and hopefully will aid in optimizing intervention selection in the future.
<h3> Acidity (pH) </h3>
Several studies have noted that an increase in tissue acidity can result in pain, specifically within <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> fibers (205 - 209). The microdialysis study by Shah et al., as well as an older study (1957) on &quot;fibrositic muscles&quot; by Brendstrup et al. have demonstrated that the chemical environment of dysfunctional <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> fibers is acidic (lower pH) (170, 210). Studies have specifically demonstrated that creating an acidic environment may stimulate receptors that result in the perception of pain (205 - 206). Although the perception of pain via an increase in acidity is likely the result of stimulating vallinoid receptors, others have modeled more complex links between acidity and local <a id="myalgia" data-tip="1131" target="_blank" href="/glossary-term/myalgia" class="glossary">myalgia</a> (207 - 209).
<h3>Excessive Calcium Ions (Ca2+)</h3>
One of the earliest found and most consistent findings in research investigating <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a> is an increase in the <a id="release" data-tip="1249" target="_blank" href="/glossary-term/release" class="glossary">release</a> of Ca2+ into the <a id="muscle-cell" data-tip="1374" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle cell</a> (109, 151 - 167). Ca2+ is a second messenger for a range of processes in all muscles, and overload may lead to a cascade of events best summarized by Gissel (152): &quot;If the permeability of the sarcolemma for Ca2+ is increased, the <a id="muscle-cell" data-tip="1374" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle cell</a> may suffer Ca2+overload, defined as an inability to control [Ca2+]c. This could lead to the activation of calpains, resulting in proteolysis of cellular constituents, activation of phospholipase A2(PLA2), affecting membrane integrity, an increased production of reactive oxygen species (ROS), causing lipid peroxidation, and possibly <a id="mitochondria" data-tip="1255" target="_blank" href="/glossary-term/mitochondria" class="glossary">mitochondrial</a> Ca2+ overload, all of which may further worsen the damage in a self&#x2010;reinforcing process.&quot; Evidence of CA2+ overload and the resulting cascade are well supported, and CA2+ overload has been correlated with a range of events including acute trauma, <a id="myalgia" data-tip="1131" target="_blank" href="/glossary-term/myalgia" class="glossary">myalgia</a>, low-load continuous activity, and eccentric contractions (excessive exercise) (151 - 161). As this process may result in significant damage, rupture of the cell membrane, and even necrosis, this process may be a primary contributor to the atrophy, moth-eaten fibers, and decreased number of motor units associated with <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a>.
<h3> Excessive Acetylcholine (ACh) </h3>
Evidence of excessive ACh at motor endplates has been correlated with hypoxia (190). Further, CGRP seems to affect both the production of ACh and potentially inhibit the <a id="release" data-tip="1249" target="_blank" href="/glossary-term/release" class="glossary">release</a> of Acetylcholinesterase (AChE) resulting in excessive pooling at the motor endplate (192, 193). Note, an increase in CGRP has been associated with <a id="myalgia" data-tip="1131" target="_blank" href="/glossary-term/myalgia" class="glossary">myalgia</a> and <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> as mentioned above (170, 175, 176). Several studies have noted the ability of ACh to stimulate nociceptors and pain via purigenic receptors, especially when ACh is leaked from damaged <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> cells (194, 195). Of particular interest, a study by Mense et al. demonstrates an increase in regional ACh results in localized abnormal contraction sites, which are thought to be essential to the formation of the palpable nodule of myofascial <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> (198). See the images below of electron microscopy of localized abnormal contraction sites hypothesized to contribute to the palpable nodule associated with <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a>. This study adds to our current understanding regarding palpable phenomenon which includes studies that have correlated <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a> with narrowed space between fibers, local fiber hypertrophy, and palpable taut bands (198 - 203). Understanding the role excessive ACh plays in <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a> aids in understanding myalgic phenomenon, palpable phenomenon, and electromyographic change discussed below.
<a href="https://brookbush.s3.us-east-2.amazonaws.com/wordpress/wp-content/uploads/2018/11/Trigger-Point-Foci.jpg" target="_blank" rel="noopener"><img src="https://www.datocms-assets.com/25800/1649653567-trigger-point-foci.jpg" title="Lesions of rat skeletal &lt;a id=" muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> after local block of acetylcholinesterase and neuromuscular stimulation&quot; alt=&quot;Lesions of <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> after staining&quot;&gt; Mense, S., Simons, D. G., Hoheisel, U., &amp; Quenzer, B. (2003). Lesions of rat skeletal <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> after local block of acetylcholinesterase and neuromuscular stimulation. Journal of applied physiology, 94(6), 2494-2501.

The characteristic electric activity of <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> is not easily differentiated from &quot;normal endplate noise&quot;, but research does indicate tendencies toward higher amplitude spikes and higher mean activity (210). The difficulty in differentiating the endplate noise associated with <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> and asymptomatic <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> fibers may be the reason why some studies have failed to note a difference (211). It is likely that the false assumptions that endplate noise and spontaneous activity were normal and not considering the prevalence of <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a> and trigger/tender points, resulted in a lack of comparison studies until the mid-1990s (212, 213). Hubbard et al. (1993), first demonstrated spontaneous discharges in the order of 10-50 &#x3BC;V and intermittent high-amplitude discharges (up to 500 &#x3BC;V) in painful <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> that were absent in non-trigger points (214). Since that study, several studies comparing <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> and normal <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> fibers have demonstrated <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> exhibit more high amplitude discharges, more instances of spontaneous electric activity, more instances of <a id="twitch-response" data-tip="1142" target="_blank" href="/glossary-term/twitch-response" class="glossary">twitch response</a>, and significantly higher root mean square activity (214 - 221). The activity and ensuing <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> action may be similar to &quot;cramping contractions or cramp potentials&quot;, sometimes noted by experienced electromyographers (222 - 225).
<table>
 <tbody>
 <tr>
 <td>The number of studies correlating endplate dysfunction with trigger points, and the number of studies either purposefully or coincidentally locating trigger points at the motor endplate, implies that trigger points may be symptoms arising at dysfunctional motor endplates (234). Comparing motor point maps to trigger point maps provides a great visual representation of this trend (232 - 234).
 <ul>
 <li>232. Botter, A., Oprandi, G., Lanfranco, F., Allasia, S., Maffiuletti, N. A., &amp; Minetto, M. A. (2011). Atlas of the <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> motor points for the lower limb: implications for electrical stimulation procedures and electrode positioning. European journal of applied physiology, 111 (10), 2461.</li>
 </ul>
 <ul>
 <li>233. Behringer, M., Franz, A., McCourt, M., &amp; Mester, J. (2014). Motor point map of upper body muscles. European journal of applied physiology, 114 (8), 1605-1617.</li>
 </ul>
 </td>
 </tr>
 </tbody>
</table>
Although some of this activity can be attributed to chemical changes (excessive ACh), Hong et. al noted that <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> are likely the result of an <a id="integration" data-tip="1473" target="_blank" href="/glossary-term/integration" class="glossary">integrated</a> response that includes the spinal cord responding to sensitized <a id="nerve-cell" data-tip="1361" target="_blank" href="/glossary-term/nerve-cell" class="glossary">nerve</a> fibers associated with abnormal endplates (226). Kuan et al. published an eloquent study of this relationship, demonstrating that the amount of endplate noise at a <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger point</a> was highly correlated with the pain pressure threshold (218). Two studies have demonstrated that injection of glutamate (a neurotransmitter associated with pain receptors) induced higher peak pain intensity and increased EMG activity when injected into <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a>, but did not when saline solution was used, or when glutamate was injected into <a id="latent-trigger-point" data-tip="1133" target="_blank" href="/glossary-term/latent-trigger-point" class="glossary">latent trigger points</a> or asymptomatic fibers (227, 228). Two studies by Fricton et al. and Wang et al. demonstrate higher electric activity associated with taut bands and the <a id="twitch-response" data-tip="1142" target="_blank" href="/glossary-term/twitch-response" class="glossary">twitch response</a> associated with <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a>, both being neuromuscular phenomena (219, 226). Another study by Ge et al., demonstrated that <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> exhibit higher H-reflex amplitude and lower H-reflex threshold (electrically induced stretch reflex), than non-MTrPs respectively, suggesting that <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> spindle afferents may be involved in their pathophysiology (230). These studies demonstrate that changes in EMG are likely influenced by changes at the motor endplate, as well as by adaptation from the <a id="nervous-system" data-tip="1690" target="_blank" href="/glossary-term/nervous-system" class="glossary">nervous system</a>.
An interesting study relative to practice: A study by Haung et al., used a trigger point-inducing protocol on rats (contusion followed by 8 weeks of eccentric exercise) and demonstrated that the EMG activity associated with <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> did not resolve in the 12-week follow up (231). This may imply that <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> are unlikely to resolve without intervention.
<a href="https://brookbush.s3.us-east-2.amazonaws.com/wordpress/wp-content/uploads/2019/01/Dorsal-Horn.png" target="_blank" rel="noopener"><img src="https://www.datocms-assets.com/25800/1649653726-dorsal-horn.png" title="An image of the &lt;a id=" dorsal" data-tip="1554" target="_blank" href="/glossary-term/dorsal" class="glossary">Dorsal</a> horn, <a id="anterior" data-tip="1566" target="_blank" href="/glossary-term/anterior" class="glossary">anterior</a> horn, and gray commisure&quot; alt=&quot;Dorsal horn <a id="nerve-cell" data-tip="1770" target="_blank" href="/glossary-term/nerve-cell" class="glossary">nerve</a> routes&quot;&gt; Note: <a id="dorsal" data-tip="1554" target="_blank" href="/glossary-term/dorsal" class="glossary">Dorsal</a> Horn and <a id="posterior" data-tip="1565" target="_blank" href="/glossary-term/posterior" class="glossary">Posterior</a> Horn are synonyms.

<ul>
 <li>Spinal Cord Reflex
 <ul>
 <li>Twitch response</li>
 <li>Increase in <a id="sensitivity" data-tip="1226" target="_blank" href="/glossary-term/sensitivity" class="glossary">sensitivity</a> and activity of <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> at the same segment</li>
 </ul>
 </li>
 <li>Centralization
 <ul>
 <li>Re-organization of <a id="dorsal" data-tip="1554" target="_blank" href="/glossary-term/dorsal" class="glossary">dorsal</a> horn neurons and suppression of hippocampus</li>
 <li>Decrease/increase in <a id="sensitivity" data-tip="1226" target="_blank" href="/glossary-term/sensitivity" class="glossary">sensitivity</a> and activity when <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> from a different segment are addressed.</li>
 <li>Adaptation resulting in referral pain</li>
 </ul>
 </li>
 <li>Autonomic System
 <ul>
 <li>Mental and emotional stress, and relaxation effect <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger point</a> activity and sensitivity</li>
 <li>Painful stimulation of <a id="latent-trigger-point" data-tip="1133" target="_blank" href="/glossary-term/latent-trigger-point" class="glossary">latent trigger points</a> results in sympathetic vasoconstriction</li>
 <li>Phentolamine (epinephrine and norepinephrine <a id="antagonists" data-tip="1705" target="_blank" href="/glossary-term/antagonists" class="glossary">antagonist</a>) decreases <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger point</a> activity</li>
 </ul>
 </li>
</ul>
The paragraphs on &quot;Markers of Inflammation and Pain&quot; and &quot;Characteristic Electric Activity and Trigger Points&quot; alluded to the <a id="integration" data-tip="1473" target="_blank" href="/glossary-term/integration" class="glossary">integrated</a> relationship between the <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a>, the motor endplate, and the <a id="nervous-system" data-tip="1690" target="_blank" href="/glossary-term/nervous-system" class="glossary">nervous system</a>. Additional research demonstrates a relationship between <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a> and neuromuscular reflex at the level of the spinal cord, how the CNS may adapt to <a id="myalgia" data-tip="1131" target="_blank" href="/glossary-term/myalgia" class="glossary">myalgia</a>, and how the autonomic <a id="nervous-system" data-tip="1690" target="_blank" href="/glossary-term/nervous-system" class="glossary">nervous system</a> affects activity and <a id="sensitivity" data-tip="1226" target="_blank" href="/glossary-term/sensitivity" class="glossary">sensitivity</a> of <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> (latent or active).
<h3>Spinal Cord:</h3>
The connection between <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> and the spinal cord has been demonstrated in several studies. A series of animal studies by Hong et al. used a combination of transection and lidocaine blocks to demonstrate that spontaneous electric activity may be produced by the motor endplate alone; however, the <a id="twitch-response" data-tip="1142" target="_blank" href="/glossary-term/twitch-response" class="glossary">twitch response</a> relies on a connection between the <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a> and the spinal cord via a motor <a id="nerve-cell" data-tip="1361" target="_blank" href="/glossary-term/nerve-cell" class="glossary">nerve</a> (235 - 238). Hong et al. also demonstrated that transection of the spinal cord above the level of the tested <a id="nerve-cell" data-tip="1361" target="_blank" href="/glossary-term/nerve-cell" class="glossary">nerve</a> did not abolish the <a id="twitch-response" data-tip="1142" target="_blank" href="/glossary-term/twitch-response" class="glossary">twitch response</a>, implying this response is reflex mediated by the spinal cord, and higher CNS function is not necessary (236). Perhaps the connection these studies imply also aids in explaining why botulinum toxin A reduces electric activity and the increased number of <a id="nerve-cell" data-tip="1361" target="_blank" href="/glossary-term/nerve-cell" class="glossary">nerve</a> sprouts at the motor endplate but is not effective for reducing pain at <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> (239 - 241). For example, it may be hypothesized that botulinum toxin A addresses the local contributors to endplate potentials, but has little or no effect on the <a id="nervous-system" data-tip="1690" target="_blank" href="/glossary-term/nervous-system" class="glossary">nervous system</a> mediated contributors to <a id="myalgia" data-tip="1131" target="_blank" href="/glossary-term/myalgia" class="glossary">myalgia</a>. Additional studies add details to the relationship between the spinal cord and <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a>. Fernandez-Carnero et al. demonstrated glutamate-induced pain of a <a id="distal" data-tip="1563" target="_blank" href="/glossary-term/distal" class="glossary">distal</a> <a id="latent-trigger-point" data-tip="1132" target="_blank" href="/glossary-term/latent-trigger-point" class="glossary">latent trigger point</a> increased electric activity of <a id="latent-trigger-point" data-tip="1133" target="_blank" href="/glossary-term/latent-trigger-point" class="glossary">latent trigger points</a> in a <a id="proximal" data-tip="1564" target="_blank" href="/glossary-term/proximal" class="glossary">proximal</a> <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> at the same segmental level of the spine (<a href="https://brookbushinstitute.com/courses/teres-major" target="_blank" rel="noopener">teres major</a> and extensor carpi radialis) (229). Further, Audette et al. demonstrated that needle stimulation of a <a id="unilateral" data-tip="1551" target="_blank" href="/glossary-term/unilateral" class="glossary">unilateral</a> upper trapezius active <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger point</a> resulted in <a id="bilateral" data-tip="1552" target="_blank" href="/glossary-term/bilateral" class="glossary">bilateral</a> (mirror-image) electromyographic activity (242). Srbely et al. demonstrated the administration of a topical cream at the infraspinatus dermatome increased the pain pressure threshold (decreased <a id="sensitivity" data-tip="1226" target="_blank" href="/glossary-term/sensitivity" class="glossary">sensitivity</a>) of <a href="https://brookbushinstitute.com/courses/infraspinatus-and-teres-minor" target="_blank" rel="noopener">infraspinatus</a> <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> but had no effect on <a href="https://brookbushinstitute.com/courses/gluteus-maximus" target="_blank" rel="noopener">glute</a> <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> (243). In an additional study, Srbely et al. demonstrated that dry needling had an anti-nociceptive effect on <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> related to the same segmental level of the spine (244). These studies may indicate reflexive changes to <a id="dorsal" data-tip="1554" target="_blank" href="/glossary-term/dorsal" class="glossary">dorsal</a> horn neurons resulting in increased/decreased thresholds, or reorganization including unmasking of receptive neurons. All of these studies indicate that stimulating a <a id="twitch-response" data-tip="1142" target="_blank" href="/glossary-term/twitch-response" class="glossary">twitch response</a> and/or pain at a <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger point</a> must involve the <a id="muscle-cell" data-tip="1377" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle fiber</a>, peripheral nerves, and the spinal cord.
<h3>Evidence of Centralization (CNS Adaptation):</h3>
There is a significant amount of evidence to suggest <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> result in centralization. In addition to the pain experience requiring higher CNS functions for perception, studies have demonstrated that affecting one <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger point</a> changes the <a id="sensitivity" data-tip="1226" target="_blank" href="/glossary-term/sensitivity" class="glossary">sensitivity</a> and activity of other <a id="distal" data-tip="1563" target="_blank" href="/glossary-term/distal" class="glossary">distal</a> <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a>. This includes the studies mentioned above by Fernandez-Carnero et al., Audete et al. and Srbely et al (229, 242 - 244) that may or may not require higher CNS functions, and a study by Hsieh et al. in which dry needling of forearm muscles not only decreased <a href="https://brookbushinstitute.com/courses/trapezius-muscle" target="_blank" rel="noopener">trapezius</a> <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>, a significant increase in cervical range of motion was also noted (245). Note, the forearm muscles, <a href="https://brookbushinstitute.com/courses/trapezius-muscle" target="_blank" rel="noopener">trapezius</a> and many of the cervical muscles are not innervated by the same segment. Further, a study by Chou et al. demonstrated that acupuncture to remote sites was capable of reducing endplate noise and pain pressure <a id="sensitivity" data-tip="1226" target="_blank" href="/glossary-term/sensitivity" class="glossary">sensitivity</a> of <a id="distal" data-tip="1563" target="_blank" href="/glossary-term/distal" class="glossary">distal</a> <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> (254).
<a id="referred-trigger-point-pain" data-tip="1709" target="_blank" href="/glossary-term/referred-trigger-point-pain" class="glossary">Referral pain</a> patterns also allude to the involvement of the CNS in <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a>. A study by Wang et al. demonstrated that injecting glutamate into a <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger point</a> increased the area of pressure induced pain (246). The increase in the area must be the result of <a id="nervous-system" data-tip="1690" target="_blank" href="/glossary-term/nervous-system" class="glossary">nervous system</a> adaptations increasing the <a id="sensitivity" data-tip="1226" target="_blank" href="/glossary-term/sensitivity" class="glossary">sensitivity</a> of additional afferents. Studies by Hoheisel et al. and Niddam et al. suggest that the <a id="nervous-system" data-tip="1690" target="_blank" href="/glossary-term/nervous-system" class="glossary">nervous system</a> accomplishes this adaptation by reorganizing <a id="dorsal" data-tip="1554" target="_blank" href="/glossary-term/dorsal" class="glossary">dorsal</a> horn neurons (including unmasking of receptive neurons) and suppressing the activity of the hippocampus (247 - 249). Graven-Nielsen et al. demonstrated that experimental <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> pain is influenced by temporal and spatial summation, and Hoheisel et al. and Meng et al. demonstrated <a id="dorsal" data-tip="1554" target="_blank" href="/glossary-term/dorsal" class="glossary">dorsal</a> horn reorganization (within a few hours) (110, 247, 248, 249). Additionally, Gibson et al. demonstrated that <a id="sensitivity" data-tip="1226" target="_blank" href="/glossary-term/sensitivity" class="glossary">sensitivity</a> and the area of pressure induced pain, increased more when <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> were injected after a delayed onset <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> soreness (DOMS) inducing protocol (252). These studies may have important implications for long-duration, low-load excessive stressors, in which a painful stimulus is repeated often, for long duration, and may continue to increase after the initial onset of pain. In a study with significant practical implications, Rubin et al. demonstrated that continued stimulation of a myalgic point resulted in continued propagation of the <a id="referred-trigger-point-pain" data-tip="1709" target="_blank" href="/glossary-term/referred-trigger-point-pain" class="glossary">Referral pain</a> pattern, but that anesthetizing the original site of pain reduced both <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger point</a> pain and <a id="referred-trigger-point-pain" data-tip="1709" target="_blank" href="/glossary-term/referred-trigger-point-pain" class="glossary">Referral pain</a> in parallel (in most cases) (253). These studies suggest that a painful stimulus (<a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger point</a>), especially when initiated in addition to other painful experiences and/or initiated often, may result in brain and spinal cord adaptations that increase the painful area and <a id="sensitivity" data-tip="1226" target="_blank" href="/glossary-term/sensitivity" class="glossary">sensitivity</a>.
<h3>Autonomic Nervous System and Trigger Points</h3>
The effect of breathing, emotional stress, mental stress, and other phenomena, suggest the autonomic system may influence, and be influenced by, <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> and <a id="myalgia" data-tip="1131" target="_blank" href="/glossary-term/myalgia" class="glossary">myalgia</a>. Ge et al. demonstrated that the pain pressure threshold was higher at active <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> when patients were asked to take and hold a deep breath when compared to normal respiration (83). Studies by Lewis et al. and McNulty et al. demonstrated that EMG activity of <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> increased with emotional and mental stress (255, 256), and Banks et al. demonstrated that relaxation training reduced <a id="sensitivity" data-tip="1226" target="_blank" href="/glossary-term/sensitivity" class="glossary">sensitivity</a> of active <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> (257). Zhang et al. and Abbaszadeh-Amirdehi et al. demonstrated attenuated skin blood flow response after painful stimulation of <a id="latent-trigger-point" data-tip="1133" target="_blank" href="/glossary-term/latent-trigger-point" class="glossary">latent trigger points</a> when compared to non-trigger points, suggesting an increase in sympathetic <a href="https://www.sciencedirect.com/topics/medicine-and-dentistry/vasoconstriction" target="_blank" rel="noopener">vasoconstriction </a> (258, 259). Further, phentolamine injection, epinephrine, and norepinephrine <a id="antagonists" data-tip="1705" target="_blank" href="/glossary-term/antagonists" class="glossary">antagonist</a> reduced spontaneous electric activity from <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> (260). The body of research investigating spinal cord reflex, CNS adaptation, and autonomic <a id="nervous-system" data-tip="1690" target="_blank" href="/glossary-term/nervous-system" class="glossary">nervous system</a> involvement demonstrate the <a id="integration" data-tip="1472" target="_blank" href="/glossary-term/integration" class="glossary">integration</a> between <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a> and the <a id="nervous-system" data-tip="1690" target="_blank" href="/glossary-term/nervous-system" class="glossary">nervous system</a> and furthers the <a id="holism" data-tip="1463" target="_blank" href="/glossary-term/holism" class="glossary">holistic</a> nature of the human movement system.

<a id="fibromyalgia" data-tip="1135" target="_blank" href="/glossary-term/fibromyalgia" class="glossary">Fibromyalgia</a> syndrome (FS) and whiplash syndrome (WS) deserve their own courses and individual literature reviews; however, a brief summary of their relationship to <a id="myalgia" data-tip="1131" target="_blank" href="/glossary-term/myalgia" class="glossary">myalgia</a> and <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> is given here. Although FS is a chronic condition of insidious onset, and WS syndrome is a chronic condition of traumatic onset, the perpetuating chronic pain that is common to both conditions may be related to centralization of <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger point</a> pain and reinforcement from active <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a>.
Bennet et al. notes, &quot;Central sensitization has to have an initial genesis, and nociceptive stimuli from painful foci in <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> are increasingly recognized as being <a id="relevance" data-tip="1505" target="_blank" href="/glossary-term/relevance" class="glossary">relevant</a> to the development of fibromyalgia&quot; (261). Based on <a id="relevance" data-tip="1505" target="_blank" href="/glossary-term/relevance" class="glossary">relevant</a> research, it seems likely that the &quot;painful foci&quot; are active <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a>. Ge et al. demonstrated that FS patients exhibited increased <a id="sensitivity" data-tip="1226" target="_blank" href="/glossary-term/sensitivity" class="glossary">sensitivity</a>, more <a id="bilateral" data-tip="1552" target="_blank" href="/glossary-term/bilateral" class="glossary">bilateral</a> <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a>, and more <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> overall when compared to healthy controls (264). Further, Alonso-Blonco et al. and Ge et al. demonstrated that the widespread spontaneous pain pattern in FS may be reproduced by the stimulation of active <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> and summation of their painful regions (262, 263). Widespread pain and testing positive for 11 of 18 common active <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> has a <a id="sensitivity" data-tip="1226" target="_blank" href="/glossary-term/sensitivity" class="glossary">sensitivity</a> of 88.4% and a <a id="specificity" data-tip="1223" target="_blank" href="/glossary-term/specificity" class="glossary">specificity</a> of 81.1% for the diagnosis of FS (266). All of these studies allude to the strong correlation between <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> and FS development.
The inclusion of both <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> and widespread pain in the diagnosis of FS, alludes to the <a id="relevance" data-tip="1504" target="_blank" href="/glossary-term/relevance" class="glossary">relevance</a> of <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> and central sensitization. This does create diagnostic issues, as further testing may be necessary to differentiate FS from <a id="myofascial-pain-sydrome-mps" data-tip="1140" target="_blank" href="/glossary-term/myofascial-pain-sydrome-mps" class="glossary">myofascial pain syndrome</a> (<a id="myofascial-pain-sydrome-mps" data-tip="1141" target="_blank" href="/glossary-term/myofascial-pain-sydrome-mps" class="glossary">MPS</a>). These difficulties may be anticipated based on the studies mentioned above that demonstrate painful states and stress (as noted in <a id="myofascial-pain-sydrome-mps" data-tip="1141" target="_blank" href="/glossary-term/myofascial-pain-sydrome-mps" class="glossary">MPS</a>) which are likely to increase <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> and EMG activity (228, 252, 255, 256, 266, 267). Factors alluding to centralization that may aid in differentiating FS from <a id="myofascial-pain-sydrome-mps" data-tip="1141" target="_blank" href="/glossary-term/myofascial-pain-sydrome-mps" class="glossary">MPS</a> include the &quot;wind-up sensation&quot; (increase in pain with repeated stimulus) and decreased withdrawal reflex threshold (265, 268). The &quot;wind-up sensation&quot; has been correlated with FS and not <a id="myofascial-pain-sydrome-mps" data-tip="1141" target="_blank" href="/glossary-term/myofascial-pain-sydrome-mps" class="glossary">MPS</a> (268), and seems to allude to the temporal summation and sensitization discussed above under &quot;Centralization and Trigger Points&quot; (250, 251). Additionally, Banic et al. demonstrated decreased stimulation threshold for the withdrawal reflex in those individuals diagnosed with FS and WS (265). These centralized factors may be an effective method for differentiating FS from <a id="myofascial-pain-sydrome-mps" data-tip="1141" target="_blank" href="/glossary-term/myofascial-pain-sydrome-mps" class="glossary">MPS</a>. Further research is needed to better understand centralized pain, and create better diagnostic criteria for FS.
The prevalence of <a id="myalgia" data-tip="1131" target="_blank" href="/glossary-term/myalgia" class="glossary">myalgia</a> complaints by those diagnosed with whiplash syndrome (WS) is high; roughly 80% according to a study by Schuller et al (272). Further, WS has been correlated with an increase in cervical <a id="muscle-cell" data-tip="1781" target="_blank" href="/glossary-term/muscle-cell" class="glossary">muscle</a> activity and a loss of range of motion (ROM), and if these changes persist the likelihood of full recovery is reduced (273, 274). These changes are signs of <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a>, but further research also suggests <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger point</a> involvement (79). Several studies have noted that increased sensitization is a feature of WS, especially in those with moderate to severe symptoms at onset, and is correlated with the persistence of symptoms in those who do not fully recover by 6 months (79, 265, 275). This includes the study by Banic et al. mentioned above, that demonstrated that WS and FS patients exhibited a decreased threshold for the withdrawal reflex (209). Further research is needed to investigate whether the myalgic area described by patients with WS can be mimicked by summating the area of active <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> and their <a id="referred-trigger-point-pain" data-tip="1709" target="_blank" href="/glossary-term/referred-trigger-point-pain" class="glossary">referral pain</a> patterns, as was noted in FS. A study by Sterling et al. demonstrated the persistence of WS symptoms were correlated with greater psychological distress (276), which may be similar to the effect mental and emotional changes have on <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> (228, 252, 255, 256, 266, 267). Although the onset of WS is different than FS, and the research on each condition has focused on different factors, the similarities are worth investigating in pursuit of <a id="optimal" data-tip="1571" target="_blank" href="/glossary-term/optimal" class="glossary">optimal</a> treatment options for chronic centralized pain.
The study mentioned above by Rubin et al., demonstrated that treatment of <a id="referred-trigger-point-pain" data-tip="1709" target="_blank" href="/glossary-term/referred-trigger-point-pain" class="glossary">referral pain</a> may not be necessary, as <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger point</a> injection reduced <a id="referred-trigger-point-pain" data-tip="1709" target="_blank" href="/glossary-term/referred-trigger-point-pain" class="glossary">referral pain</a> in parallel (253). Similar findings have been noted relative for fibromyalgia; Staud et al. and Giamberardino et al. demonstrated that <a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger point</a> injection was also effective for reducing overall <a id="fibromyalgia" data-tip="1135" target="_blank" href="/glossary-term/fibromyalgia" class="glossary">fibromyalgia</a> pain, including secondary heat hyperalgesia (268 - 270). Note, Staud et al. emphasized that focus should be placed on active <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> and not necessarily <a id="latent-trigger-point" data-tip="1134" target="_blank" href="/glossary-term/latent-trigger-point" class="glossary">tender points</a> (269). Manual treatment of <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> (in conjunction with cervical manipulation) has also been shown to produce better outcomes than modalities for WS (80, 81). Although centralization alludes to the difficulty in reducing symptoms long-term, these studies may provide some hope that continued treatment of <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> will reduce the painful stimulus and eventually reverse the adaptations resulting in centralized pain.
These studies provide additional insight into the interaction between the <a id="nervous-system" data-tip="1690" target="_blank" href="/glossary-term/nervous-system" class="glossary">nervous system</a> and <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a>, but demonstrate that <a id="fibromyalgia" data-tip="1135" target="_blank" href="/glossary-term/fibromyalgia" class="glossary">fibromyalgia</a> and WS are strongly correlated with <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> and an increase in centralized characteristics. These studies also allude to a strong correlation between <a id="fibromyalgia" data-tip="1135" target="_blank" href="/glossary-term/fibromyalgia" class="glossary">fibromyalgia</a> and WS, active <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a>, centralization, and the treatment of <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a> as a means of reversing the perpetual cycle of centralizing pain. Further research is needed, but it seems a <a id="hypothesis" data-tip="1446" target="_blank" href="/glossary-term/hypothesis" class="glossary">hypothesis</a> may be generated that suggests the <a id="etiology" data-tip="1489" target="_blank" href="/glossary-term/etiology" class="glossary">etiology</a> of <a id="fibromyalgia" data-tip="1135" target="_blank" href="/glossary-term/fibromyalgia" class="glossary">fibromyalgia</a> and WS is a continuum that results from untreated/un-addressed stressors, resulting in <a id="muscle-fiber-dysfunction" data-tip="1126" target="_blank" href="/glossary-term/muscle-fiber-dysfunction" class="glossary">muscle fiber dysfunction</a>, resulting in active <a id="trigger-point" data-tip="1634" target="_blank" href="/glossary-term/trigger-point" class="glossary">trigger points</a>, resulting in centralization, amplified by further physical, emotional or mental stress over time.
<img src="https://www.datocms-assets.com/25800/1649653861-fibromyalgia.png" title="Common trigger points for individuals with fibromyalgia syndrome" alt="Trigger points associated with fibromyalgia">
The 18 points associated with <a id="fibromyalgia" data-tip="1135" target="_blank" href="/glossary-term/fibromyalgia" class="glossary">Fibromyalgia</a> Syndrome Diagnosis - By Sav vas, Jmarchn - Own work, based on: https://commons.wikimedia.org/wiki/File:Tender_points_fibromyalgia.gif, CC0, https://commons.wikimedia.org/w/index.php?curid=21328615

<ul>
 <li><a href="https://brookbushinstitute.com/courses/trigger-point-assessment-and-palpation" target="_blank" rel="noopener"> </a><a id="trigger-point" data-tip="1632" target="_blank" href="/glossary-term/trigger-point" class="glossary">Trigger Point</a> <a id="assessment" data-tip="1478" target="_blank" href="/glossary-term/assessment" class="glossary">Assessment</a> (and Palpation) </li>
 <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-suboccipitals-sternocleidomastoid-scm-scalenes-and-deep-cervical-extensors-multifidi" target="_blank" rel="noopener"> Static Manual Release: Cervical Muscles Part 2 </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-shoulder-muscles" target="_blank" rel="noopener"> Static Manual Release: Shoulder 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-flexors" target="_blank" rel="noopener"> Static Manual Release: Hip Flexors </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-hip-internal-rotators" target="_blank" rel="noopener"> Static Manual Release: Hip Internal Rotators </a></li>
 <li><a href="https://brookbushinstitute.com/courses/static-manual-release-tibia-external-rotators" target="_blank" rel="noopener"> Static Manual Release: Tibia 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>

Additional Courses related to Trigger Points

Bibliography

© 2019 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>

Any Questions, Concerns or Recommendations?

Please contact us through the
Support Page

Legal

Social

Muscle Fiber Dysfunction and Trigger Points

Any Questions, Concerns or Recommendations? Please contact us through the Support Page

Legal

Social

Any Questions, Concerns or Recommendations?

Please contact us through the
Support Page