Tuesday, May 15, 2018

Isometric Muscle Contraction for Immediate Analgesia and the Role of Fascial Innervation and Load. — A review of recent research and treatment implications.

Isometric Muscle Contraction for Immediate Analgesia and the Role of Fascial Innervation and Load.
A review of recent research and treatment implications.

“The data is not enough, even if the data is based on very good science.  It has to be communicated in a way that would really tap into peoples’ needs—their desires.  If people are afraid, we should address that.” -Tali Sharot, Interview (2017)- Hidden Brain,NPR, December 25, 2017.
For the past year or two, fascia has been on my ‘therapy radar,’ thanks in large part to ongoing conversations with Clare Frank, DPT.  These conversations have led me to further explore the role of fascia in the human movement system.  My appreciation for fascia’s role in the kinetic chain has grown considerably.  Before we dive deep into the waters of fascia and its dynamic impact on human movement, I’d like to invite you to answer a few questions related to isometric muscle contractions.  While it may seem off-topic, shortly, you will see how it all works together. 

Are isometric muscle contractions static or dynamic?

Ask me this question a month ago and I would quickly answer, ‘Static.’  How much do you use or prescribe isometric contractions in clinical practice?  Until a few months ago, this question would have garnered a side-eye and shoulder shrug from me, “I don’t know— Not really— I mean, I use isometrics for early tendon loading, or to cue patients in the ‘discovery’ of muscles they never knew existed or have seemingly forgotten.  Why the third degree?” (Why am I growing defensive of my own introspection here?).  To be honest, there has been a lack of rationale in my use of isometrics.  Enter this small RCT by Ebonie Rio, et al1

What is it good for?  Absolutely, SOMETHING!

The use of isometric contractions for analgesia is not a new pain management technique, according to a very brief 'google-scholar' search.  A recent series of studies by Rio et al appear to be the first to associate isometric contractions with tendinopathic pain.1-9 In the aforementioned study, the greatest limitations are perhaps the limited sample size (N of 20; 10 for each arm), and limited supervision of intervention (isometric vs. isotonic muscle contraction), however this should not discredit potential benefits of isometric contractions.
Rio et al discuss several potential benefits of isometric contractions for pain modulation.  At first read, these behavioral and centrally-mediated pain modulating benefits piqued my attention. The authors postulate the following mechanisms by which isometric contractions modulate the pain experience with patellar tendinopathy.  I offer my commentary in blue:
1.   less pain may lead to higher activity intensity or participation in more training sessions (decreased time lost to injury, greater perceived self-efficacy, and active coping mechanisms)
Treatment dominated by passive strategies is less effective than active treatment (i.e., exercise), primarily because passive strategies hinder self-efficacy and reinforce a dependence on external factors, practitioners, modalities (including medications and more invasive, surgical procedures).  This does not dismiss or eliminate the importance or efficacy of manual therapy or soft tissue mobilization/massage.  At the same time, this should serve as a reminder that passive interventions should not be the primary mode of intervention.  Use this as an opportunity to make passive interventions more interactive, teamwork between patient and practitioner.12-13 

2.   removing fear from exercise.
In rehabilitative care, a tool that yields this result is worth its weight in gold.  Fear of exercise and fear of movement are two of the greatest limiting factors in physical therapy care (reducing avoidant behavior and passive coping mechanisms—see associated contextual cues listed in #5 below).

3.   improved self-efficacy in that they (patients) can modulate their own pain (and this is analgesic in itself).

4. improved sense of control, as anxiety, closely linked to low sense of control, has differential and synergistic effects on pain.  
This point might be understated.  Patients seek treatment when they are no longer able to manage or control symptoms independently. Active analgesia via isometric muscle contraction swings the pendulum of control from “absent” to “full” in mere moments. 

5.   contextual cues associated with “active” analgesia imply recovery, health, and capacity, whereas the contextual cues associated with “passive” analgesia, such as ice, imply tissue damage and inflammation… and a perceived frailty or fragility of recovering tissues/structures, that cannot be loaded until tissue restoration is completed.  Pain reduction by loading tissue reinforces the tissue durability.  The human body isn’t that frail.  In recovery and rehabilitation, the body yearns to be loaded, and this accelerates recovery and regeneration.

It makes sense, right?  Considering home exercise adherence can be a major limiting factor to patient outcomes, these effects carry great appeal.  Fear, anxiety and one’s ability to catastrophize are forces to be reckoned with.  
The closest we have to a magic pill, is exercise.  But when exercise is painful, it causes a lack of incentive. or motivation for adherence.  Repeating the mantra, “no pain, no gain,” simply isn’t a solution.  Painful movement discourages activity.  It leads to in-action, and avoidance.  If isometric contractions can reduce pain and reduce fear of movement, that magic pill borders on Lord of the Rings-type .

The Local Tissue Effects of Isometric Muscle Contraction

To a lesser extent, Rio et al discuss several potential implications of isometric contraction on local tissues, including quadriceps muscle architecture, tendon properties, and cortical drive to the quadriceps.10-11 These implications appear, somewhat, as an afterthought. The authors reference a rather archaic (1983) study evaluating the effects of dynamic strength training, not isometrics, changing muscle architecture. This is essentially a comparison of apples and old oranges.10
Only recently did I really begin to consider local tissue implications with isometrics.  During a Movement Links Advanced Skills Course of the shoulder, Clare Frank led a discussion on ‘fascial loading’ and ‘fascial innervation.’  Wait, what’s fascia got to do with it (Hopefully the neuro-tag for Tina Turner’s 1984 hit single was just activated in your brain)?  Fascial loading and innervation, huh?  What role does fascia play in an isometric muscle contraction?  Just what is Fascia, exactly?

Figure 1 Within a muscle cell: A scanning electron micrograph of endomysial structures (fascial tissue) remaining after removal of the myofibrillar contents of muscle cells. From Schleip et al15

There is some debate as to what constitutes fascia versus other types of tissue.  For our purposes, we shall use the term fascia to describe the ‘soft tissue component of the connective tissue system that permeates the human body, fibrous collagenous tissues which are part of a body-wide tensional force transmission system.’14

Fascial Innervation:

Fascia is abundant, providing connections between skin and deeper tissues, surrounding organs and muscles and is interwoven within muscles.  While fascia is an abundant ‘body-wide tensional force transmission system,’ it is also a very powerful sensory organ.  Interestingly, compared with muscular tissue’s innervation with muscle spindles, the fascial network possesses 10x higher quantity of sensory nerve receptors than its red muscular counterpart.16 Have you ever pulled a muscle, or experienced ‘muscle soreness’ after vigorous exercise?  Such bodily complaints are related to both fascia and muscles because stress and strain affect both muscle and fascia. 

Fascial Loading

Traditionally, muscular joint movement was believed to be the result of skeletal muscle shortening (concentric contraction), transferring energy through passive tendons to create joint movement.
17 While this is still true, ‘in human movements such as jumping, walking, and ankle bending, the muscle fiber contracts at a nearly constant length, whereas the tendon performs a stretch-shorten cycle.’ Two studies have demonstrated activities involving counter movement, such as jumping, that ‘The muscles fibers contract in an almost isometric fashion (they stiffen temporarily without any significant change in their length) while the fascial elements function in an elastic way with a movement similar to that of a yo-yo.  It is this lengthening and shortening of the fascial elements that produces the actual movement.17-19 Dynamic, counter movement (jumping) is fundamental to athletic performance in basketball and volleyball, the sports played by the subjects in the Rio et al study previously discussed.

Figure 2 Length changes of fascial elements and muscle fibres in an oscillatory movement with elastic recoil properties (A) and in conventional muscle training (B). The elastic tendinous (or fascial) elements are shown as springs, the myofibers as straight lines above.  Note that during a conventional movement (B) the fascial elements do not change their length significantly while the muscle fibers clearly change their length.  During movements like hopping or jumping, however, the muscle fibers contract almost isometrically while the fascial elements lengthen and shorten like an elastic spring.  In Schleip et al20 and Kawakami et al.19

Consider this notion of fascial innervation in combination with fascial loading.  Fascia is abundant.  It is tough, and very sensitive.  Remember our discussion on the ‘archaic’ Rio et al reference, comparing the apples and oranges of dynamic exercise in a study of isometric exercise?  Considering our discussion on fascial loading and fascial innervation, it appears this “archaic” reference isn’t such an abstract notion.  Ask yourself, ‘Are isometric muscle contractions static or dynamic?’ In light of these concepts, the answer requires a bit more reflection- an isometric muscle contraction yields no net joint movement (static), however, a change in length of fascial elements has been measured and this is a dynamic activity.  Don’t forget the analgesic effects!  Ask me now, ‘Are isometric muscle contractions static or dynamic?’ I will likely answer, ‘yes’ (which doesn’t really answer the question, and still, it does, because it is both static and dynamic) or ‘it depends…’


Blogpost by: Paul Tucker, DPT

Paul Tucker is a physical therapist for Kaiser Permanente in Baldwin Park, a Movement Links certified clinician, and a graduate of Kaiser Permanente's Residency and Fellowship programs. 

1.             Rio, Ebonie, et al. "Isometric contractions Are more analgesic than isotonic contractions for patellar tendon pain: an in-season randomized clinical trial." Clinical Journal of Sport Medicine 27.3 (2017): 253-259.
2.             Rio, Ebonie, et al. "The pain of tendinopathy: physiological or pathophysiological?." Sports medicine 44.1 (2014): 9-23.
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