*Note: This is part of a series of thoughts on the topic of looking at movement and movement related symptoms as influenced by the nervous system. These will be dynamic posts with additional content and references being added as time allows, but the primary purpose of the posts are to share my current thoughts on the influence of manual therapy and exercise on what we see and feel in our patients. I hope others will engage me in these thoughts and provide their perspectives and also criticism into the process.
In part 1, I wanted to provide the definition for post-antalgic patterning which I believe is important to understand before thinking about how we treat it (if it even needs to be treated), for which I lay the ground work here:
Post-Antalgic Patterning – Part 2 – A Quick Reference for Manual Therapy and the Nervous System
A little over a year ago Jason Silvernail released a great video summary on manual therapy and the nervous system called “Crossing the Chasm” which definitely had its intended effect on me. This discussion has been a “hot topic” for at least a decade. As I have attempted to share this same information with other clinicians, I have noted a trend towards wanting more “practical” connection between the techniques we use on a daily basis and the nervous system. As a result, over the last year I have started to formulate a way to bring a little bit of clarity to a very complex topic.
Mechanoreceptors – The elephant in the room
In most of our academic preparatory programs for various rehabilitation disciplines, our afferent and efferent sensory nerve fiber education has focused primarily on severe neurological conditions of the peripheral and central nervous system (stroke, spinal cord injury, CNS disease, etc.). However, when it comes to the role of the nervous system in musculoskeletal conditions, the focus tends to be on nocioception (note of importance: nocioceptors are NOT PAIN RECEPTORS!), chemoreceptors (in particular the relationship to inflammatory mediators), proprioception, muscle spindles, and the golgi tendon reflex. We might touch on some afferents when we talk about gate control, but in general, mechanoreceptors are a very minor part of “most” professional academic programming offerings. This is despite that fact that mechanoreceptors may be one of the bodies most densely dispersed points of interaction with our nervous system, in particularly in the tissues we commonly claim to be treating (joint capsules, fascia, ligaments, muscles, etc.).
I remember vaguely talking about Ruffini Endings, Merkel’s discs, Pacinian and Meisners Corpuscles, but I don’t remember much emphasis on them and I certainly didn’t see any value in even recalling their names at the time. Yet now I realize they are probably some of the most important structures I deal with on a daily basis, in particular when it comes to manual therapy interventions. We get so obsessed with the biomechanical properties of soft tissue and joints and the illusion that we can mechanically alter them through our hands and various tools despite growing evidence that this simply is not the case, or at best, has an extremely small role in the big picture. Yet we choose to ignore, or at the very least downplay, the one basic fundamental pathway, the cascade of neurophysiological events which occur every time skin is compressed. These events can result both in short term and long term tissue and movement quality changes which have the potential to explain every single “change” seen through the use of manual therapy. Furthermore, any inflammatory, fluid dynamics, or thermal responses which potentially could come about from an aggressive intervention could have chemical, thermal, and fluid interactions with mechanoreceptors, chemoreceptors, and thermoreceptors thereby compounding and/or altering an existing externally induced neurological stimulus. If the inflammatory, fluid, or thermal process remains active for hours or days, this could yield a sustained stimulus on mechanoreceptors, thermoreceptors, and chemoreceptors thereby influence the nervous system for an extended period of time (think of a “built-in portal e-stim unit” that already exists in all humans).
Perhaps more important than the external stimulus itself is the ability to modify, enhance, and/or guide the therapeutic outcome of the neurophysiologic response from the stimulus with an educational context provided to the patient, allowing for a profound impact on how they perceive touch and movement.
So what does the pathway for this manual therapy to mechanoreceptor stimulus to tissue quality/movement change look like? Dr. Schleip has perhaps best described this in his work on fascial plasticity, of which this diagram provides perhaps the most concise explanation of the relationship between manual therapy and the nervous system.
To further help solidify the connection between our commonly utilized manual therapy techniques and the nervous system, I put together a couple of acronyms to show the connection between groups of mechanoreceptors and various manual therapy technique:
“RuffMerks need tender care”
- Ruffini Endings (End Organs) & Merkel’s discs are slow adapting mechanoreceptors which respond best to slow sustained and deep tension
- ANS (PNS) & CNS interactions
- General massage, myofascial release techniques, and possibly even ischemic trigger point releases likely preferentially engage these mechanoreceptors
“PacMeisners need action”
- Pacinian and Meisners Corpuscles are fast adapting mechanoreceptors which respond best to fast & vibratory inputs and are key to texture discrimination (think edged/textured tools)
- Predominantly CNS interactions although ANS (PNS) possible
- Greater concentration subcutaneously are also more frequent on the tendinous site
- IASTM style, cross friction (hand or tool), and oscillating techniques likely preferentially engage these mechanoreceptors
- Also thought to play a role in high velocity manipulation
“Free nerve endings do it all”
- Some free nerve endings are intermediate adapting mechanoreceptors and can respond to any form of touch, or any modality (chemical, thermal, electrical) for that matter.
“Ligamentous Mechanoreceptors – I got nothing”
- 4 types, varying adaptability, primarily stretch mediated, although possibly facilitated through touch if the ligament is superficial enough to be compressed
- Engaged primarily with mobilization/manipulation
Last but not least, how can so called “inert” soft tissue, or fascia, have tissue tension or “tonus”?
More regarding the existence of smooth muscle cells within fascia can be found here.
To be continued in part 3..