The Mechanisms of Manual Therapy

Mobilization, manipulation, massage, myofascial release, instrument assisted soft tissue, active release, effleurage, scraping, etc. There are so many types of manual therapy. Each one focused on varying tissues and boasting its own special secret and hidden link to treating dysfunction in the musculoskeletal system. Each one claiming to be that technique, that technique that if only you were proficient at, you could solve ALL the problems for ALL of those stubborn patients who just won’t get better. Some of these techniques were taught to you in school, while some are “higher level” techniques, ones that are even trademarked and only taught to you once you have reached a certain level of “experience”….and paid a certain fee $$$. So many of these techniques are brilliantly marketed. Bells, whistles, bright lights, and mystical words surround these approaches that only that one single or group of gurus can teach. You know, those gurus that are so far beyond the current body of research, clinical knowledge, and experience that only they can teach you the meaning of life.

 

 

 

 

Manual therapy is such an appealing topic and skill set in the world of physical medicine. The ability to lay your hands on someone pain and make them feel better has an incredibly powerful appeal to it. Every one of us in this profession wants nothing more than to help those patients in front of us get out of pain and back to the activities that make their life enjoyable. There is no doubt that there is something special about laying hands on people and the power of human to human contact. The big question lies in what is actually happening during this interaction, and whether or not that technique you are performing is actually doing what you say that it is.

Manipulation: A form of high velocity low amplitude manual thrust technique (often times claimed to be extremely specific to certain joint levels or even sides of specific vertebrae) that most often result in audible joint pops. Many practitioners will claim to be putting vertebrae back into place or resetting pelvises with manipulation/adjustments and popping sounds. The idea that vertebrae can get out of place seems somewhat plausible at face value to the average person. However, under scrutiny from the analytical and scientifically minded this idea is completely ludicrous and has failed to be validated in several research studies evaluating the position of bones pre and post manipulative techniques(further reading can be found hereand here). This idea implies an inherent weakness in the spine that requires constant maintenance therapies and instills a relationship of dependence between patient and practitioner. A scenario that is very good as a business model but very poor as a model that promotes patient independence and confidence to engage in physical activity. Additionally, the idea of palpating these specific malalignments and being specific to manipulating that exact spinal level and side of the spine have been thoroughly debunked as seen here, here and here respectively. Yes, you just read that right. I just said that there is a high likely hood that what you think you just palpated may not be exactly what you think it is…and when you popped it, you may or may not have popped that joint on the side or level you tried to.

 

Myofascial release/ART/IASTM: Myofascial release in one of my personal favorites……to laugh about when I watch videos of John Barnes and his patients writhing around like they took ecstasy and morphine at the same time. Disclaimer- be prepared to be horrified, confused, and amused all at the same time.    

In all seriousness fascia is a very integral part of the human body as it connects, separates, and encapsulates muscles and organs all throughout the body. It is densely innervated and even has contractile smooth muscle like cells spaced throughout to allow for slow and gentle contractions. However, this tissue is EXTREMELY STRONG. So strong in fact, that is has been shown to take up to 925kg of sustained force to deform the plantar fascia and IT band by 1% (reference hereand additional reading hereand here). Needless to say, one can assume that we are most likely not releasing or lengthening fascia with our costly ART certified bare hands or annual fee ASTYM tools.

 

Massage: Massage therapy has a brilliant way of weaving all sorts of claims into their elevator pitch of mechanisms and benefits. Increased blood flow, decrease blood flow when you need it, decreased muscle soreness, increased speed of recovery, break up scar tissue, release fascia, release muscle knots (whatever they are), get rid of toxins (one of my personal favorite BS buzzwords), etc. I won’t go into tons of detail in this section because it has already been so eloquently laid out by Paul Ingraham here at painscience.com. Buuuuut if you don’t want to read his 14,000 words on the topic you can take my word for it and believe all the above stated benefits are dramatically overstated and/or just plain fabricated. This isn't to say that it does nothing, but to say if it does have effects they are much more global and most likely related to the relaxation induced by having another person rub on your muscles in a dark room with lavender scent and the sounds of babbling brooks off in the distance.

 

 

It is quite difficult to back up an argument based on moving anatomy around when it has been well documented in the literature that biomechanical assessment itself is not very reliable at all. For example, palpation for position and movement faults has demonstrated poor reliability here and here suggesting an inability to accurately determine a specific area that may be stiff/out of place and in need of manual therapy. Not to mention the fact that manual techniques have also been shown to lack precision as nerve biased techniques are not specific to a single nerve, joint biased techniques forces are dissipated over a large areas, and different kinetic parameters are observed between clinicians in the performance of the same technique. (references here, here, here, and here)

So by now you are probably sitting there thinking “screw this guy, he’s just raining on my parade and trying to take away my reasoning for every treatment I do on a daily basis”

 

What I hope you’re thinking instead is “if all of the traditional ways I was taught manual therapy aren’t accurate, how in the world does it actually work?” This is a great question, but truthfully is not an easy one to answer with strong confidence.

 

The Mechanisms of Manual Therapy:

In 2009 Bialosky et al. published a study “The mechanisms of manual therapy in the treatment of musculoskeletal pain: a comprehensive model” which proposed several theories to explain how manual therapy most likely actually works to decrease pain, improve ROM, improve function, and decrease perceived stiffness/tightness. Their paper discussed five possible mechanisms, specifically; this model suggests that a mechanical force from manual therapy (any type!!!) can initiate a cascade of neurophysiological responses from the peripheral and central nervous system which are then responsible for the clinical outcomes.

Mechanical Stimulus:

”Collectively, the literature suggests a biomechanical effect of MT; however, lasting structural changes have not been identified, clinicians are unable to reliably identify areas requiring MT, the forces associated with MT are not specific to a given location and vary between clinicians, choice of technique does not seem to affect outcomes, and sign and symptom responses occur in areas separate from the region of application. The effectiveness of MT despite the inconsistencies associate with a purported biomechanical mechanism suggests that additional mechanisms may be pertinent. Subsequently, we suggest, that as illustrated by the model, a mechanical force is necessary to initiate a chain of neurophysiological responses which produce the outcomes associated with MTBased on the current evidence one can hypothesize a potential mechanism of action of manual therapy by altering nociceptive input due to a theoretical sensitivity of peripheral mechanoreceptors.”

 

Neurophysiological Mechanisms:

 “Studies have measured associated responses of hypoalgesia and sympathetic activity following MT to suggest a mechanism of action mediated by the periaquaductal gray (Wright, 1995) and lessening of temporal summation following MT to suggest a mechanism mediated by the dorsal horn of the spinal cord (George et al., 2006) The model makes use of directly measurable associated responses to imply specific neurophysiological mechanisms when direct observations are not possible. The model categorizes neurophysiological mechanisms as those likely originating from a peripheral mechanism, spinal cord mechanisms, and/or supraspinal mechanisms.”

 

Peripheral Mechanisms:

It is well established and accepted that musculoskeletal injuries induce an inflammatory response through histamine, cytokine, and prostaglandin release in tissues which leads to a normal healing process and also influences pain processing via nociceptive input.

“Inflammatory mediators and peripheral nociceptors interact in response to injury and MT may directly affect this process. For example, (Teodorczyk-Injeyan et al., 2006) observed a significant reduction of blood and serum level cytokines in individuals receiving joint biased MT which was not observed in those receiving sham MT or in a control group. Additionally, changes of blood levels of β-endorphin, anandamide, N-palmitoylethanolamide, serotonin, (Degenhardt et al., 2007) and endogenous cannabinoids (McPartland et al., 2005) have been observed following MT. Finally, soft tissue biased MT has been shown to alter acute inflammation in response to exercise (Smith et al., 1994) and substance P levels in individuals with fibromyalgia (Field et al., 2002). Collectively, these studies suggest a potential mechanism of action of MT on musculoskeletal pain mediated by the peripheral nervous system for which mechanistic studies may wish ;to account.”

 

Spinal Mechanisms:

In one of the more traditional models of pain, the gait control theory, ascending stimuli in the spinal cord were thought to override the nociceptive signals in the ALS tract. There is some credence to this theory though it has long been pushed aside in place of much more comprehensive models of neurotags and descending pain models.

However, as stated by bialosky et al. ”MT has been suggested to act as a counter irritant to modulate pain (Boal & Gillette, 2004) and joint biased MT is speculated to “bombard the central nervous system with sensory input from the muscle proprioceptors.” For example, MT is associated with hypoalgesia (George et al., 2006;Mohammadian et al., 2004;Vicenzino et al., 2001), afferent discharge (Colloca et al., 2000;Colloca et al., 2003), motoneuron pool activity (Bulbulian et al., 2002;Dishman & Burke, 2003), and changes in muscle activity (Herzog et al., 1999;Symons et al., 2000) all of which may indirectly implicate a spinal cord mediated effect.

 

Supraspinal Mechanisms:

This section could be an entire blog on its own as there are countless emotional/stress/memory factors that play into the experience of pain and possible ways to decrease pain via manual therapy on the supraspinal level.

“Variables such as placebo, expectation, and psychosocial factors may be pertinent in the mechanisms of MT (Ernst, 2000;Kaptchuk, 2002). For example expectation for the effectiveness of MT is associated with functional outcomes (Kalauokalani et al., 2001) and a recent systematic review of the literature has noted that joint biased MT is associated with improved psychological outcomes (Williams et al., 2007). For this paper we categorize such factors as neurophysiological effects related to supraspinal descending inhibition due to associated changes in the opioid system (Sauro & Greenberg, 2005), dopamine production (Fuente-Fernandez et al., 2006), and central nervous system (Petrovic et al., 2002;Wager et al., 2004;Matre et al., 2006) which have been observed in studies unrelated to MT.”

 

Conclusion:

This is by no means an all-encompassing account of every possible way in which manual therapy can possibly exert an effect and influence pain and healing. Realistically, several of these aspects may play only a very minor role in pain modulation. Additionally, there are likely countless mechanisms in which manual therapy works that we have yet to discover/measure with well designed research studies. As one of my former professors used to say “don’t hear what I’m not saying”. I AM NOT attempting to say that one should no longer use manual therapy in their practice, as it has been shown to be beneficial time and time again. I myself use quite a bit to facilitate patients to engage in more active strategies of rehab. I am however, saying that the biomechanical aspects of manual therapy you were most likely taught and educate your patients on are inaccurate at best and harmful at worst. You could possibly be creating a nocebo effect by portraying the idea of a weak and fragile body that cannot easily withstand the forces of daily life without “getting out of whack”. I encourage you all to attempt to “Cross the Chasm” as Jason Silvernail would say, and re-evaluate why you are doing manual therapy and how it may possibly work.

 

Jarod Hall, PT, DPT, CSCS

Share this post