"There are two “laws” of tissue adaptation, one each for hard and soft tissue. Wolff’s law is that bone will change and strengthen in response to loading. This was first noticed by Julius Wolff in the 19th Century, who got the naming rights. It was greatly refined in the mid 20th century by Dr. Harold Frost, an American surgeon who studied bone biology, and published scientific papers more often than I change my socks. The full details of how bone responds to stress are described in his Mechanostat model. The corollary in soft tissue is the obscure and much less developed Davis’ law. (No one even seems to know who Davis was.)
Although there’s no question soft tissue does adapt to stress, the responses of muscles, tendons, and ligaments are much more complex and less well understood. Many treatments are based on the idea of forcing adaptation or “toughening up” tissues by stressing the tissues. It has always been a reasonable idea, but the devil is in the details: what constitutes the “right” amount and kind of stress is difficult to know, and the results of such therapies have generally been highly inconsistent.
“What doesn’t kill you makes you stronger.” Except, it doesn’t always! We can only adapt to so much stress so quickly — but it’s almost miraculous when we do adapt. How does tissue adaptation work? How good at it are we really? And can it be exploited for a treatment effect? Some popular therapies like Graston Technique and Prolotherapy are based on this idea.
There are two “laws” of tissue adaptation, one each for hard and soft tissue. Wolff’s law is that bone will adapt to loading. This was first noticed by Julius Wolff in the 19th Century, who got the naming rights. It was greatly refined in the mid 20th century by Dr. Harold Frost, an American surgeon who studied bone biology (and published scientific papers more often than I change my socks). The full details of how bone responds to stress are described in his Mechanostat model.
But bone cells are trapped deep in rigid bone. As biologist Dr. Sheldon Weinbaum put it, they “live in caves.” How do they know what’s going on? How can bone adapt to anything? There are several mechanisms. It’s worth going over a couple of them.
The corollary of Wolff’s law for soft tissue is the obscure and much less developed Davis’ law.1 Although there’s no question soft tissue does adapt to stress, the responses of muscles, tendons, and ligaments are much more complex, varied, and less well understood. Bone is one tissue. “Soft tissue” is a whole spectrum of tissues with diverse functions and properties.
The adaptations of soft tissues are as varied as the inhabitants of a zoo. Bone is one tissue. “Soft tissue” is a whole spectrum of tissues with diverse functions and properties. The adaptations of soft tissues are as varied as the inhabitants of a zoo. In its mildest form, Davis’ law is simply the “use it or lose it” principle: the growth of muscles in response to exercise, say. At the other extreme of stress — trauma — scarring is a fairly obvious soft tissue “adaptation.” An intermediate example would be the way we can “seize up” — everything from minor transient sticky adhesions between layers of tissue, to significant shortening of structures. Heavily used tendons go through a complex progression of responses to stress that leads to repetitive strain injury if pushed too far.
Flexibility is a wonderfully complex example. On the one hand, it’s obvious that the soft tissues of extremely flexible athletes like dancers, gymnasts and martial artists have been changed by years of stretching regimens — often brutal and injurious. For most of the rest of us, however, there’s good evidence that flexibility changes are all in the mind: a neurological adaptation, and not a change in the tissue.2 Does a difference in the behaviour of physical unchanged soft tissue count as an example of Davis’ law? Your guess is as good as mine — it’s an almost philosophical question.
The Twa people of Africa provide another great example. A lifetime growing up climbing trees leads to amazing ankle mobility:3
These guys have a huge range of motion into dorsiflexion. They can get their foot almost forty five degrees to the shin. (The normal range of motion for a westerner is about ten to twenty degrees.) This allows them to get their body weight closer to the tree which makes climbing much easier.
Barefoot Running, Squatting Like a Baby, and Pygmy Feet, Hargrove (www.bettermovement.org)
You gotta be
Cruel to be kind in the right measure
Cruel to be kind it's a very good sign
Cruel to be kind means that I love you
Baby, you gotta be cruel to be kind
Nick Lowe, Cruel To Be Kind
Use It or Lose It has a mean cousin: No Pain, No Gain. Many treatments for painful problems are based on the idea of forcing adaptation or “toughening up” tissues by stressing the tissues — a fairly aggressive exploitation of Davis’ law. These are provocation therapies. They claim to cure by doing a little bit of careful damage first — breaking eggs to make an omelette. It’s an emotionally compelling treatment idea. Maybe it’s right, or half right. Or maybe it just makes it a terrific engine for placebo.4
Prolotherapy was invented by a charismatic doctor decades ago to treat back pain by toughening up ligaments by injecting them with an irritant. These days we know that “weak ligaments” are not why people get back pain,5 and so it’s not too surprising that the direct evidence is inconsistent and unimpressive at best. Prolotherapy’s earnest founder got genuinely fantastic results in his own clinic … but those results couldn’t be reproduced anywhere else, by anyone else, ever again, and did not even begin to stand the test of time. However, it continues to be tried and tested for many conditions, and there are promising shreds of evidence here and there. (I have a more detailed review of Prolotherapy for back pain in my low back pain tutorial.)
A more modern example of provocation therapy is eccentric loading (contracting while lengthening) of tendinitis. The jury is out on that one — some of the evidence is promising, some of the evidence is discouraging.
From alternative medicine, the eponymous Graston Technique (GrastonTechnique.com), mostly practiced by chiropractors, is a form of strong massage using hard, edged tools — an extreme form of ordinary friction massage. There are also other “brands” of hard tool massage, rather grandly referred to collectively as Instrument Assisted Soft Tissue Mobilization (IASTM). All use sharp-looking steel or ceramic tools to apply scraping pressure and achieve “maximum tissue penetration.” Although not always painful, it often is — as a provocation therapy must be in principle. In particular, its goal is to “break down scar tissue and fascial restrictions,” and may target tissues that are chronically painful, like a case of tendonitis. It is generally badly over-hyped. There is virtually no positive evidence from clinical trials of this kind of massage,67 and at least two examples of tools having some minor benefit, but — crucially — no more than non-tool techniques.89 Even IASTM proponents had confessed it. Leonard Van Gelder, a self-described “huge advocate of IASTM,” but apparently also a critical thinker, writes:
There are some who have purported [IASTM] tools as being downright magical in their abilities to “heal” patients. Some major brands claim 80-100% success rates for nearly every musculoskeletal condition under the sun, but record and maintain these records privately, available on request only. From the published experimental study realm, far less data is available.
What IASTM is, is not, and might be, Gelder (dynamicprinciples.wordpress.com)
And of course claims of high success rates are almost nonsense by definition.10
It’s not hard to imagine! Clearly there is a risk of hurting instead of helping. The physiology of adaptation may be impressive, but it’s just as clear that too much stress is injurious. And one person’s “just right” may well be the next person’s “too much.”
We also now know, thanks to the last 20 years of chronic pain science, that chronic pain is often a failure of nervous stem itself. Many people with serious chronic pain problems — the very same desperate patients who might try something riskier — are actually pathologically oversensitive. Pain can make us more sensitive to more pain.11 What happens if you “stress” a nervous system in that condition? Simple: the problem gets worse, not better.
And, finally, brand new research has shown quite conclusively (and graphically, on video!) that inflammation can be actively destructive to tissues: like a gang of insane firefighters, immune cells deliberately over-react and destroy healthy cells just in case there might be an infection.12 This response is completely appropriate in open wounds, but dramatic overkill for all minor internal injuries — like tendonitis. Indeed, it may be a major reason for the stubbornness of conditions like tendonitis. Any provocative, intense treatment unquestionably has the potential to provoke exactly this reaction.
Potentially dangerous treatments should never be sold to patients on the basis of scant data. We shouldn’t take risks without proven potential for benefit. There is no reason to think that it will necessarily go well to provoke tissue, and I just spelled out at least two theoretical reasons it could go badly. One person’s “just right” may well be the next person’s “too much.”One of the only studies of scraping massage was a study in rats showed modest benefits.13 But what if, upon studying more rats, you found that some had a nasty reaction? What if all rats tolerate tendon scraping well … but one in a hundred humans is seriously injured?14 Different kinds of tendonitis won’t necessarily respond the same way to the same treatment, let alone completely different musculoskeletal conditions.
The safety of an aggressive treatment is something that should be tested thoroughly, to find out if the potential rewards outweigh the risks. Patients should be wary of overconfidence about these treatments.
Provocation therapy has always been a reasonable notion to test, but the devil is in the details: what constitutes the “right” amount and kind of stress is extremely hard to determine — it probably depends on some genetics, for instance — and consequently the results of such therapies have generally always been super duper inconsistent. Probably some conditions and people benefit from toughening up and others don’t. Your mileage will vary! And naturally provocation therapies are inherently risky.
I am a science writer, former massage therapist, and assistant editor of Science-Based Medicine. I have had my share of injuries and pain challenges as a runner and ultimate player. My wife and I live in downtown Vancouver, Canada. See my full bio and qualifications, or my blog, Writerly. You might run into me on Facebook and Google, but mostly Twitter.
The Twa people of Africa and you will earn amazingly limber calves that allow your ankles to bend half way (45˚) to the shin — two to four times greater than the average urban person! See: Twa man climbs a tree 0:48.BACK TO TEXT
Dr. Harriet Hall reviews the minimal science of Graston Technique for ScienceBasedMedicine.org, with her usual dry wit.BACK TO TEXT
It’s doubtful that this tiny trial was actually of high quality. However, it is notable for being one of the only clinical trials of provocation therapy with instrument massage, and the results were positive. Noted, with a huge grain of salt.In science, positive evidence from a single source, even a high quality source, doesn’t count for much. This is just too little data to take to the bank. BACK TO TEXT
A small clinical trial comparing treatment of carpal tunnel syndrome with standard “soft-tissue mobilization” to “instrument-assisted soft-tissue mobilization” (specifically Graston Technique tools). Both appeared to have modest benefits, but using tools was no better: “the clinical improvements were not different between the 2 manual therapy techniques.”BACK TO TEXT
A small clinical trial comparing treatment of tennis elbow with augmented soft tissue mobilization (tool massage) to “advice on the natural evolution of lateral epicondylitis, computer ergonomics, and stretching exercise.” Both helped a bit, and tools were no better.BACK TO TEXT
Pain itself often modifies the way the central nervous system works, so that a patient actually becomes more sensitive and gets more pain with less provocation. That sensitization is called “central sensitization” because it involves changes in the central nervous system (CNS) in particular — the brain and the spinal cord. Victims are not only more sensitive to things that should hurt, but also to ordinary touch and pressure as well. Their pain also “echoes,” fading more slowly than in other people
For a more information about this paper, see Pain Changes How Pain Works.BACK TO TEXT
Researchers at the University of Calgary Faculty of Medicine are using an innovative new imaging technique to study how white blood cells (called neutrophils) respond to inflammation, and have revealed new targets to inhibit the response. Basically this research explains why neutrophils unnecessarily “swarm” sterile injury sites, causing damage and pain with no direct benefit — a biological glitch with profound implications.BACK TO TEXT
This small study of rats attempted to demonstrate the possible relevance of Graston Technique to tendon healing. It is cited as the sole example of scientific research supporting the clinical use of Graston Technique. Although it does provide some interesting and positive findings, it is a small study of rats — serious limitations. Rat tendons were injured with a collegenase injection, allowed to heal for three weeks, and then some were treated with Graston Technique. Their gait improved more than untreated rats. The authors claim that the results “suggest” that “may promote healing via increased fibroblast recruitment.” Such cautious phrasing is appropriate: although promising, the effect of treatment on five rats is hardly conclusive.BACK TO TEXT