Sensible advice for aches, pains & injuries

Tissue Provocation Therapies

Can healing be forced? The laws of tissue adaptation & therapies like Prolotherapy & Graston Technique

updated (first published 2012)
by Paul Ingraham, Vancouver, Canadabio
I am a science writer and a former Registered Massage Therapist with a decade of experience treating tough pain cases. I was the Assistant Editor of for several years. I’ve written hundreds of articles and several books, and I’m known for readable but heavily referenced analysis, with a touch of sass. I am a runner and ultimate player. • more about memore about

Adapting? Or failing?

How tissue copes with stress is still remarkably mysterious.


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.

full article 3000 words

“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.

Going soft: Davis’ law

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, ligaments, and intervertebral discs are much more complex and less well understood. Bone is one tissue, but “soft tissue” is a whole spectrum of tissues, with diverse functions and properties, as varied as the inhabitants of a zoo. “Soft tissue” is a whole spectrum of tissues, with diverse functions & properties, 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 (

Finally, the best example of all: we now know, thanks to first evidence of its kind published in 2017, that intervertebral discs do adapt to exercise.4 These structures have always been considered one of the least adaptable soft tissues. For decades, almost everyone has assumed that the jarring impact of running constitutes a source of relentless wear and tear on the spine, and that the discs in particular probably cannot keep up with the onslaught, and aren’t able to adapt and recover — a slow losing battle. Specifically, data on “turnover rates” — how quickly tissue is replaced — have “lead to the assumption that positive adaptation in the mature intervertebral disc is unlikely to occur during the normal human lifespan.”

But that’s all wrong: the lumbar intervertebral discs actually adapt well to the forces involved in running. They get fatter and juicier! Tellingly, not just any old running will do, and it’s not a straightforward more-is-better relationship. It’s quirky. There is a sweet spot, but it’s in the pacing, not the volume: regardless of distance, the discs adapt best to a moderate speed, a just-right amount of impact found in slow running and fast walking. Only careful research will elucidate exactly what it takes to coax adaptation out of tissues.

Tough love: the thinking behind provocation therapies

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.5

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,6 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) for tendinitis.7 Eccentric contractions are (curiously) a more challenging stimulus than regular contractions — they consistently make people much more sore after exercise (delayed-onset muscle soreness). To the extent that eccentric loading makes us sore, it’s a provocative stimulus, causing minor damage and then adaptation in the muscle (which is a normal part of strength training). Whether eccentric loading forces useful adaptation in unhealthy tendons is another matter. The jury is out on that one — some of the evidence is promising, some of the evidence is discouraging.

Care for a little tendon massage?

The steel massage tools of
Graston Technique®.

From alternative medicine, the eponymous Graston Technique (, 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, like Astym® or the Chinese gua sha; they are known 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 tendinitis. It is generally badly over-hyped. There is no compelling positive evidence from clinical trials of this kind of massage,8910 some very damning results,11 and at least two examples of tools having showing some minor benefit, but — crucially — no more than non-tool techniques.1213 There are seven notable studies in as of 2017, and they were reviewed by Cheatham et al with a predictable result (see note for more detailed analysis):14

The current research has indicated insignificant results which challenges the efficacy of IASTM as a treatment for common musculoskeletal pathology.

Even IASTM proponents have confessed the problem. 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 (

And of course claims of high success rates are almost nonsense by definition.15

What could possibly go wrong?

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 pain science, that chronic pain is often a failure of nervous system itself. Many people with serious chronic pain problems — the same desperate patients who might try something riskier — are actually pathologically oversensitive. Pain can make us more sensitive to more pain.16 What happens if you “stress” a nervous system in that condition? Simple: the problem gets worse, not better.

Gua Sha rash

The results of a Gua Sha treatment, a more aggressive ancestor of modern tool-massage. It roughly translates to “scrape or scratch, causing a rash.” Although Gua Sha is intense and not widely practiced, I have heard from many people over the years who have been treated like this.

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.17 This response is exactly what we want for open wounds, but overkill for all minor internal injuries — like tendinitis. Indeed, it may be a major reason for the stubbornness of conditions like tendinitis. 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.18 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?19 Different kinds of tendinitis 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.

About Paul Ingraham

Headshot of Paul Ingraham, short hair, neat beard, suit jacket.

I am a science writer, former massage therapist, and I was the assistant editor at for several years. 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 or Twitter.

What’s new in this article?

JuneAn especially neat science update about changes in intervertebral discs in runners (Belavý).

JanuaryScience update. Cited a new review of all relevant research so far (Cheatham et al). Also clarified the example of eccentric loading.

2016Science update. Cited a high quality new study of Graston technique, Crothers et al.



  1. No one seems to know who Davis was. Whoever he was, I was only dimly aware of his law before preparing this post. The Wikipedia entry for Davis’ law is anemic. BACK TO TEXT
  2. If not entirely, at least substantially. It seems like some physical adaptation must be occurring in the examples of gymnast, contortionists and martial artists. But for most people, most of the time, simple stretch tolerance is a strong candidate theory to explain modest increases in flexibility with stretching. I cover this in considerable detail in the second half of my main stretching article, Quite a Stretch. BACK TO TEXT
  3. Venkataraman VV, Kraft TS, Dominy NJ. Tree climbing and human evolution. Proceedings of the National Academy of Sciences of the United States of America. 2012 Dec. PubMed #23277565. PainSci #54672.

    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.

  4. Belavý DL, Quittner MJ, Ridgers N, et al. Running exercise strengthens the intervertebral disc. Scientific Reports. 2017 Apr;7:45975. PubMed #28422125. PainSci #53606. BACK TO TEXT
  5. As a general rule, placebos are always more powerful when people think a medicine is more “potent,” and we all assume that potency correlates with harshness. Things that taste bad, hurt, or feel awful at first must be powerful medicine … right? BACK TO TEXT
  6. For instance, low back pain does not correlate at all with the “looseness” of ligaments, and therefore logically it cannot in general benefit from “tightening” them. BACK TO TEXT
  7. About “tendinitis” versus “tendonitis”: Both spellings are considered acceptable these days, but the first is technically correct and more formal, while the second is an old misspelling that has only achieved respectability through popular use. The word is based on the the Latin “tendo” which has a genitive singular form of tendinis, and a combining form that is therefore tendin. (Source: Stedmans Electronic Medical Dictionary.) BACK TO TEXT
  8. [Internet]. Hall H. The Graston Technique: Inducing Microtrauma with Instruments; 2009 Dec 29 [cited 12 Oct 11].

    Dr. Harriet Hall reviews the minimal science of Graston Technique for, with her usual dry wit.

  9. Wilson JK, Sevier TL, Helfst R, Honing EW, Thomann A. Comparison of Rehabilitation Methods in the Treatment of Patellar Tendinitis. Journal of Sports Rehabilitation. 2000;9(4):304–314. PainSci #54747.

    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
  10. McCormack JR, Underwood FB, Slaven EJ, Cappaert TA. Eccentric Exercise Versus Eccentric Exercise and Soft Tissue Treatment (Astym) in the Management of Insertional Achilles Tendinopathy. Sports Health. 2016;8(3):230–237. PubMed #26893309. PainSci #53623.

    A tiny, flawed test of scraping massage (Astym) for Achilles tendinopathy, comparing it to exercise (eccentric contractions). With just eight subjects given Astym, this is a seriously underpowered study, and Astym did not reduce pain significantly. The good news is that Astym results were better as measured by a questionnaire and the (notoriously unreliable) “global rating of change” scale. However, Astym subjects spent much more time with therapists, so there’s a strong chance they benefitted from those interactions — a well known effect — and not the Astym. The modestly positive results here simply cannot be trusted without backup.

  11. Crothers AL, French SD, Hebert JJ, Walker BF. Spinal manipulative therapy, Graston technique® and placebo for non-specific thoracic spine pain: a randomised controlled trial. Chiropr Man Therap. 2016;24:16. PubMed #27186365. PainSci #53346. This study bills itself as the first “fully powered” trial comparing Graston technique® to a placebo (a fair claim to the best of my knowledge). The experiment was fairly careful, large (143 patients), and long term (a year). Disability and pain were the primary outcomes. The results were resoundingly negative: everyone got slowly better, whether they received Graston or a placebo. BACK TO TEXT
  12. Burke J, Buchberger DJ, Carey-Loghmani MT, et al. A pilot study comparing two manual therapy interventions for carpal tunnel syndrome. J Manipulative Physiol Ther. 2007 Jan;30(1):50–61. PubMed #17224356.

    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.”

  13. Blanchette MA, Normand MC. Augmented soft tissue mobilization vs natural history in the treatment of lateral epicondylitis: a pilot study. J Manipulative Physiol Ther. 2011 Feb;34(2):123–30. PubMed #21334545.

    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.

  14. Cheatham SW, Lee M, Cain M, Baker R. The efficacy of instrument assisted soft tissue mobilization: a systematic review. J Can Chiropr Assoc. 2016 Sep;60(3):200–211. PubMed #27713575. PainSci #53642.

    This is the first review of studies of an unusual and controversial massage technique: using tools to “scrape” soft tissue. The authors evaluated seven studies, five of which were controlled, and “the results of the studies were insignificant with both groups displaying equal outcomes.” Although there’s not much good evidence to review, the research so far “challenges the efficacy of IASTM as a treatment for common musculoskeletal pathology.”

    One slightly positive note was that there is “some evidence supporting its ability to increase short term joint ROM,” for whatever it’s worth (not much — short term increases in ROM have no clear clinical value in and of themselves). As always, more study is needed, and some benefits might be discovered by studying the right people in the right way, but the first several tests have failed to show any obvious benefit.

  15. I’m often asked what I think of a treatment that supposedly has a “100% success rate.” Or any percentage over 90, really. It’s the same answer, every time: hyperbolic treatment claims in health care are bollocks (and are almost always part of a sales pitch). Most painful problems are not really one problem. Perfect treatment results are nonsense due to co-morbidities & multiple overlapping etiologies alone. Nothing can treat everything. In fact, nothing can treat anything reliably. BACK TO TEXT
  16. Woolf CJ. Central sensitization: Implications for the diagnosis and treatment of pain. Pain. 2010 Oct;152(2 Suppl):S2–15. PubMed #20961685. PainSci #54851.

    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 much more detailed summary of this paper, see Central Sensitization in Chronic Pain.

  17. McDonald B, Pittman K, Menezes GB, et al. Intravascular danger signals guide neutrophils to sites of sterile inflammation. Science. 2010 Oct;330mcd(6002):362–6. PubMed #20947763.

    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. Collateral damage!

  18. Davidson CJ, Ganion LR, Gehlsen GM, et al. Rat tendon morphologic and functional changes resulting from soft tissue mobilization. Med Sci Sports Exerc. 1997 Mar;29(3):313–9. PubMed #9139169. PainSci #55795.

    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, so it has 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.

  19. A 1% rate adverse effect rate is high — but you could do five human studies, using treatment groups of 20 each, encounter only a single example, and you still wouldn’t have a clue about the real statistical risk. Graston Technique poses a real potential danger, yet its safety hasn’t been studied at all. This is precisely the kind of thing that makes peoples heads explode about drugs — foisting serious side effects on the public, no matter how rare, is the stuff of scandal! BACK TO TEXT