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Quite a Stretch

Stretching science shows that a stretching habit isn’t doing much of what people hope

updated
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 ScienceBasedMedicine.org 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 PainScience.com

An audio version of this article is freely available to visually impaired visitors. Please email requests for audio to paul@PainScience.com and I will send a download link within a day, but usually much faster. There are audio versions of seven other popular articles on the site.An audio version of this article is freely available to visually impaired visitors. Please email requests for audio to paul@PainScience.com and I will send a download link within a day, but usually much faster. There are audio versions of seven other popular articles on the site. audio version available infoThis is one of seven articles available in audio format as a free bonus for e-boxed set customers. For more information, see PainScience.com Audio Articles.

SUMMARY

Stretching just doesn’t have the effects that most people hope it does. Plentiful research has shown that it doesn’t warm you up, prevent soreness or injury, enhance peformance, or physically change muscles. Although it can boost flexibility, the value of this is unclear, and no other measurable and significant benefit to stretching has ever been proven. Regardless of efficacy, stretching is inefficient, “proper” technique is controversial at best, and many key muscles are actually biomechanically impossible to stretch — like most of the quadriceps group (which runners never believe without diagrams). If there’s any hope for stretching, it might be a therapeutic effect on muscle “knots” (myofascial trigger points), but even that theory is full of problems.

full article 13000 words

Stretching is a pleasant ritual for many people, myself included. It’s simple, it feels good, and we believe — or hope — that it prevents and treats injuries. For many others, athletes and couch potatoes alike, stretching is also a bit of a drag: a duty that weighs on the conscience, one more thing to make time for. And yet they still do it, counting on the benefits.

Can all these people be barking up the wrong tree? Yes. This (large) article makes the scientific case against the typical stretching habit in detail.

I stretch almost every day — hamstrings, lumbar erector spinae, and especially the deep gluteals are my favourites — but I don’t believe the habit is doing much more for me than a daily back scratch. I am just as stiff and inflexible and full of “knots” as I have ever been. I play sports the same way with or without it. I still get just as sore, whether I stretch or not. The science supports my skepticism, and I am hardly the only person to notice that stretching may not be all it’s cracked up to be…


Why is it that many Kenyans don’t stretch? Why was legendary coach Arthur Lydiard not a fan of stretching? Why does Galloway say, “In my experience runners who stretch are injured more often, and when they stop stretching, the injuries often go away”?

— Bob Cooper, Runner’s World Magazine1

What a sensible article, and about time somebody exploded the stretching myth! I remember as a schoolboy in South Africa forty years ago always being told to run slowly to warm up for our various rugby, cricket, and soccer games — nobody ever told us to stretch, and over the past ten or so years I’ve been puzzled to see this come in as dogma. As a runner of marathons for years and a GP with injured patients, I’ve never been able to figure out how on earth stretching the heck out of muscles, ligaments, and nerves could (a) warm them up or (b) do the slightest bit of good, and have sometimes been given “the jaundiced eye” when I’ve suggested such to my patients.

— Peter Houghton, MD, Vancouver (reader feedback)

I am a soccer referee, and mostly by happy accident began substituting what you call “mobilizing” for various stretches prior to my matches, and I find this does an excellent job of stimulating the muscles, whereas after only stretching I still seem to be tight for the first several minutes. Then I read this article, which corroborates what I have found in practice!

— Carlos Di Stefano, soccer referee (reader feedback)

TABLE OF CONTENTS
  1. 1 Introduction
  2. 1.1 There is no “truth” about stretching
  3. 1.2 Why people stretch: the five most popular reasons
  4. 1.3 Types of stretching (not just static)
  5. 2 Stretching: the evidence
  6. 2.1 Stretching research clearly shows that stretching is not an effective warmup
  7. 2.2 Stretching research shows that stretching does not prevent exercise soreness
  8. 2.3 Stretching research shows that stretching does not prevent injury
  9. 2.4 Stretching can cause injuries
  10. 2.5 Yes, stretching research shows that it will make you more flexible … but so what?
  11. 2.6 Stretching research shows that stretching probably doesn’t enhance performance (and it definitely doesn’t make you sprint faster)
  12. 3 So … is stretching good for anything?
    Responses to several common objections and ideas about stretching (and some of my own)
  13. 3.1 So if all that’s true, then why is it that I feel like I have to stretch or I’m going to seize up like an old piece of leather? Why do I have this compulsion to stretch, and why does it feel so good, if it’s not actually doing anything?
  14. 3.2 “But I find that stretching helps my aches and pains…”
  15. 3.3 “But don’t people just need to be taught how to stretch properly?”
  16. 3.4 “But isn’t yoga all about stretching? And Yoga has lots of benefits, doesn’t it?”
  17. 3.5 The unstretchables: the many muscles that are biomechanically impossible to stretch
  18. 3.6 Is stretching good for tendons? Can it align their fibres?
  19. 3.7 Scratching your inner itch: a feel-good theory
  20. 4 Back to the question of flexibility
  21. 4.1 The last theory standing: tolerance
  22. 4.2 Let’s get neurological
  23. 4.3 The wisdom of the body
  24. 4.4 Stretching for contracture: Thumbs down to static stretching as a treatment for seizing up
  25. 5 So stretching is good for … stretching?
  26. 6 Appendices
  27. 6.1 More reading
  28. 6.2 What’s new in this article?
  29. 6.3 Notes
dots before headings indicate updated sections ?There’s a detailed description of all updates at the bottom of the article, and it’s nice to be able to see what’s new at a glance in the table of contents. Any section updated in the last 400 days is marked (hotter colours = fresher updates).
About footnotes. There are 53 footnotes in this document. Click to make them pop up without losing your place. There are two types: more interesting extra content,1Footnotes with more interesting and/or fun extra content are bold and blue, while dry footnotes (citations and such) are lightweight and gray. Type ESC to close footnotes, or re-click the number.
and boring reference stuff.2“Boring” footnotes usually contain scientific citations from my giant bibliography of pain science. Many of them actually have pretty interesting notes.

Example citation:
Berman BM, Langevin HH, Witt CM, Dubner R. Acupuncture for Chronic Low Back Pain. N Engl J Med. 2010 Jul 29;(363):454–461. PubMed #20818865. PainSci #54942. ← That symbol means a link will open in a new window.
Try one!

There is no “truth” about stretching

There are too many mysteries in muscle and connective tissue physiology, too many different stretching methods, and too many and vague and overlapping goals for it to ever be possible to claim that stretching does or does not “work.” What kind of stretching? With what purpose? There are too many possibilities for any tidy summary.

However, plentiful recent research now shows that stretching as we know it — the kind of typical stretching that the average person does at the gym, or even the kind of stretching that most athletes do — is mostly a waste of time for most commonly identified goals. For instance, scientific reviews have concluded that there isn’t much evidence that any widely practiced form of stretching prevents injury or muscle soreness.23 A major year 2000 clinical study of many hundreds of soldiers showed no benefit and even some risks to stretching.4 Some extremely popular stretches, like IT band stretching for runners with knee pain, have dubious value.

Trainers, coaches, and health care professionals are starting to insist on making recommendations based on evidence, or at least on a really convincing physiological rationale … and stretching just has not held up well under that pressure. Nor is it even a new idea that stretching might not be all that helpful. Consider this 35-year-old passage from an excellent 1983 Sports Illustrated article about David Moorcroft, a British middle and long distance runner and 5,000 metres world record holder:5

Stacked in a corner of Anderson’s [Moorcroft’s coach] office are bundles of scientific papers. “I’ve tried to interpret the findings of the best physiologists and translate them into sound practices,” says Anderson. “That’s made me a radical. We’ve turned some coaching sacred cows on their ear.”

For one, Anderson dismisses the stretching that most runners do. “It’s rubbish,” he says. “The received idea that by touching your toes you lengthen the fibers in your hamstrings is wrong. Soft tissue stretching like that is a learned skill and doesn’t carry over into running. Dave requires flexibility, and joint mobility, but running fast is the right kind of stretching for him.”

The world-record holder mutely demonstrates his suppleness by reaching toward his toes. His fingertips get down to about midshin.

~ 'What Made Him Go So Wonderfully Mad?' So Inquired a friend of David Moorcroft after the Briton broke the world 5,000 record in an amazing performance, Moore (Sportsillustrated.cnn.com)

So why are people stretching?

Why people stretch: the five most popular reasons

When challenged, many casual stretching enthusiasts — and even many not-so casual ones — actually have a hard time explaining why they are stretching. Everyone just “knows” that it’s a good thing, and they haven’t really thought about why. It’s dogma, practically a religion. “Beliefs about flexibility and the optimal means of stretching have often proceeded from assumptions that have never been tested and from an almost religious zeal regarding the perceived benefits of stretching by a few.” (Sands) When pressed for reasons, most people will cough up a few predictable stretching goals. Here are the four hopeful reasons for stretching that I hear every day:6

  1. flexibility, of course7
  2. warm up and injury prevention
  3. treatment of muscle soreness and stiffness

And occasionally I hear this one as well:

  1. “performance enhancement” (e.g. faster sprinting)

All of these overlapping stretching goals have serious problems. Either they have have long ago been proven to be impossible,8 or they never made sense to begin with, or both, or worse. Certainly none of them is a slam dunk.

The treatment of muscle soreness and stiffness with stretch is particularly popular and complicated, but will also mostly be left out of this article, because it’s a huge topic and quite different from the others.9 I get into some of the basics below, much more detail in a separate article, Stretching for Trigger Points, and I go on about it for thousands of words in my book about trigger points.

One final reason for stretching gets mentioned surprisingly infrequently (people seem to prefer to give more “technical” reasons for their stretching):

  1. it feels great!

This may be the best reason for stretching. 😃 Just ask Murmel:

I stretch because it feels good. Just a couple seconds stretching this-a-way, then a couple more that-a-way, and I’m good to hop. Don’t overdo it! Holding stretches is over-rated.

~ Murmel the bunny, master stretcher

Types of stretching (not just static)

This article is emphatically not just about the inadequacies of simple “static” stretching.

Many stretching advocates are happy to join me in criticizing simple, old-school stretching — that is, elongating a muscle and then holding still for a while — because they have decided that some other method of “stretching” actually does work. Unfortunately, I have yet to see clear evidence that any stretching method is a clear winner for any important therapeutic goal.

For instance, alternately stretching and contracting a muscle is a staple of “advanced” stretching. This is called the contract-relax (CR) method, which is part of a general strategy with the very advanced sounding name of “proprioceptive neuromuscular facilitation” (PNF). However, it’s really nothing fancy: CR just adds contraction. Some readers will sniff at this and say that CR is still not “advanced” stretching, but it is certainly still widely used, taught, and touted as being better than humble static stretching. I see trainers using it at the gym all the time. Patients can go for physical therapy pretty much anywhere in the world, and there’s a good chance the therapist will do a whole bunch of CR stretching with them, while charging about a buck a minute.

It doesn’t increase flexibility any more than static stretching.10 In 2011, researchers compared a normal CR stretch of the hamstring to a modified one without any hamstring contraction (instead, some other “uninvolved, distant” muscle was contracted). The effect of both stretches was the same — a “moderate increase in range of motion,” which is the one thing that stretching will achieve. It didn’t matter if the hamstring was contracted or not — with or without a contraction, the result was the same: a slight increase. This destroys the central claim of CR-PNF stretching.

Things that sound too good to be true … still aren’t.

Some supposedly advanced methods of stretching are not really “stretching” at all. There are only so many things that you can change about stretching before it really becomes something else. The classic example is dynamic joint mobility drills — repeatedly moving through a range of motion (i.e. swinging your arms in a circle). Should we call that “stretching”? Perhaps. But I say no: although the kinship is clear, it already has its own name. It’s a movement exercise, not “stretching.”

If an exercise doesn’t involve elongating muscles for at least several seconds, it’s not stretching. It might be interesting or worthwhile, but it’s not stretching.

Part 2

Stretching: the evidence

Stretching research clearly shows that stretching is not an effective warmup

You cannot “warm up” your muscles by stretching them: it’s like trying to cook a steak by pulling on it. Instead, the best way to warm up is probably to start by doing a kinder, gentler version of the activity you have in mind (i.e. walk before you run). The metabolic activity involved in muscle contraction does literally warm up your muscles, which is an inevitable side effect of evertyhing does that make a warm up effective at preventing injury.

Nothing about static stretching is more clear. Your basic quick (static) stretch warmup is one of the most studied topics in all of musculoskeletal health care and exercise science. For instance, a huge 2011 review of all the research found “overwhelming evidence that stretch durations of 30-45 seconds … imparted no significant effect” and even some evidence of harm.11

Um, harm? Slight harm, yes: a 2014 test found that a nice pre-run stretch causes “a reduced capacity of the skeletal muscle to produce explosive force.” Yikes. As Alex Hutchinson put it for Runner’s World, “I can’t see anything good about something that makes me go slower but feel like I’m trying harder.”12 And there’s more like that.13

Metaphorically, “warming up” also refers to readiness for activity or body awareness. You are “warm” in this sense when you are neurologically responsive and coordinated: when your reflexes are sensitive and some adrenalin is pumping. Warmup for its own sake (i.e., without following it up with more intense exercise) is fairly pointless — the goal is to prevent injury and enhance performance. And those goals may be realistic. For instance, research has shown that a warmup routine focused on these goals actually does provide decent insurance against the number and severity of both accidents and over-use injuries.1415

So, warmups in this second sense is probably helpful … but does stretching warm you up in this sense? No, probably not much — certainly no more than a bunch of other exercises you could do — and quite possibly not at all. One of the most-studied warmup regimens (including one of the studies just cited), FIFA’s “The 11+” programme, notably does not include stretching. The most compelling evidence that stretching doesn’t warm you up is the evidence that shows that it doesn’t prevent injury or enhance performance (discussed below). Static stretch is somewhat stimulating to tissue, but in ways that are quite different from most actual activities.

Warmup works

A large study of girls’ soccer teams showed warming up can cut injury rates by about a third. Notably, the warmup that was studied, FIFA’s “11+” warmup, did not include stretching!

Because of all this, stretching to warm up does not even qualify as “official” exercise dogma anymore — most professionals actually gave up on it many years ago, and it is passé even in the opinion of a great many more informed joggers and weekend warriors. It simply doesn’t work, and it’s hard to imagine a common fitness practice more thoroughly contradicted by the evidence and by many professionals. And yet …

And yet I still see it all the time in the wild. I live and play on Vancouver’s famous “sea wall” — one of the best and most popular running routes in the world. I am able to constantly observe runners in their natural habitat, doing what runners do, and a great many of them participating in structured training programs and running groups, clearly being instructed by experts and coaches.

And they stretch to warm up. In droves. So despite the evolution of professional opinion, this practice clearly still needs to be debunked. There are still far too many people out there stretching before they run and play sports, trying to “warm up” almost exclusively by standing still and elongating muscles!

Once again, the best way to prepare for an activity is probably just to start it slowly.

Stretching research shows that stretching does not prevent exercise soreness

Another popular idea about stretching is that it prevents the deep soreness that follows a hard workout. That soreness is called “delayed-onset muscle soreness,” or DOMS for short. Many people believe that stretching can help DOMS. Some seem to believe it like it’s their religion, and it’s amazing how determined people can be to ignore evidence that contradicts it.16

Recently (2016), decades after this faith first got entrenched, science finally coughed a specific reason why it might be based on something: evidence that stretching reduces inflammation in connective tissue.17 Surely that’s relevant! It sure sounds like great science factoid to explain why people think stretching helps soreness after exercise. Practically a slam dunk! It is interesting evidence for sure, and I’ll return to it later.

But there are many problems with leaping to that conclusion.18 It’s a classic mistake to assume that a scrap of biological relevance translates into a clear benefit in the real world. Unfortunately, the evidence strongly suggests that stretching does not prevent DOMS. Many studies have shown that nothing short of amputation can prevent DOMS192021 — and certainly not stretching.22 Whatever effect stretching has on inflammation in connective tissue, it does not add up to a DOMS cure.

Stretching research shows that stretching does not prevent injury

The commonly accepted idea that increased ROM and stretching prior to activity prevents injuries has been challenged and found to be on the shakiest of scientific foundations, or to come from such a paucity of data that no reasonable conclusions can be drawn.

~ Flexibility, by William Sands, p. 389

According to the evidence, stretching probably does not prevent injury. As I mentioned above, this has been suggested by a combination of recent literature reviews and large clinical studies, some of which I have already cited. Here’s some more.

In 2005, the Clinical Journal of Sports Medicine published a review of the scientific evidence to date, and found that the (admittedly limited) evidence “showed stretching had no effect in reducing injuries.”23 Neither poor quality nor higher quality studies reported any injury prevention effect. Regardless of whether stretching was of individual muscles or entire groups, there was no reduction in injury rates.

More experimental research has been done since. For instance, a 2008 study published in the American Journal of Sports Medicine showed “no significant differences in incidence of injury” in soldiers doing preventative exercises.24 Half of them participated in an exercise program including 5 exercises for strength, flexibility, and coordination of the lower limbs, and 50 of those soldiers sustained overuse injuries in the lower leg, either knee pain or shin splints. The other 500 soldiers were doing nothing at all to prevent injury in the lower limbs — no specific stretching, strengthening or coordination exercises — and only 48 of them had similar injuries. There were “no significant differences in incidence of injury between the prevention group and the placebo group,” and the authors concluded that the exercises “did not influence the risk of developing overuse knee injuries or medial tibial stress syndrome in subjects undergoing an increase in physical activity.”

However, what is clear is that the exercise regimen certainly included static stretching, and it certainly did not work any prevention miracles for some of the most common athletic injuries from the knees down. If stretching performs that poorly in such an experiment, how good can it possibly be at preventing other injuries? Probably not very.

Here in Vancouver — a running Mecca — researchers at Simon Fraser University have done an unusually large study of pre-run stretching, with more than 2700 participants. They found “no statistically significant difference in injury risk between the pre-run stretching and non-stretching groups.”25 Injury rates for all kinds of injuries were the same, with or without stretching. It’s almost as though stretching made no difference at all. But make up your own mind!

I’m never surprised by such findings, because I’ve never heard a sensible explanation for how stretching can generally prevent injury. Usually, advocates have a vague notion that “longer” muscles are less likely to get strained: even if garden-variety stretching made muscles longer (which is doubtful in itself), and even if we knew exactly what kind of stretching to do (we don’t), and even if we had the time to stretch every significant muscle group, the benefits would still be relevant to only a small fraction of common sports injuries. An ankle sprain, for instance, or a blown knee — two of the most common of all injuries — probably have nothing to do with muscle length.

Not convinced yet? A 2014 review of exercise therapy for injury prevention in the British Journal of Sports Medicine was completely negative about stretching26 — even though the authors were obviously a bit too optimistic about everything else!27 “Consistently favourable estimates were obtained for all injury prevention measures except for stretching.” Ouch.

There may be some injury prevention powers to stretching — muscle strains seem like the most likely candidate28 — but probably quite specific and missed by many basic, general pre-event stretching regimens.29 For injury prevention, I can think of Sports Injury Prevention Tips that are probably more effective/efficient than stretching.

Stretching can cause injuries

Cartoon of a man stretching his neck alarmingly far to one one side. His neck is a spring that is breaking.

Ironically, stretching can actually cause some of the injuries it is thought to prevent. Although, stretching is mostly a safe activity, especially if practiced with a modicum of caution, there are (at least) four potential types of stretching hazards:

  1. Stretching as a warmup may modestly impair athletic performance, as discussed above.
  2. Overt injury (sprains and strains) from over-stretching, fairly common in yoga, dance, martial arts, and so on. People just overdo it.
  3. Overt injury to people who should never stretch because of medical vulnerabilities directly related to flexibility, like the hypermobility spectrum disorders and connective tissue diseases (e.g. Ehlers–Danlos syndrome, Marfan syndrome).
  4. Unexplained body pain may be worsened by attempts to stretch, for a variety of reasons, probably mostly related to aggravating pre-existing conditions.

Hypermobility and Ehlers-Danlos syndrome

Some people are much more flexible than average — pathologically flexible. “Hypermobility spectrum disorders” (HSD) are a group of conditions defined by joint hypermobility — unexplained joint looseness.30 Ehlers–Danlos syndrome (EDS) is a closely related group with known genetic causes31 that includes hypermobility along with fragile tissues that heal poorly, especially skin, with many consequences. All of these conditions together are quite common, and chronic pain is a routine complication.32

Most people don’t need to stretch, but people with HSD/EDS really should not stretch… and they may not know it. HSD/EDS is often undiagnosed and mistreated; it is clinically important and yet often non-obvious. So lots of people are probably suffering without having any idea why or that they shouldn’t be stretching. Consider this story from a 75-year-old reader:

Upon continued strong urging by my physical therapist, I engaged in “glute” and “quad” stretches — quickly to my detriment and horror. MRI survey confirmed gluteal minimus and medius tendinitis and partial thickness tendon tears. After a year of seeking help and ineffective treatment I was just this month diagnosed by a rheumatologist with hypermobility joint syndrome.

This condition does not seem to be on the “radar” of most docs or PT’s. As a kid, I delighted in acrobatics, some said I was “double-jointed”; and in high school and college, modern dance (which included acrobatics). I was still dancing and hiking up until a year ago, but this injury has been devastating!

Now I understand the problem, so my rehab routine is strengthening within a normal range of motion. Feel-good, easy whole-body stretching only. Swimming has been a great help, along with careful exercising with weights at the gym.

It’s awful that this patient, with a long history of hypermobility, was convinced to overstretch by “strong urging” from a healthcare professional. This is a perfect example of clinical ignorance of hypermobility and the consequences of unjustified enthusiasm for stretching. Most people, even healthcare professionals, are simply oblivious to how common and serious hypermobility is — but it’s highly relevant to the value and safety of stretching.

Other vulnerabilities

Hypermobility is a common vulnerability that is directly related to stretching. There are many other medical conditions that have nothing obvious to do with stretching, but can be aggravated by stretching. A simple example: back pain has many possible causes, several of which might be aggravated by stretching, even severely.

And yet people routinely attempt to self-treat back pain with stretching, more or less oblivious to the possibility that it will do more harm than good in some cases.

In a separate article, I tell the story of my own ill-fated attempt to treat some neck pain with stretching:

Yes, stretching research shows that it will make you more flexible … but so what?

What exactly are you planning to do with your flexibility?

“I want to be more flexible,” people say. Even when they have normal range of motion in every joint. What’s this about? Why are people so determined to be more bendy? What is it you want to do with that super power?

The fact that there are actually several elastic superheroes speaks to our genuine desire for greater range of motion. But the reality is that hardly anyone actually needs to be more flexible. Most people have a normal range of motion — that’s why it’s normal! Unless you are specifically frustrated because you lack sufficient range of motion in a joint to perform a specific task, you probably don’t need to be more flexible.

Stretching can increase flexibility. It’s not necessarily easy, or good bang for buck, and it may depend on your genes. I really can’t seem to do it, which established long ago with a really thorough personal experiment. Many other people feel defeated by this challenge as well. Here’s a story sent in by a reader who has been working on it for decades:

I have done yoga every day more than 20 years. I'm really devoted to it. I do different set of positions every 2 weeks, but I start my sessions every day with 5-10 minutes of breathing in simplified/easier lotus position (padmasana, where one foot is on the floor, and another is on top of the opposite thigh). It is still just as uncomfortable now as it was when I started. I can handle it for those 5-10 minutes, but more is just too hard. I can still do the full version, but only for a minute or so. One would hope after so many years, doing it daily, I would become more flexible! But not even a little bit — I do the yoga for other reasons.

Franjo M, California

However, for many people, a diligent effort over a period of weeks might well increase your range of motion. In 2011, a nicely done experiment by Marshall et al showed that regular hamstring stretching substantially increased range of motion in normal university kids.33 Specifically, after “a 4-week stretching program consisting of 4 hamstring and hip stretches performed 5 times per week,” their range increased about 16˚ or 20%. That’s a real result. For whatever it’s worth.

And more extreme efforts tend to produce more extreme results.

Acrobats, gymnasts, yogis, contortionists, and martial artists have clearly been pushing the limits for centuries, sometimes achieving uncanny mobility. But these are highly motivated athletes with specific and exotic performance goals and stretching regimens that would definitely intimidate the rest of us, and with good reason: they often injure themselves along the way. Indeed, it may even be necessary to injure joints — to traumatize their capsules and ligaments — in order to get them to move that far.

Fitness and health are not equivalent. You can be fit for a particular athletic pursuit, but that doesn’t mean you are a healthier person: high performance in a narrow category often comes at great costs (such as joint stability). Flexibility is good for a few specialized tasks … and really not much else. It’s useful for gymnasts, for instance.

Is this a good idea? This is an “oversplit.” Regularly doing this kind of thing well certainly make aperson flexible … but not “healthy.”

Or this? I’m not sure it’s even a good idea for gymnasts!

Is this child gymnast going to be more flexible? Oh, yes, I think she will be! Is she going to be “healthier” for it? Blatantly not. And she has a middle-aged guy sitting on her back … and that’s just gotta suck.

Flexibility is such a desired goal, however, that I will return to this topic later in the article. There are still some more myths to bust first, though.

Stretching research shows that stretching probably doesn’t enhance performance (and it definitely doesn’t make you sprint faster)

The most flexible athletes are not necessarily the most successful.

~ Flexibility, by William Sands, p. 389

You don’t hear this argument for stretching as often as your hear the others. And yet it comes up, especially with athletes who play team sports. It’s a common practice to stretch when you’re off the field. The habit is probably usually rationalized as an injury prevention method, but many of those athletes will also insist that it enhances their performance — that the muscles “spring back” from the stretch and make them run faster. There’s actually an entire stretching book that is largely based on this idea — but that book is conspicuously full of armchair science, and no actual evidence that the ideas are true.

I’ve already mentioned a huge 2011 scientific review by Kay et al that found “overwhelming evidence” that pre-exercise stretching has “no significant effect.” That was not a surprise. What is a little surprising is that the same review showed the opposite of a benefit — that pre-exercise stretching might reduce muscle strength.34 I wouldn’t take the danger too seriously, but it certainly emphasizes the lack of benefit: if anything, it swings the other way. Yikes!

Similarly, research has shown that stretching does not improve sprinting … but it gets worse. What really happens to your sprint if you stretch first? It turns out that, all other things being equal, the athlete who didn’t stretch is actually going to leave you behind! An Australian research group in Perth did this experiment in early 2009. They rounded up a few athletes and tested their sprinting with and without a stretching regimen between sprints.35 The results of the tests were clear: “There was a consistent tendency for repeated sprint … times to be slower after the static stretching.” In other words, if you want to perform in a sprinty sport, you might not want to stretch right before getting your cleats dirty.

There are many possible mitigating factors here.36 However, the complexities only emphasize the absurdity of the legions of people who have an oversimplified faith that stretching is important. In the face of so much discouraging evidence, it makes sense to assume that sport itself provides all the “stretching” one needs. The late Mel Siff:

It is almost heretical to question this stretching doctrine, yet it is important to disclose that there is no research which proves categorically that there is any need for separate stretching sessions, phases or exercises to be conducted to improve performance and safety. To appreciate this fact, it is useful to return to one of the clinical definitions of flexibility, namely that flexibility refers to the range of movement of a specific joint or group of anatomical tissues. Moreover, flexibility cannot be considered separate from other fitness factors such as strength and stamina. There is no real need to prescribe separate stretching exercises or sessions, since logically structured training should take every joint progressively through its full range of static and dynamic movement. In other words every movement should be performed to enhance flexibility, strength, speed, local muscular endurance and skill, so that separate stretching sessions then become largely redundant.

~ Facts and fallacies of fitness, by Mel Siff, p. 123

Siff’s sensible minimalism — from 1988 — stands in stark contrast to a much more common and marketable “flexibility first” approach, an approach that just happens (coincidence, I’m sure!) to give coaches, trainers and therapists something to be expert about: the idea that athletes must make a point of increasing flexibility first (by whatever stretching method), and then train for the strength and coordination to exploit this marvelous new range of motion. That picture is quite likely to be exactly backwards.

Part 3

So … is stretching good for anything?

Responses to several common objections and ideas about stretching (and some of my own)

How about this? It’s good for your heart!37 “Enhanced vagal modulation.” That’s fairly straightforward good-news science about stretching. (And yet I’ve never heard anyone say they were stretching for heart health.)

It’s not surprising that movement would have some systemic regulatory effects, but it’s nice to see some corroboration of that common sensical notion, and it’s also nice to know that perhaps just stretching did this (to the extent we can learn anything from a single study). If true, it makes for a nice point in favour of a general stretching habit and yoga, “massaging with movement,” and probably even massage itself. It may have a lot to do with why massage feels good.

But stretching is probably not good for the reasons most people are stretching — not much good, anyway, and certainly not much in any ways anyone has figured out how to measure.

Undoubtedly, some specific stretching techniques are good for specific purposes … but quite different from the stretching goals that most people actually have in mind, if they have any clear goals at all. My concern is not that stretching itself is useless, but that people are stretching aimlessly and ineffectively, to the exclusion of evidence-based alternatives, such as a proper warm-up or mobilizations.

I don’t believe that stretching is any more generally useful for people than it is for cats — you do it when you get up in the morning for a few seconds and then you’re off to the sandbox. That feels good — it’s stimulating and enhances your body awareness, it scratches some simple physiological itch, and that’s fine and dandy. But for most people, most of the time? As a time-consuming therapeutic exercise ritual? Stretching simply has a lousy effort-to-reward ratio.

In the next few sections, I will respond to some of the common objections and questions that readers often have.

So if all that’s true, then why is it that I feel like I have to stretch or I’m going to seize up like an old piece of leather? Why do I have this compulsion to stretch, and why does it feel so good, if it’s not actually doing anything?

Because it is probably actually doing something! It’s just probably not doing what you thought it was doing. And we don’t really know for sure what it is doing. If we are intellectually honest, we simply have to admit that.

People routinely report that stretching feels good, that it reduces muscle soreness, or that they feel a strong urge to stretch. And I’m one of them. I have a stretching habit because it feels good, and because it feels like I’m going to “seize up” if I don’t. In particular, I stretch my hamstrings regularly and strongly, and it feels as pleasantly essential to my well-being as slipping into a hot bath — but the exact nature of the benefits are completely unclear to me.

It’s probably a stew of genuine but mysterious and subtle physiological benefits — like the heart rate regulatory effect noted in the last section — plus almost certainly some good placebo, too. I was raised on stretching. Despite my doubt about the conventional wisdom, I tend to emotionally “believe” in stretching just like everyone else — it’s deep in our culture, and, since stretching feels good, it’s easy for my mind to jump to the conclusion that it must be good. But of course that’s not really helpful at all — lots of things feel good without having any clear physiological benefits. Stretching might be like scratching: an undeniably strong impulse, but with almost no relevance to athletic performance or overall health.

I just don’t know. And based on the research to date, no one else does either.

If people believed that feeling good was the only thing that stretching was good for, most people — especially the athletes — would drop it from their exercise routine immediately. Most of us have better things to do. However, if someone firmly declared, “I stretch just to feel good,” I would applaud and say, “Hallelujah! That is an excellent reason to stretch! And one of the few that I can defend!”

And, then again, there may actually be real physiological benefits to stretching — just not the usual ones that get tossed around.

“But I find that stretching helps my aches and pains…”

The anecdotal evidence that stretching “works” for miscellaneous body pain and stiff and aching muscles is substantial. (So is the anecdotal evidence that it can backfire.) There is also some scientific evidence suggesting that stretching is helpful for common stubborn pain problems, such as neck and back pain3839 (but it’s also a complicated, incomplete, underwhelming mess). Stretching doesn’t seem to come close to “curing” anyone, but darned if it doesn’t also seem “take the edge off” enough to make it worth trying. So people in pain stretch, and sometimes they feel a little better for a while.

People who feel stiff and tight assume their range of motion is limited by literally short muscles, but this is rarely the case, despite how it feels. Stiffness isn’t the same as being inflexible. They aren’t even really related. Most stiffness is a sensation, a symptom, a kind of mild pain with movement rather than an actual limitation of movement. Even hypermobile people often feel stiff! Genuinely abnormal muscle tightness (dystonia) is much less common than the symptom of stiffnes (but some milder dystonias do blend right in with other common aches and pains).

There are many possible causes of soreness and stiffness, few of which have anything to do with anything that stretching can help. Good luck stretching your way out of stiffness if it’s caused by drug side effects, for instance.40

If not inflexibility, why do we get stiffer as we age? Why do we feel lik we need to stretch? Probably mainly because of “inflammaging”: chronic low-grade inflammation that gradually escalates over the years for all kinds of reasons, like metabolic syndrome (the biological foundations of heart disease and diabetes). It’s unlikely that stretching can help with that.

For much more ifnormation about the causes of stiffness, see Why Do Muscles Feel Stiff and Tight?

There could be reasons why stretching is good for pain that we don’t understand, or are only just barely starting to understand. For instance, a 2016 study produced evidence that stretching reduces inflammation in connective tissues.42 It’s not clear how much “inflammation in connective tissue” is a factor in common muscle pain — maybe none, maybe lots — but obviously there could be a connection. We do have some evidence that inflamed connective tissue is associated with back pain.43 The evidence is too scanty to trust yet, but it’s suggestive. If stretching does help some inflammation resolve, obviously it could explain why stretching feels good, or even better than that. It wouldn’t even have to be a large or consistent effect (neither are the benefits of pain meds). “Taking the edge off” sometimes would be enough to explain the reputation stretching has for relieving soreness.

Stretching for trigger points

There is one kind of soreness that is common and might be responsive to stretching: the soreness associated with those sensitive, aching spots in muscles commonly known as “muscle knots” or trigger points.

Theoretically, trigger points are isolated regions of contracted muscle fibres — mini cramps. Their nature strongly suggests that stretching might be a treatment method.

Stretching as a treatment for trigger points has some expert endorsements. In the weighty text Muscle Pain, researchers Dr. David Simons and Dr. Siegfried Mense wrote that stretching “by almost any means is beneficial.” This depends on chain of assumptions and theories about how trigger points work: the micro-cramp is metabolically exhausting, like an engine revving in the red, producing waste metabolites that pollute and irritate the surrounding tissues, causing pain and more contraction. In theory, a trigger point cannot burn fuel if it is fully elongated, which would give the energy crisis a chance to abate — a vicious cycle breaker.

If they are right, then stretching works about the same way that stretching out a calf cramp works: you win the tug-of-war with spasming muscle, just on a smaller scale. This sounds great on paper, but there are several major problems in both theory and practice. Simons and Mense also emphasize that it has “not been firmly established” that stretching trigger points is helpful, and that stretch works primarily for “newly activated, single-muscle” trigger points … leaving out a lot of trigger points that are serious problems. There are many circumstances in which you can not realistically hope to win a tug-of-war with a strong one, because it would be too anatomically awkward and/or too painful.

How can we pull apart a powerful contraction knot — a tiny segment of muscle fibres in full spasm — with anything less than pliers, a vice, and a glass of bourbon? We almost certainly do not have the leverage or pain tolerance required, especially if the muscle fights back with a defensive contraction (which may account for the cases that backfire). That trigger point is like a knot in a bungie cord: all we’re going to to do is stretch the hell out of the bungie cord on either side of the knot. If it works at all, it probably mostly only works on the milder cases that don’t matter much in the first place.

And then there’s the possibility that Simons and Mense were just wrong, and a trigger point is not like a tiny cramp at all. If there is no metabolic “revving,” no energy crisis to interrupt by pulling muscle proteins apart like kids fighting on a playground, then it’s back to the drawing board: either stretching doesn’t work at all, or we just have no idea how it works. Which is possible.

For more detail on this topic, see:

“But don’t people just need to be taught how to stretch properly?”

No one actually knows what a “proper” stretch is. There are no accepted standards in stretching technique (not even close), no method that is clearly superior, no way to know what’s right, no definition of success and no accepted method of achieving it.

The pretentious subtext of all preaching about stretching technique is always the same: stretching is only valuable if you “know what you’re doing.” And so a number of experts stay in business by advocating a stretching method or rationale that seems to trump all the others. Unfortunately, none of them can agree with each other.

The nice thing about standards is that there are so many of them to choose from.

~ Andrew S. Tanenbaum

Here is a vivid example of the problem. This is an excerpt from one of my text books, a weighty and authoritative tome, a bible of therapeutic exercise:

Several authors have suggested that a period of 20 minutes or longer is necessary for a stretch to be effective and increase range of motion when a low-intensity prolonged mechanical stretch is used.

three citations listed, Therapeutic Exercise, 3rd Ed., Kisner/Colby, p157

Twenty minutes? Almost no one is stretching for that long. No one’s recommending that. And yet “several authors” have found that it is “necessary.” So it would seem to be a “correct” method of stretching, yet it is absent from professional wisdom on the subject … because, of course, it is contradicted in other text books, by other experts, not to mention the fact that it’s extremely impractical. Imagine trying to stretch for injury prevention: 20 minutes for each of even just 10 important muscles would be more than three hours.

The idea of proper stretch technique is mostly a fantasy.

“But isn’t yoga all about stretching? And Yoga has lots of benefits, doesn’t it?”

Yes, it is, and yes, it does — but probably not the benefits that people normally attribute to stretching. Even flexibility is suspect.44 Same with qigong, and the martial arts are full of stretching techniques — some of them appropriated from the modern Western fitness tradition, and others inherited from traditional practices. I advocate this kind of stretching elsewhere in my writings. So what’s the difference?

The difference is in intention. The intention of stretching in the context of good qigong, yoga or martial arts is to focus the mind, to stimulate vitality through a combination of mental and physical exercise. The intention is everything — without the intention, you might as well not bother with these activities.

Most westerners stretch without the foggiest notion of this underlying complexity. Stretching is generally stimulating to body awareness, of course: but that awareness is unsophisticated and incidental, rarely involving any insight more complex than “ooh, that muscle sure is sore.” Without education about intent — without a rich philosophical context — the value of stretching in yoga is just as uncertain as it is in any other situation.

And stretching in yoga also involves some risks. Too often people perceive yoga as an entirely wholesome and harmless activity, but in fact over-stretching injuries and muscle strains are actually common. As with dancing or martial arts, there are many ways to hurt yourself practicing yoga.

The unstretchables: the many muscles that are biomechanically impossible to stretch

Another significant practical difficulty with stretching that never gets discussed: there are several important muscles and muscle groups that are mechanically impossible to stretch, including ones (like the quadriceps) that people think they are stretching. Even if stretching actually had the benefits that people want to attribute to it — which it clearly does not — those benefits would still not actually be available in large sections of the body. See:

The Unstretchables: Eleven muscles you can’t actually stretch hard (but wish you could)

Is stretching good for tendons? Can it align their fibres?

Muscle and tendon, although they are distinct tissues, blend together quite seamlessly. Much of what we think of as mucle is an extension of tendinous tissue, and vice versa. It’s impossible to draw a line where tendon stops and muscle starts, and if stretching doesn’t do much to muscles, it probably doesn’t do much to tendons either.

And so most likely a positive effect of stretching on tendons is minimal or nil. Digging a little deeper…

In general, tissues are stimulated to growth and repair by the same forces that they normally have to deal with (and also the same forces that occasionally overload and overwhelm them and cause overuse injury or trauma). That stimulus is dished up far more efficiently and thoroughly by normal (and athletic) activity than by any isolated deliberate exercise therapy.

Cells inside of tendons generate collagenous fibres and absorb others as needed in response to stresses, constantly remodelling and tweaking the tendon so that it is optimized to cope with the actual stresses it encounters all day, every day. (Organisms always act on the assumption that the immediate future will probably be similar to the immediate past — that doesn’t always work out, but it’s a pretty good rule of thumb.)

However, tendons are quite static compared to other tissues, and remodelling is slow and “conservative” — they don’t do it quickly. Even a very strong stretch to a tendon constitutes an extremely brief input of stimulus relative to the context of an entire day or week of normal usage of the tendon. It probably takes months of regular, consistent, and significant new stresses for a tendon to change.

For comparison, consider how bone remodels — and bone is much more dynamic and responsive than tendons are. If bones are subjected to strong new stresses, they will change, slowly but steadily getting thicker and tougher in just the right way to cope with that stress. But it takes a lot! Now, how much do you suppose you could influence that process by deliberately applying a force to the bone? Even a fairly heroic twenty-minute application per day — far more than anyone would ever bother stretching a single tendon, or pair of tendons? And even if it could work, what are the chances that the deliberate application of force would be a good enough “simulation” of natural biomechanical stresses that it would elicit the desired, relevant adaptation? A simulation might be good enough in principle in some cases, but in general it’s just not going really be very much like the stresses that the tendon actually has to deal with in the real world — and therefore fundamentally inefficient way of preparing for it! If it works at all.

About alignment … the specific notion that tendon stretching will “align” its fibres is a particularly dubious and overly optimistic concept. Tendons are well nigh impervious, rupture only with extreme forces (and/or when already compromised), and change only in response to long term “just right” overloading. It’s relevant to understand that they are so tough that they are the strongest link in the chain, and in many cases they will tear away from their moorings on bone (avulsion fracture) before the “rope” breaks. For a mere stretch, collagen fibres don’t line up obediently any more than they already are — and tendons have impressively well-aligned microscopic orderliness to begin with.

It’s also extremely important to note that study after study after study has shown no injury prevention benefit to stretching — as covered above — and that includes tendon injuries. Tendons are not getting injured any less frequently in people who stretch a lot. If you want to reduce the chances of your tendons rupturing, then the way to do it is to expose them to a bunch of activities. Push the envelope just a little: enough that they are challenged, but not brutalized! Just the right amount of stimulation.

Scratching your inner itch: a feel-good theory

Is food an effective therapy because it tastes good?

Is music an effective therapy because it sounds good?

Essentially every pleasant sensation and experience has therapeutic qualities. These therapeutic qualities are not unimportant, but they’re not the same thing as an effective therapy. There’s a good reason why your physical therapist never prescribes ice cream. Here’s the last big stretching mystery I’d like to cover: how can stretching be so pleasant without (apparently) doing much measurable good? Look at this pattern:

  • Stretching feels great … but it’s over-rated and nowhere near as medically or athletically useful as most people think.
  • Massage feels even better … but its effects on pain are notoriously mild and fleeting.
  • Chiropractic “adjustments” can feel scrumptious, even addictive, especially in that cinder-block-rigid area between the shoulder blades … but in most cases you’ll be craving a re-do before long (which makes for a lovely business model for chiropractors).

The pattern is that of being “relieved” instead of “fixed.” Over many years of thinking about pain and therapy, it has been a stubborn mystery to me why these things can feel so good — really, really good — without making any large or lasting difference to most painful problems, most of the time.

Feeling good without working all that well causes no end of confusion and trouble. Wonderful and profound sensations are largely responsible for an epidemic of excessive optimism about their healing powers. It’s understandable that we would expect something that feels that good to work well, but a lot of testing has shown over and over again that stretching, massage and chiropractic are not exactly saving the world from its aches and pains.

It’s not hard to explain how something might feel good without curing pain. Sex feels great, but it does not cure pain. Back scratches, chocolate cake, sunshine, and hot baths: all wonderful, all mostly powerless to cure pain.

But stretching is where the gap between how it feels and how well it works is the most glaring, the best feeling but most useless of “treatments.” I’ve already mentioned that I do stretch regularly because I like it, but that doesn’t quite cover it: I actually stretch for pleasure almost every single day. I’m as inflexible and prone to aches and pains as ever, and I’ve never been able to justify the habit with anything except, “Because it feels good, dammit.” And that’s fine.

But why does it feel that good? “It’s stimulating” just doesn’t cut it. I can give a specific reason why each of the delicious things above feel so good. But stretching? I just don’t get it.

And then one day — while I was stretching, of course — I had an epiphany: stretching doesn’t just feel like scratching an itch, maybe it’s actually scratching an itch. A deep itch. In my experience, stretching feels best when I am sore from working out — which only deepens the mystery. Why would it feel so pleasant to pull on soft tissues that are incredibly sore?

That soreness is like an internal “rash” or any skin irritation. And we feel an incredible compulsion to scratch rashes, mosquito bites and other itchy, irritated things. Consider the mosquito bite: scratching it is certainly not going to “treat” it, and we know it. But the temporary relief of scratching is so great it almost transcends pleasure and degenerates into a nasty compulsion. As many pleasures do.

Could it be that exercise-induced soreness is kind of like a minor internal “rash”? And that stretching is just about as close as we can get to “scratching” it? To get a little fleeting relief? This is the best analogy I’ve come up with yet to describe how stretching feels to me.

There may be many reasons why stretching feels good without being particularly helpful, but this makes some serious sense to me. It’s specific and plausible. It achieves the difficult trick of simultaneously accounting for both the unusually pleasant sensation and the more or less total lack of any meaningful effect. And it nicely fits the way I like stretch best when my muscles feel the worst. And it makes even more sense if you extend the metaphor of the itch to include the even more common sensations of being stuck or stagnant, which I’ve written about in the past (guest posting for Todd Hargrove’s excellent blog, see The Bamboo Cage).

I have often said that stretching and other relieving sensations of massage or spinal adjustment feel “like” scratching an itch. But I never went that extra step and considered that maybe they feel like that because, in a way, they actually are — because we can have genuine internal “itches,” vague sensory annoyances … and very limited and indirect ways of scratching them.

Part 4

Back to the question of flexibility

There is really only one stretching benefit that seems to be clear and (almost) uncontroversial: it does increase flexibility. For whatever it’s worth, people do seem to be more flexible when they stretch regularly for a while. It’s not easy to achieve, but it can be done. The phenomenon is widely observed, and has been confirmed by experiments. I previously cited Marshall et al — a decent and recent example — and there are certainly others.

But what is it worth? Is it actually a benefit? I’ve already argued that is not, but to make the case more effectively, it’s important to study the nature of flexibility. When someone increases their flexibility, what changes, exactly? How does it work?

Probably not by actually making tissue “longer”…

The last theory standing: tolerance

Several explanations for increased flexibility from stretching have been proposed, and none have panned out. A 2010 paper in Physical Therapy reviews them all in great detail, and the full text is free.45 It’s not light reading, but there are some fascinating highlights. For instance, the authors torpedo the popular theory that muscles actually change length (“plastic deformation”):

In 10 studies that suggested plastic, permanent, or lasting deformation of connective tissue as a factor for increased muscle extensibility, none of the cited evidence was found to support this classic model of plastic deformation.

After reviewing several more disproven popular theories, they get to the good part: the last theory standing.

Increases in muscle extensibility observed immediately after stretching and after short-term (3 to 8-week) stretching programs are due to an alteration of sensation only and not to an increase in muscle length. This theory is referred to as the sensory theory throughout this article because the change in subjects’ perception of sensation is the only current explanation for these results.

Note the very interesting phrasing, “the only current explanation.” That’s a Sherlock Holmesian way of putting it: “Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth.” It’s a strange, cool, and unexpected conclusion … but it’s also all we’ve got left, so we should probably take it seriously.

Of course, no debate is ever really over, and scientific evidence continues to accumulate. But stretch tolerance probably has a lot to do with flexibility gains.

Increased flexibility may simply be an increased tolerance for the discomfort of excessive muscle elongation.

Let’s get neurological

If you do some upper body stretching, your lower will get a little more flexible. Not much, but enough to measure in a controlled test.46 But that’s the only effect — which suggests that it’s due to an increase in tolerance of stretch, and that’s all. It’s one of many clues suggesting that stretch tolerance is the secret sauce in flexibility.

In other words, muscle (probably) doesn’t change, especially in response to an average stretching regimen… but our willingness to elongate it probably does. This is clearly supported by some research.47

Stretching is a way of teaching the nervous system that it’s okay to stretch a little further.

If so, then elongation must normally be limited by a strict neurological edict. The brain and spinal cord decree: you’re only going to lengthen your muscles so far, period, end of discussion. It’s not a negotiation … at least not in the short term. Don’t make the mistake of thinking you could just blast through that barrier with will power.

There is a strong analogy here to strength: we always have much greater muscle power available than we can safely use. We have deep reserves that are literally impossible to tap into on short notice, without large squirts of adrenalin. Contractions are normally reined in by the brain. Even with a powerful grunt of effort, only a small fraction of your muscle fibres get a signal to contract at any one time. If you recruited all of them, you might rip the muscle off your bones, or at least completely exhaust yourself in seconds. Your central nervous system has excellent reasons for imposing a power limit. Full contraction is for dramatic, obvious, life and death situations only.

However, with training, we can learn to recruit more fibres. In fact, when people train their muscles, early strength gains may be mainly a matter of learning to “recruit” more muscle fibres at once.

Here’s an interesting example from science of how increasing flexibility may be more of a nervous system “hack” than a matter of changing tissue. It appears that if you just add some vibration, even already flexible gymnasts can get a surprising boost in flexibility.484950 Clearly that is a neurological effect on flexibility … and a very cool one.

Despite all of the above, Team Plasticity remains large and devout: many professionals still believe that tissues adapt their structure to stretching. They can point to some research to support that position. The 2011 study of flexibility I cited above is great example (Marshall et al). It clearly showed that stretching increases flexibility: when subjects were stretched with the same force (torque) applied, pushed to the same level of discomfort, they could go 20% farther. So we know something changed! But … what? Was is a change in tissue? Or tolerance?

This data doesn’t say. But the authors seemed to think it did. They followed their data into an overinterpretation, presumably trying to score points for Team Plasticity. Because range increased, but pain at the end of the range did not, they unwisely concluded that a change in tolerance was not a factor.51 But stretching farther without hurting more could mean an increase in (neurological) tolerance! Although it wasn’t measured, it’s safe to assume the subjects’ pain would have been less if stretched only to the end of their original range.

This experiment was agnostic about mechanism. It cannot actually settle the bet — it demonstrated only a reduction in stiffness, but not whether it was due to neural or structural adaptations. And that’s the problem with the research as a whole: plasticity has almost been ruled out by a bunch of studies — here’s another fresh one52 — but not completely, and meanwhile neurological adaptation still hasn’t been confirmed.

Body is not stiff, mind is stiff.

~ K. Pattabhi Jois

The wisdom of the body

As with contraction, your body probably has excellent reasons for strictly limiting elongation. When a stretch becomes uncomfortable, that’s your nervous system saying, “No way, sister, we don’t go there — we’ve got some sensible rules about this.”

And you really just can’t overrule your spinal cord on this. Talk about wisdom of the body!

But apparently we can get used to stretching — we can learn to tolerate greater elongation to some extent. Fascinating! This goes a long way to explaining the flexibility feats of yogis and martial artists, whose hypermobility might well be dangerously dysfunctional if it were attributable to plastic deformation. Plastic deformation simply does not occur in the most athletes, and maybe none. It might occur at the extremes of flexibility performance, but only so much — if you actually deformed your muscles and tendons enough to really preztel yourself, they would probably also be too loose to be useful the rest of the time.

It’s a tidy, attractive theory that plastic deformation is minimal, and contortionism largely powered by extremes of stretch tolerance — they have trained themselves to allow their latent capacity for full muscular elongation, but their muscles retain the ability to return to a normal length.

Stretching for contracture: Thumbs down to static stretching as a treatment for seizing up

“Contracture” is the unlovely process of muscle and other soft tissues seizing up in response to neurological problems or prolonged immobilization. Your face can’t really “freeze like that” as your mother warned you, but if you could make an ugly face long enough — weeks — eventually contracture really would set in. This is pathology, mind. The tissue changes. For the worse.

Most people probably assume that long, intense stretches are an effective prevention/treatment for contracture. It is not an assumption held with much conviction, but stretching always gets the benefit of the doubt, whether it deserves it or not, and it seems to make sense that stretching would be a cure for contracture.

Common sense fails again. As it so often does. The Cochrane Collaboration published a review of static stretch for the treatment and prevention of contractures.53 The verdict? Thumbs way down. Based on “high quality evidence” they concluded that “stretch is not effective for the treatment and prevention of contractures.” I’m shocked. Shocked, I say!

So this is (yet another) great example of a “technical” reason to stretch that many or most people would assume to be effective. But no — probably not static stretch, anyway.54

Pathologically seized up tissue cannot be meaningfully elongated. So what’s happening when healthy people seem to get flexible?

Part 5

So stretching is good for … stretching?

That’s a reasonably safe theory about how flexibility works. But it is not easy to achieve significant stretch tolerance — it takes weeks of diligent effort, quite a bit more than most people ever actually push themselves to achieve. Many people probably believe that they have achieved this, but it’s mostly wishful thinking, and the huge majority have only scratched the surface of their potential flexibility during brief phases of their lives.

More to the point, what’s the point? We already know that stretching does not do all the basic stuff we used to hope it was doing, especially injury prevention. Is it good for anything else?

There is no known benefit to greater flexibility, except for:

  • bragging rights
  • dominating Twister tournaments
  • making full use of Indian love manuals

In short, stretching appears to be good for … more stretching. Oh, and of course:

  • yes, stretching does feel pleasant

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 ScienceBasedMedicine.org 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.

Part 6

Appendices

More reading

Other interesting reading relevant to stretching:

What’s new in this article?

This article had a long history of unlogged updates — a decade or so — before I finally started logging them in 2015.

FebruaryExpanded: Added more the nature of soreness and stiffness, and the relevance of stretching (or lack thereof). [Section: “But I find that stretching helps my aches and pains…”.]

FebruaryMinor addition: “Endorphins” now have a sidebar. [Section: So if all that’s true, then why is it that I feel like I have to stretch or I’m going to seize up like an old piece of leather? Why do I have this compulsion to stretch, and why does it feel so good, if it’s not actually doing anything?]

2017Science update: Cited Blazevich et al on tolerance of calf stretching. [Section: Let’s get neurological.]

2017New section: Discussion of four ways that stretching may cause harm, especially for medically vulnerable people. [Section: Stretching can cause injuries.]

2017Science update: Added preliminary discussion of evidence on the prevention of muscle strains. (More to come on this topic.) [Section: Stretching research shows that stretching does not prevent injury.]

2017Science update: Cited and discussed implications of anti-inflammatory effect reported by Berrueta et al. [Section: “But I find that stretching helps my aches and pains…”.]

2017Revised: A heavy edit for clarity and brevity. [Section: Stretching research shows that stretching does not prevent exercise soreness.]

2016Rewritten: Complex and thorough modernization and other improvements. [Section: “But I find that stretching helps my aches and pains…”.]

2016Revised: Reorganized the list of reasons for stretching, officially including “it feels good.” Updated the summary of stretching for trigger points. [Section: Why people stretch: the five most popular reasons.]

2015Upgrade: Added table of contents.

Notes

  1. Cooper, Bob. “The Rules Revisited.” Runner’s World. September, 2009. p. 59. BACK TO TEXT
  2. Shrier I. Stretching before exercise does not reduce the risk of local muscle injury: a critical review of the clinical and basic science literature. Clin J Sport Med. 1999;9. PubMed #10593217.

    This paper and Herbert are literature reviews: that is, they are reviews of many other studies. They both show many contradictions in existing research, but they both conclude that there is no convincing evidence that stretching is useful.

    BACK TO TEXT
  3. Herbert RD, Gabriel M. Effects of stretching before and after exercising on muscle soreness and risk of injury: systematic review. BMJ. 2002 Aug;325(7362):468. PainSci #57209. BACK TO TEXT
  4. Pope RP, Herbert RD, Kirwan JD, et al. A randomized trial of preexercise stretching for prevention of lower-limb injury. Medicine Science in Sports Exercise. 2000 Feb;32(2):271–7. PubMed #10694106.

    Several hundred army recruits stretched before every training workout for 12 weeks: “one 20-s static stretch under supervision for each of six major leg muscle groups during every warm-up.” Their injuries were compared to hundreds more who didn’t stretch. The authors of the study concluded that “typical stretching does not produce clinically meaningful reductions in risk of exercise-related injury in army recruits.”

    BACK TO TEXT
  5. Tip of the hat to reader Jennifer M, who sent me this. Jennifer added that this passage reminded her of her father, “who remained competitive at the 800m until into his 60s, but could never come close to touching his toes.” Good example! BACK TO TEXT
  6. I spent a decade in clinical practice as a massage therapist, routinely asking my patients about their stretching beliefs and habits, among many other things. These days I am a full-time writer on these topics with a global audience, so I heard vastly more about stretching from readers by email than I ever heard from my patients back in the day. I have a great bird’s eye view of popular opinions about stretch. Professionals send me a lot of mail as well, so I get a lot of exposure to their opinion’s. Are they more educated about stretch? You’d sure hope so, but that hasn’t really been my impression, to be honest — it really seems like everyone is just repeating things they heard other people say. Professionals just hear and repeat even more. BACK TO TEXT
  7. Flexibility is routinely suggested both as a reason to stretch, and a reason why stretch works for other purposes. These are quite different things. Both will be considered in detail below. BACK TO TEXT
  8. More evidence on this is coming, but meanwhile there’s an interesting general principle at work here that is worth pointing out: these goals are proven to be impossible either straightforwardly by an evidence of absence, or less obviously but almost as certainly by a preponderance of evidence of minor efficacy. Proof of the existence of a trivial benefit damns with faint praise, and proving that something barely works is literally almost the same as proving that it doesn’t work at all. This is chronic problem with many allegedly effective treatments and therapies: they may work a little, but they fail to impress. Stretching suffers from this problem in spades. BACK TO TEXT
  9. Most people put no more thought put into it than they do when scratching an itch, but most who think about it assume that the point is to treat “muscle knots” (trigger points). It might be, but trigger points are theoretical and controversial, and there are major practical problems with stretching them in any case. BACK TO TEXT
  10. Azevedo DC, Melo RM, Alves Corrêa RV, Chalmers G. Uninvolved versus target muscle contraction during contract: relax proprioceptive neuromuscular facilitation stretching. Phys Ther Sport. 2011 Aug;12(3):117–21. PubMed #21802037. BACK TO TEXT
  11. Kay AD, Blazevich AJ. Effect of Acute Static Stretch on Maximal Muscle Performance: A Systematic Review. Med Sci Sports Exerc. 2011 Jun 8. PubMed #21659901. Researchers looked at more than 4500 studies before choosing about 100 to look at more carefully. The found “overwhelming evidence” of “no significant effect,” and that is certainly no surprise for anyone who had been watching stretching science over the years. BACK TO TEXT
  12. Damasceno MV, Duarte M, Pasqua LA, et al. Static Stretching Alters Neuromuscular Function and Pacing Strategy, but Not Performance during a 3-Km Running Time-Trial. PLoS One. 2014;9(6):e99238. PubMed #24905918. PainSci #53972. The conclusion reproduces and builds on similar evidence. It wasn’t a huge negative effect, but absolutely in the wrong direction! An epic fail for stretching. BACK TO TEXT
  13. Lowery RP, Joy JM, Brown LE, et al. Effects of static stretching on 1-mile uphill run performance. J Strength Cond Res. 2014 Jan;28(1):161–7. PubMed #23588487.

    There’s more to say about this one, and Alex Hutchinson did, but here’s the nasty nugget: pre-run stretching caused an eight percent drop in performance in a one-mile uphill run. Yikes!

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  14. Soligard T, Myklebust G, Steffen K, et al. Comprehensive warm-up programme to prevent injuries in young female footballers: cluster randomised controlled trial. BMJ. 2008;337:a2469. PubMed #19066253. PainSci #56160. In 2008, Norwegian researchers compared injuries in over a thousand female footballers who participated in such a warmup for a season, to another several hundred who didn’t. The athletes with the warmup had fewer traumatic injuries, fewer overuse injuries, and the injuries they did have were less severe. Static stretching was not part of the warmup. “Active stretching” was … but “active stretching” is what I would call “mobilizations” — doing moving lunges, for instance — as opposed to the kind of static or passive stretching that most people think of when they think of stretching. BACK TO TEXT
  15. Soligard T, Nilstad A, Steffen K, et al. Compliance with a comprehensive warm-up programme to prevent injuries in youth football. Br J Sports Med. 2010 Sep;44(11):787–93. PubMed #20551159. PainSci #54998.

    Researchers found that injury rates were significantly lower in soccer (football) teams that diligently performed warmup exercises (“The 11+”, a warmup program recommended by FIFA, which notably does not include stretching). On the one hand, there was not much difference between a little warming up (low participation) and a bit more warming up (average participation). But players and teams that did an especially good job of warming up (“twice as many injury prevention sessions”) got solid results: “the risk of overall and acute injuries was reduced by more than a third among players with high compliance compared with players with intermediate compliance.” That extra enthusiasm went a long way!

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  16. A related example

    When I was studying to become a massage therapist, our most scientifically literate instructor dared to share a recent research paper with the class (something no other instructor ever did, which is an ugly truth about my training). The study suggested that massage therapy has no effect on the phenomenon of delayed-onset muscle soreness (Tiidus). This was heretical! Most of the class reacted angrily to this attempt to tip over one the sacred cows of massage therapy, and the hapless instructor was nearly shouted out of the classroom.

    What amazed me most about that was that the belief the students were defending was new to them, based only on what they’d heard from instructors in their first year of classes. And yet it was already essential to their self-image as budding health professionals, a “fact” that they planned to use to promote their services someday. It doesn’t take much for dogma to settle in!

    This incident made quite an impression on me, and is partly responsible for my own journey from credulity to skepticism.

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  17. Berrueta L, Muskaj I, Olenich S, et al. Stretching Impacts Inflammation Resolution in Connective Tissue. J Cell Physiol. 2016 Jul;231(7):1621–7. PubMed #26588184. PainSci #52915.

    In a previous experiment, these researchers claim to have found evidence that stretching successfully treated inflammation and pain in rats. In this follow-up experiment, they looked more closely at the biology, measuring markers of inflammation: inflammatory lesion thickness, neutrophil count, resolvin (RvD1) concentration. They believe this shows a “direct mechanical impact of stretching on inflammation-regulation mechanisms within connective tissue.” It’s intriguing science for sure, but replication in humans is needed before we get too excited about it.

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  18. It’s just one study. We don’t actually know that what Berrueta et al found is for real, and we won’t know until it has been replicated. More importantly, this was a demonstration of an effect on connective tissue, not muscle — and while muscle is full of connective tissue, DOMS is much more of an issue with muscle than connective tissue, and it is far from guaranteed that an effect on connective tissue has anything to do with DOMS. BACK TO TEXT
  19. Lund H, et al. The effect of passive stretching on delayed onset muscle soreness, and other detrimental effects following eccentric exercise. Scand J Med Sci Sports. 1998 Aug;8(4):216–21. PubMed #9764443.

    From the abstract: “There was no difference in the reported variables between experiments one and two. It is concluded that passive stretching did not have any significant influence on increased plasma-CK, muscle pain, muscle strength and the PCr/P(i) ratio, indicating that passive stretching after eccentric exercise cannot prevent secondary pathological alterations.”

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  20. Cheung K, Hume P, Maxwell L. Delayed onset muscle soreness: treatment strategies and performance factors. Sports Med. 2003;33(2):145–64. PubMed #12617692.

    From the abstract: “Cryotherapy, stretching, homeopathy, ultrasound and electrical current modalities have demonstrated no effect on the alleviation of muscle soreness or other DOMS symptoms.”

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  21. Weber MD, Serevedio FJ, Woodall WR. The Effects of Three Modalities on Delayed Onset Muscle Soreness. Journal of Orthopaedic & Sports Physical Therapy. 1994;20(5):236–42. PubMed #9512831.

    From the abstract: “… analysis indicated no statistically significant differences between massage, microcurrent electrical stimulation, upper body ergometry, and control groups.”

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  22. Herbert RD, de Noronha M, Kamper SJ. Stretching to prevent or reduce muscle soreness after exercise. Cochrane Database Syst Rev. 2011;(7):CD004577. PubMed #21735398.

    Does stretching help either before or after exercise to reduce soreness? Nope. This large review of eleven small scientific studies, and one huge one, wrapped up with a clear thumbs down:

    The evidence from randomised studies suggests that muscle stretching, whether conducted before, after, or before and after exercise, does not produce clinically important reductions in delayed-onset muscle soreness in healthy adults.

    The evidence was “low to moderate,” with “moderate to high” risk of bias, which means most of the researchers were probably hoping to find that stretching does help DOMS…but even with that likely bias, they still didn’t find what they were looking for.

    The big study was technically positive, finding an average drop in soreness of four points on a 100-point scale, which is basically meaningless. The variation between the results for individuals is undoubtedly greater than that.

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  23. Hart L. Effect of stretching on sport injury risk: a review. Clin J Sport Med. 2005 Mar;15(2):113–113. PubMed #15782063.

    ABSTRACT


    OBJECTIVE: Effect of Stretching on Sport Injury Risk: a Review To assess the evidence for the effectiveness of stretching for the prevention of injuries in sports.

    DATA SOURCES: MEDLINE (1966 to September, 2002), Current Contents, Biomedical Collection, Dissertation Abstracts, the Cochrane Library, and SPORTDiscus were searched for articles in all languages using terms including stretching, flexibility, injury, epidemiology, and injury prevention. Reference lists were searched and experts contacted for further relevant studies.

    STUDY SELECTION: Criteria for inclusion were randomized trials or cohort studies of interventions that included stretching compared with other interventions, with participants who were engaged in sporting or fitness activities. One author identified 361 articles reporting on flexibility, methods and effects of stretching, risk factors for injury, and injury prevention, of which 6 articles fulfilled the inclusion criteria for meta-analysis.

    DATA EXTRACTION: Three independent reviewers blinded to the authors and institutions of the investigations assessed the methodologic quality of the studies (100-point scale) and reached consensus on disagreements. Details of study participants, interventions, and outcomes were extracted. Weighted pooled odds ratios were calculated for effects of interventions on an intention-to-treat basis.

    MAIN RESULTS: Reduction in total injuries (shin splints, tibial stress reaction, sprains/strains, and lower-extremity and -limb injuries) with either stretching of specific leg-muscle groups or multiple muscle groups was not found in 5 controlled studies (odds ratio [OR] 0.93; 95% CI, 0.78 to 1.11). Reduction in injuries was not significantly greater for stretching of specific muscles (OR, 0.80; CI, 0.54-1.14) or multiple muscle groups (OR, 0.96; CI, 0.71-1.28). Combining the 3 ratings of methodologic quality, median scores were 29 to 60/100. After adjustment for confounders, low quality studies did not show a greater reduction in injuries with stretching (OR, 0.88; CI, 0.67-1.15) compared with high quality studies (OR, 0.97; CI, 0.77-1.22). Stretching to improve flexibility, adverse effects of stretching, and effects of warm up were not assessed by appropriate intervention studies.

    CONCLUSION: Limited evidence showed stretching had no effect in reducing injuries.

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  24. Brushøj C, Larsen K, Albrecht-Beste E, et al. Prevention of overuse injuries by a concurrent exercise program in subjects exposed to an increase in training load: a randomized controlled trial of 1020 army recruits. Am J Sports Med. 2008 Apr;36(4):663–670. PubMed #18337359. BACK TO TEXT
  25. Pereles D, Roth A, Thompson DJ. A Large, Randomized, Prospective Study of the Impact of a Pre-Run Stretch on the Risk of Injury in Teenage and Older Runners. USATF.org. 2011 Jun 15. PainSci #55243. BACK TO TEXT
  26. Lauersen JB, Bertelsen DM, Andersen LB. The effectiveness of exercise interventions to prevent sports injuries: a systematic review and meta-analysis of randomised controlled trials. Br J Sports Med. 2014 Jun;48(11):871–7. PubMed #24100287. PainSci #53226. BACK TO TEXT
  27. They thought strengthening looked good, but based their very positive-sounding conclusions on only four studies of dubious quality and relevance. BACK TO TEXT
  28. Behm DG, Blazevich AJ, Kay AD, McHugh M. Acute effects of muscle stretching on physical performance, range of motion, and injury incidence in healthy active individuals: a systematic review. Appl Physiol Nutr Metab. 2016 Jan;41(1):1–11. PubMed #26642915. PainSci #52916.

    This wide-ranging review concluded that “studies indicate a 54% risk reduction in acute muscle injuries associated with stretching.” This is at odds even with previous reviews by some of the same key authors. For instance, while McHugh et al were optimistic in 2010, they based their optimism on speculation and characterized the evidence as limited: “For example, there is a good rationale for why stretching could impact the risk of sustaining a muscle strain injury, but the effect of stretching on muscle strain injuries has not been adequately researched in sports with a high incidence of muscle strains.” That was just six years prior, with almost no relevant new evidence in the interim.

    Nearly identical evidence. One review calls it inadequate. The other says stretching prevents muscle strain.

    So I guess this question is not settled. 😜

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  29. For instance, if stretching reduces the chances of tearing a muscle, you’d need to stretch the muscles most likely to tear, which are the big muscles of the thighs: quadriceps, hamstrings, and adductors (groin). Hamstrings are likely to be included in most stretching regimens. Quadriceps are often included, but not always. Adductors are often missed or given minimal attention. If stretching reduces the risk of muscle strains, you’d have to make a point of stretching all three — and that’s only the most common strain locations. BACK TO TEXT
  30. HSD is a bucket diagnosis for people with symptomatic hypermobility, but without a clear diagnosis of a connective tissue disorder, like EDS or Marfan syndrome. BACK TO TEXT
  31. “The essential difference between HSD and hEDS lies in the stricter criteria for hEDS compared to the HSD.” But it’s very tricky, and those criteria all very new (see the 2017 EDS International Classification). Ironically, as of 2017, the one sub-type of EDS that does not have an identified genetic cause is the hypermobile EDS (hEDS). BACK TO TEXT
  32. Scheper MC, de Vries JE, Verbunt J, Engelbert RH. Chronic pain in hypermobility syndrome and Ehlers-Danlos syndrome (hypermobility type): it is a challenge. J Pain Res. 2015;8:591–601. PubMed #26316810. PainSci #52758. Hypermobility is “highly prevalent among patients diagnosed with chronic pain.” BACK TO TEXT
  33. Marshall PW, Cashman A, Cheema BS. A randomized controlled trial for the effect of passive stretching on measures of hamstring extensibility, passive stiffness, strength, and stretch tolerance. J Sci Med Sport. 2011 Nov;14(6):535–40. PubMed #21636321. BACK TO TEXT
  34. From Kay et al: “The detrimental effects of static stretch are mainly limited to longer durations (≥60 s) which may not be typically used during pre-exercise routines in clinical, healthy or athletic populations. Shorter durations of stretch (<60 s) can be performed in a pre-exercise routine without compromising maximal muscle performance.” BACK TO TEXT
  35. Beckett JR, Schneiker KT, Wallman KE, Dawson BT, Guelfi KJ. Effects of Static Stretching on Repeated Sprint and Change of Direction Performance. Medicine & Science in Sports & Exercise. 2009 Jan 5. BACK TO TEXT
  36. The most obvious wrinkle is that the negative impact of static stretching on sprinting might be short term — were the runners slowed down for only ten minutes? Twenty minutes? As much as sixty? Another important consideration is that the potential therapeutic effects of stretching — still remarkably unproven at this late date in history, but still hypothetically possible — could conceivably outweigh the relatively small cost of being slowed down. For instance, if (big if) stretching significantly reduced the risk of a muscle strain, would that risk reduction be worth the cost to sprinting speed? Probably! If. BACK TO TEXT
  37. Farinatti PT, Brandão C, Soares PP, Duarte AF. Acute effects of stretching exercise on the heart rate variability in subjects with low flexibility levels. J Strength Cond Res. 2011 Jun;25(6):1579–85. PubMed #21386722.

    … multiple-set flexibility training session enhanced the vagal modulation and sympathovagal balance in the acute postexercise recovery, at least in subjects with low flexibility levels. … The present results suggest that stretching routines may contribute to a favorable autonomic activity change in untrained subjects.

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  38. Ylinen J, Kautiainen H, Wiren K, Hakkinen A. Stretching exercises vs manual therapy in treatment of chronic neck pain: a randomized, controlled cross-over trial. J Rehabil Med. 2007;39(2):126–132. PubMed #17351694.

    This examiner-blinded randomized cross-over trial of 125 patients found pretty promising benefits to both stretching exercises and “manual therapy” for a month, and the researchers concluded that “low-cost stretching exercises can be recommended in the first instance as an appropriate therapy intervention to relieve pain, at least in the short-term.” However, there are several reasons not to get too excited about the significance of this study, perhaps the most important of which is simply that showing some improvement over 4 weeks is hardly an impressive therapeutic accomplishment, and if the study had included a control group it might well have revealed that the “therapeutic” effects weren’t much different than the natural course of the condition — i.e. everyone might have gotten better, with and without therapy of any kind.

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  39. Sherman KJ, Cherkin DC, Wellman RD, et al. A Randomized Trial Comparing Yoga, Stretching, and a Self-care Book for Chronic Low Back Pain. Arch Intern Med. 2011 Oct. PubMed #22025101.

    This experiment compared the effects of yoga, a normal stretching class, and an educational booklet on chronic low back pain. The primary findings were that both yoga and stretching seemed to be modestly effective, but neither was better than the other. Back in 2005, the same authors got similar results comparing yoga to conventional therapeutic exercise.

    The research has been widely reported as “stretching and yoga work,” with a few writers emphasizing that yoga was no better. However, I haven’t seen anyone report that both stretching and yoga are equally damned here with faint praise, and quite possibly illusory praise: the effect size was modest, just 2.5 points on a scale of 11, and some or all that effect may well be attributable to bias an frustrebo (frustrated placebo) caused by a lack of blinding. Subjects deprived of either a lovely stretching or yoga experience may have reported a more negative experience.

    I analyze this study in greater detail in my advanced tutorial, Save Yourself from Low Back Pain!

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  40. Some drugs are notorious for causing joint and/or muscle pain as a side effect. (Other kinds of pain are possible too, but are usually more distinctive and readily identified as a drug side effect. But joint and muscle pain are often mistaken for musculoskeletal trouble, and no one suspects the drug.) The usual suspects are the statins (for lowering cholesterol), bisphosphonates (for osteoporosis and Paget’s disease), fluoroquinolones (a class of antibiotics), the retinoids (for skin conditions, like Accutane for acne), and Trintellix (an antidepressant). Some of these may actually be innocent, others almost certainly do cause trouble: it’s surprisingly unclear, like most of medicine. For more detail on some of them, see Surprising Causes of Pain. BACK TO TEXT
  41. Berrueta 2016, op. cit. BACK TO TEXT
  42. Langevin HM, Stevens-Tuttle D, Fox JR, et al. Ultrasound evidence of altered lumbar connective tissue structure in human subjects with chronic low back pain. BMC Musculoskelet Disord. 2009 Dec;10:151. PubMed #19958536. PainSci #53554.

    Researchers measured the thickness of lumbar connective tissues with ultrasound in 60 chronic low back pain patients and 47 health people. The fascia was about 25% thicker in people with back pain, which is quite a bit, and a surprising finding with potentially major — but unknown — clinical significance. The authors suggest that it could be related to “genetic factors, abnormal movement patterns and chronic inflammation.”

    This observation has not been reproduced by other researchers, but a follow-up study in 2011 examined the flexibility of the same tissue, and found it was about 20% less in back pain pain patients: see Langevin for more commentary on the implications of both studies.

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  43. Many readers have pointed out that experienced yoga practitioners are flexible, especially the older ones. For instance, T.G. writes, “In my yoga class, the older people are way more flexible than the younger ones.” It may be that training has made them more flexible, but not necessarily. A perpetually neglected explanation for the flexible-yoga-oldster phenomenon is that people with natural gifts of flexibility like the activity and stick with it, because we humans enjoy almost anything we’re good at … and the less flexible tend to drop out. I’m not saying this is how it is — I truly don’t know — just that it’s the kind of explanation that tends to get neglected. We need to consider such counter-intuitive, inside-out explanations that are, perhaps, less comforting to our biases. Even if there is a training effect, it’s extremely likely that it’s only part of the reason those folks are more flexible, and that’s something most “huge fans” of stretching have simply never considered. BACK TO TEXT
  44. Weppler CH, Magnusson SP. Increasing muscle extensibility: a matter of increasing length or modifying sensation? Phys Ther. 2010 Mar;90(3):438–49. PubMed #20075147. PainSci #55283. BACK TO TEXT
  45. Behm DG, Cavanaugh T, Quigley P, et al. Acute bouts of upper and lower body static and dynamic stretching increase non-local joint range of motion. Eur J Appl Physiol. 2016 Jan;116(1):241–9. PubMed #26410819.

    In this study, range of motion and strength were tested in the upper body after static stretching in the lower body, and vice versa. Passive range of motion was modestly improved, which is nifty, but not active ROM or strength, suggesting that “enhanced stretch tolerance was likely the significant factor,” as opposed to a mechanical or neural drive mechanism.

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  46. Blazevich AJ, Cannavan D, Waugh CM, et al. Range of motion, neuromechanical, and architectural adaptations to plantar flexor stretch training in humans. J Appl Physiol (1985). 2014 Sep;117(5):452–62. PubMed #24947023.

    For this study, several people stretched their calf muscles twice per day for three weeks (each session consisted of 4 stretches of 30 seconds). They were compared to people who did not stretch. Measurements included changes in muscle and tendon mechanics, muscle activity, and spinal motoneuron excitability. The non-stretchers didn’t change; stretch training “elicited a 19.9% increase in dorsiflexion range of motion (ROM) and a 28% increase in passive joint moment at end ROM.” However, the ROM improvement was not explained by changes in the muscle structure: “Thus, increases in end ROM were underpinned by increases in maximum tolerable passive joint moment (stretch tolerance).

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  47. Issurin VB, Liebermann DG, Tenenbaum G. Effect of vibratory stimulation training on maximal force and flexibility. J Sports Sci. 1994 Dec;12(6):561–6. PubMed #7853452.

    In this 1994 experiment, as described by Sands et al, gymnasts “used a vibrating ring suspended by a cable, in which the foot of the subject was placed while they stretched forward over the raised leg, targeting the hamstrings. The resulting increase in ROM was astonishing. These researchers demonstrated that vibration could enhance flexibility.” The results were replicated by Sands et al in 2006, and Kinser et al in 2008.

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  48. Sands WA, McNeal JR, Stone MH, Russell EM, Jemni M. Flexibility enhancement with vibration: Acute and long-term. Med Sci Sports Exerc. 2006 Apr;38(4):720–5. PubMed #16679989.

    This experiment replicated the results of an intriguing 1994 experiment by Issurin et al. Ten highly trained gymnasts did forward splits with or without vibration. They stretched to the point of discomfort for 4 minutes, alternating between each leg, 10 seconds of stretching at a time. Flexibility immediately after stretching with vibration was dramatically greater; the long-term results were less striking.

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  49. Kinser AM, Ramsey MW, O'Bryant HS, et al. Vibration and stretching effects on flexibility and explosive strength in young gymnasts. Med Sci Sports Exerc. 2008 Jan;40(1):133–40. PubMed #18091012.

    Replicates the findings of both Issurin and Sands — “simultaneous vibration and stretching may greatly increase flexibility, while not altering explosive strength.”

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  50. Several things in the paper suggest their beliefs about the mechanism of increased flexibility, but it’s clearest here: although they concede that they “cannot completely rule out volitional stretch tolerance as a possible explanation for changes in extensibility,” they still conclude that “it does seem that hamstring pain elicited during a passive stretch has little involvement in explaining training related improvements.” Really? Sure seems to me like it could! BACK TO TEXT
  51. Konrad A, Tilp M. Increased range of motion after static stretching is not due to changes in muscle and tendon structures. Clin Biomech (Bristol, Avon). 2014 May 9. PubMed #24856792.

    Another data point in the plasticity vs. tolerance debate: “The increased range of motion could not be explained by the structural changes in the muscle-tendon unit, and was likely due to increased stretch tolerance possibly due to adaptations of nociceptive nerve endings.”

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  52. Harvey LA, Katalinic OM, Herbert RD, et al. Stretch for the treatment and prevention of contractures. Cochrane Database Syst Rev. 2017 Jan;1:CD007455. PubMed #28146605. PainSci #52742. BACK TO TEXT
  53. Perhaps there are other methods of stretching that do work for contracture, but the average person has no idea what those are, and therapists scatter in every direction on this point, failing to agree on which “other method” works because there is no evidence base for it — just a whole lot of guessing. BACK TO TEXT