• Good advice for aches, pains & injuries

Quite a Stretch

Stretching science has shown that this extremely popular form of exercise has almost no measurable benefits

Paul Ingraham, updated


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. Stretching is not an important part of fitness. It’s primary goal — flexibility — does not correlate. And it’s also easily achieved with other kinds of exercise that are much more beneficial for fitness in other ways. Most stretching is simply a waste of time.

Unless you just enjoy it, of course. I stretch almost every day — hamstrings, lumbar erector spinae, and especially the deep gluteals are my favourites. I do it because it feels nice, 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.

I am hardly the only person to notice that stretching may not be all it’s cracked up to be, and there’s plenty of science on this.1 This article is a detailed but readable review of the key arguments and some of the most interesting evidence. Warning: you may not “just enjoy” stretching quite so much once you realize how many myths there are about its benefits.

Flexibility has been researched for over 100 years. Its track record is unimpressive, particularly when viewed in light of other components of physical fitness. Flexibility lacks predictive and concurrent validity value with meaningful health and performance outcomes. Consequently, it should be retired as a major component of fitness.

~ Nuzzo, 2020, Sports Medicine

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)

The unstretchables: some muscles are biomechanically impossible to stretch

To begin: anatomy has limits. An owl can rotate its head as much as 270° and you can’t! Owl spines and people spines are different. Although anatomy is amazingly variable (for some interesting examples, see You Might Just Be Weird) it still works about the same for most people, and there are anatomical limits on all stretches. Some more than others.

Much less tensile force can be applied to some muscles than others. Most of us will hit the end of the natural range of motion of the joint long before we’ve stretched anywhere near as hard as you can stretch other muscles. In other words, some muscles are just biomechanically awkward to stretch. I call them “the unstretchables” — a bit of hyperbole, but true in spirit. Although these muscles can be elongated, they can’t be elongated enough to create the satisfying sensation of good stretch.

There are several important muscles and muscle groups that are mechanically impossible to stretch much, including ones (like the quadriceps) that people think they are stretching.2 Even if stretching actually had the benefits that people believe in — which it clearly does not — those benefits would still not actually be available for large areas of our bodies.

This biomechanical reality is spread over the whole topic of stretching like a large, wet blanket. Whatever stretching can do for us, if anything, it has do it within the significant constraints of our anatomy, like a suntan lotion that we can’t apply to our own back. As you read, bear this broad limitation in mind. For more detail, see: The Unstretchables: Eleven muscles you can’t actually stretch hard (but wish you could)


Types of stretching (not just static)

This article is not just about the inadequacies of simple “static” stretching. Many stretching advocates are happy to join me in criticizing simple, old-school static stretching — that is, elongating a muscle and then holding still for a while. They are happy to do that because most of them decided long ago that some other method of stretching actually does work, and that’s where their allegiance lies. They feel no need to defend static stretching.

Unfortunately, there is no clear evidence that any method of stretching 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.3 It doesn’t increase flexibility any more than static stretching.4 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 is a major blow to the central xclaim of CR-PNF stretching.

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

Some supposedly advanced stretching methods 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 larger range of motion than usual (i.e. swinging your arms in a circle or walking lunges). Should we call that “stretching”? Perhaps. But I say no: although the kinship is clear, it already has its own name, and it’s a movement exercise, not “stretching.”

If an exercise doesn’t involve elongating muscles to the point of feeling significant tension for several seconds at least, it’s not stretching.


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?

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, and 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 post-workout muscle soreness.56 A major year 2000 clinical study of hundreds of soldiers showed no benefit and even some risks to stretching.7 Some extremely popular rehab stretches are particularly futile, IT band stretching most notably, which is like trying to stretch an inch-thick steel cable.

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 37-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:8

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 (

So why are people stretching?


Six popular reasons people stretch

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. 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:9

  1. flexibility, of course10
  2. warm up and injury prevention
  3. prevention/treatment of exercise soreness
  4. treatment of sports injuries and chronic pain

And a fifth which I only hear occasionally, but it’s still out there:

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

All of these overlapping goals for stretching have serious problems. Either they have long ago been proven to be impossible,11 or they never made sense to begin with, or both, or worse. Certainly none of them is a slam dunk. They will all be critically analyzed below.

One final reason for stretching gets mentioned surprisingly infrequently. People prefer to give more “technical” and serious-sounding reasons for their stretching, I guess.

  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


Part 2

Stretching in an athletic context

A lot of stretching happens in an athletic context: stretching to warm up and prevent injury and post-exercise soreness, stretching to facilitate rehab from injuries, and maybe increase performance. The more general assumption, usually unstated, is that stretching is a major component of fitness, on par with strength and endurance.

I’ll start with these goals and beliefs because they are the easiest to debunk.

But no matter how effective that debunking, nearly everyone will continue to assume that it’s different for “serious” athletes or athletes who seem to need more flexibility: gymnastics, dance, martial arts, circus arts, and so on. It’s likely that even there stretching is not actually anywhere near as important as we have believed, and maybe not even important at all. If all the information below is taken to heart, it should be clear that a “serious” athlete might actually want to avoid stretching. They have a lot of other training to do that is definitely more important — and which will also achieve flexibility.

Until fairly recently, there were few major examples of elite athletes rejecting stretching, but that's changing. The best recent example I know of is that the Australian Ballet has purged stretching; instead, it’s all about training for strength throughout the full joint range. The Australian Ballet has written about their experience with this: same or better performance, fewer injuries. Wow.

Dogma is powerful. When there’s a long tradition of doing things a certain way, it can be extremely difficult for people to accept that it might not be necessary. For years, I have regularly gotten angry email from martial artists, always sneering smugly about how I obviously know nothing because, clearly, elite martial artists know that they have to stretch. Maybe. I doubt it, and I can see which way the wind is blowing on this, but I honestly don’t know.

I do know the power of dogma. I know how many times in sports history traditional practices have been overturned and replaced by updated beliefs that were required to break new records.

And in fact I do have some personal experience with martial arts, and I know that not every martial artist is flexible or thinks they need to be. My most memorable example was a grizzled old practitioner of Aikido — the most formidable martial artist I ever met, and also the least flexible. He seemed flexible, but it was all in how he used the rather stunted range of motion he had. He worked within his limitations like an artist — a martial artist — and you would never even haved guessed he was so stiff unless you spent time with him in training.12 We never stretched much in that dojo, and an MMA club — with some very competitive members — also never did any stretching.

As the years tick by, I predict that there will be more and more stories about elite athletes who no longer stretch — but still kick ass.

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 Magazine13

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)

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, an inevitable side effect of all the activity that actually makes warm up effective for injury prevention.

Nothing about static stretching is more clear than this failure. 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.14

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.”15 And there’s more like that.16

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.1718

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 it does not prevent exercise soreness

Another extremely popular idea about stretching is that it prevents a specific type of soreness: the deep soreness that follows a hard workout. That phenomenon is called “delayed-onset muscle soreness” (DOMS) or sometimes just “post-exercise soreness.” 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.19

Recently (2016), decades after this faith first got entrenched, science finally coughed up a specific reason why it might be based on something: evidence that stretching reduces inflammation in connective tissue.20 (Exercise in general is anti-inflammatory,21 and maybe this is partly why.) Surely this is 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.22 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 DOMS232425 — and certainly not stretching.26 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.”27 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.28 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.”29 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 stretching30 — even though the authors were obviously a bit too optimistic about everything else!31 “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 candidate32 — but probably quite specific and missed by many basic, general pre-event stretching regimens.33 For injury prevention, I can think of Sports Injury Prevention Tips that are probably more effective/efficient than stretching.


Stretching research shows that stretch does not treat injury

That which prevents injury often treats it as well, and vice versa, and that’s the basic rationale for stretching as a treatment for injury. People believe that stretching prevents injury, so they believe that it can treat it as well — in a better-late-than-never way. Unfortunately, we already know that stretching doesn’t prevent injury, so it’s unlikely that it can treat it either.

But there are some more elaborate rationalizations for stretching as a treatment, chiefly that it corrects something.

Exercise is the closest thing there is to a general miracle drug,3435 and strength training is one of the best types of exercise, practically like magic: healthier and more efficient than most people realize.36 It’s also widely accepted as a major part of injury rehab, and stretching goes along for that ride. Although it’s not taken anywhere near as seriously as strengthening, millions of athletes, trainers, coaches, and healthcare professionals still consider it to be a staple of rehab.

Tedious and specific “corrective” or “therapeutic” exercises are a tired cliché of rehab and physical therapy, both strengthening and stretching. It’s what everyone (athletes and non-athletes alike) imagines their training montage will look like if they are ever hurt.

Unfortunately, corrective exercise isn’t a great reason to build strength, and its an even poorer justification for stretching. This style of rehab is largely based on the flawed and even harmful assumption that there is something in-correct about injured patients — fragile, weak, uneven — which must be fixed by sufficiently expert and precise exercise prescription.

For instance, there is often an alleged “imbalance” that consists of both overstretched and weak muscles that need to be toughened and tightened up, and tight and overworked muscles that need to be loosened and stretched.37 It’s surprising how much that single idea has boosted the perceived importance of stretching in the rehab equation.

This kind of thinking has been called the “trap” of corrective exercise, for pros and patients.38 (You can read much more about “the trap” in my main strength training article.)

Most of rehab is (or should be) just “load management” — that is, doing not too much or too little at each phase of recovery, taking baby steps back to normal function. This is doubly true for the overuse injuries, which account for a huge percentage of all athletic injuries.

Stretching obviously doesn’t have much to contribute to load management. At best, it could be considered a form of light exercise that could be used for some stimulation in the early stages… but you could and probably should mostly just stick to dynamic joint mobility drills and very easy strength training instead.

If there’s any other justification for stretching in rehab, it has to live in the much smaller neighbourhood of rehab that isn’t all about load management.

Protecting or restoring range of motion after injury

This is the most reasonable reason to stretch for rehab: not because it helps the injury itself to heal, but to prevent any related loss of range of motion, or to restore it. As explained in detail later, there is no doubt that stretching can improve range of motion. But more ROM does not have clear value in general. Many factors restrict its importance even further in a rehab context.

Stiffness is the sensation that inspires stretching in rehab, but injury stiffness — the stiffness that typically afflicts the joints near an injury — usually has nothing to do with “tight” muscles and tendons. It’s mainly just a neurologically imposed inhibition of movement, a kind of pain, a warning about movement rather than a lack of it. To the extent that it actually does involve any shortening of muscle, it’s probably either minor and temporary and things will get back to normal on their own… or it’s more serious and cannot actually be affected by stretching in any case.39

I think there are some clinical scenarios where a little stretching to maintain or restore post-traumatic ROM is probably worthwhile, but they are minor and rare.

Specific stretching for specific injuries

If not to maintain and restore range of motion, why else would you stretch an injury? What else could stretching do for an injury? Most people imagine that it’s about restoring balance: fixing things that are “too tight” and holding back recovery in some way, probably by constantly irritating the injury. In many cases, this hypothetical restriction is considered the root cause of the injury in the first place, which must be addressed to allow healing to proceed.

Stretching itself is not generally rehabilitative, because a limited range of motion does not usually cause or sustain injuries. Every kind of injury has to be considered separately, because there are all kinds of specific ideas about why one should stretch to fix different injuries. But if you go through a list of injuries and their presumed mechanisms, not many of them cannot clearly be blamed on anything that stretching can fix. Maybe none.

For instance, people believe that the reason they get iliotibial band syndrome, one of the two common kinds of runners’ knee is because the iliotibial band is “too tight.” Unfortunately, that almost certainly isn’t the problem, and the IT band is much too tough a structure to stretch in any case.40

A calf-stretching gadget, one of many on the market that are sold with claims that they can treat plantar fasciitis. Science isn’t so sure.

But the arguments for and against stretching for ITBS are completely different than they are for, say, muscle strains or low back pain. Different kinds of injuries, different arguments about stretching. My plantar fasciitis book goes on for three chapters about the possible role of stretching in treating that condition, but the bottom line is that it either doesn’t work, or not all that well.41

Over time, I will expand on a few other major examples. For now, suffice it to say that there isn’t a single clear example of specific stretching’s superiority to any other approach to rehab. Not a single one. Prove me wrong! I welcome counter-examples, with citations. Good luck finding those.

There are a handful that might be in the “promising” category, where it’s probably worth giving it a try. It’s not like stretching is expensive or risky. But even in those cases, it’s always arguable that dynamic joint mobility drills and strengthening would be better choices. For instance, in the case of muscle strain (tear), stretching may help cue the healing mechanisms in your muscle to lay down new connective tissue in a tidy way, and there’s even evidence to support that42 … but so will gentle contractions. Simply using the muscle almost certainly does the same thing, or does it better.

You can go back and forth like this with almost any injury, but the bottom line is that stretching has never been found to make a significant difference in anyone’s rehab.


In fact, stretching can actually cause injuries

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

Ironically, stretching can actually cause some of the injuries it is thought to prevent or treat. 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.43 Ehlers–Danlos syndrome (EDS) is a closely related group with known genetic causes44 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.45

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.

Here’s the story of my own ill-fated attempt to treat some neck pain with stretching:


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 runners, and with athletes who play sprinty 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.46

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.47 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.48 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.49 However, the complexities only emphasize the absurdity of the legions of people who have an oversimplified faith that stretching is important. The evidence is clear that stretching is generally pointless for enhancing performance, and possibly worse. Scientific reviews keep reporting the same conclusion.50 Maybe eventually this news will reach amateur athletes? But don’t hold your breath.

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

Stretching for pain (and for pleasure)

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 pain,5152 but it’s also a complicated, incomplete, underwhelming mess, and there are also popular stretching practices that are clearly a waste of time. One of the best examples is the idea that tight hamstrings cause back pain, and therefore stretching them is good back pain therapy. But they really don’t, and it’s really not.53 And yet that belief probably accounts for at least 50% of all the stretching people do for back pain!

In general, stretching doesn’t seem to come close to “curing” anyone, but darned if it doesn’t also sometimes seem “take the edge off” enough to make it worth trying. So people in pain stretch, and sometimes they feel better. A little bit. For a while.

People who feel stiff and tight usually 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 stiffness, but some milder dystonias probably do blend right in with other common aches and pains.

There are many possible causes of soreness and stiffness that stretching has little to do with: central sensitization, and positional cervical cord compression and multiple level radiculopathy, vitamin D and magnesium deficiency, and non-obvious entrapment of nerves (neuropathy) and bloods vessels (claudication). Several hard-to-diagnose diseases can involve long-term excessive aches and pains as a major symptom, such as the hypermobility disorders, facioscapulohumeral muscular dystrophy (FSHD), and multiple sclerosis. And then there’s drug side effects, too!54

That is just a sampling; all of these and more are summarized in 34 Surprising Causes of Pain. If you have pain from any of these sources, stretching is quite unlikely to help. In some cases, it might be useful for symptom control, at best.

Of course, there could be reasons why stretching is good for pain that we don’t understand, or are only just barely starting to understand. In the next sections, I’ll get into some of the causes of stiffness that stretching might be more relevant to: inflammation, trigger points, and contracture. But — spoiler alert — there’s literally not one clear promising example of stretching as effective medicine for anything painful. Not one.

Stretching, inflammation, and aging

Why do we so clearly get stiffer as we age? Even in people who have nothing in particular wrong with them, none of the many causes of aches and pains discussed above?

If there’s one thing most responsible for the feeling of needing to stretch, it’s probably the most common cause of aches and pains: “inflammaging.” Chronic low-grade inflammation that gradually escalates over the years, for all kinds of poorly understood reasons.55 This kind of stiffness is basically a form of mild pain that limits range of motion basically by making it uncomfortable. Our brains are more reluctant to allow free, quick movement of sore tissues. Stiffness is probably mainly a form of inhibition, then.

Unfortunately, systemic inflammation cannot be diagnosed or treated reliably by any means: it is simply too complicated and mysterious. Nevertheless, it is a trendy bogeyman, and allegedly anti-inflammatory diets in particular are extremely popular. But the best defense is simply to be as fit and healthy as possible.

And stretching? That seems like a long shot. But it’s worth discussing, at least.

Stretch your inflammation away?

A 2016 study produced one scrap of evidence that stretching reduces inflammation in connective tissues.56 It’s not clear how much “inflammation in connective tissue” is related to inflammaging — maybe none, maybe lots — but obviously there could be a connection.

We do also have some relevant evidence that inflamed connective tissue is associated with back pain,57 which is of course the epicentre of stiffness as we age (although back pain actually backs off quite a bit on the far side of middle-age).

That evidence is all there is, and it’s too scanty to trust yet. In fact, I am confident that these isolated research clues are probably misleading, and I don’t really buy that stretching reduces inflammation any more than I believe that massage reduces inflammation (a popular idea based on one over-hyped study58). But let’s keep our minds open.

If stretching does help some inflammation resolve, obviously that would be good for us. 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 stiffness and soreness.

Chances are strong that inflammaging is a steamroller that stretching cannot really touch, however. There are several high plausible mechanisms for inflammaging that are quite unlikely to be affected by stretching. The best hope is that stretching is somehow mildly anti-inflammatory, regardless of what caused the inflammation, but it’s more likely that fitness is much more “anti-inflammatory” than stretching specifically. Practically any functional stimulation of the same tissue — not just stretching — might have the same modest anti-inflammatory effect.


Stretching for trigger points

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

The story goes like this: trigger points are isolated regions of contracted muscle fibres, basically micro cramps. If that’s how they actually work, then stretching might be a viable treatment method. Unfortunately, how they work is highly debatable, and basically unknown.

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 cannot 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 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.

This topic is covered in much greater detail (about 10x the length of this section) in my trigger points book.


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.


Stretching does feel good, and maybe that is a kind of pain-killer

If stretching is mostly irrelevant to pain and injury, 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? Why is this true for so many of us?

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, and I suspect it’s about as medically useful as a back scratch.

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.


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:

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.


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 must be an effective prevention/treatment for contracture, perhaps the only viable option. 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.59 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!

Treatments are usually more obviously valuable to those who need them more. For example, the effect of acetaminophen is more obvious to someone with a headache. This very basic principle doesn’t always apply, but it usually does. This evidence shows that stretch does not meaningfully help even for a condition where the need for tissue elongation is dramatic.

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.60

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


Part 4

Stretching for flexibility

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.

~ Flexibility, by William Sands, p. 389

There is really only one effect of stretching that seems to be clear and (almost) uncontroversial: it does actually increase flexibility. Even just plain old static stretching.

For whatever it’s worth, people do seem to be more flexible when they stretch regularly for a while. Meaningful improvement is elusive, but it can be done. The phenomenon is widely observed, and seems to have been confirmed by experiments. I previously cited Marshall et al — a decent, recent example — and there are more (cited and discussed below). Less than you’d think at this point in history, though! There’s hundreds of studies of anything these days, but not this.

So, you can get more flexible “for whatever it’s worth,” but what is it worth?

Is it actually even a benefit?

The American College of Sports Medicine believes that flexibility is “important in athletic performance (e.g., ballet, gymnastics) and in the ability to carry out activities of daily living.” It’s a "major component" of fitness, along with body composition, cardiovascular endurance, muscle endurance, and muscle strength. They recommend 2–3 days of stretching per week (2–4 repetitions of multiple stretches per day).61

Personal trainers certainly buy into it. About 80% of American trainers prescribe static stretching — for all the reasons, but mainly for the flexibility.62

I will start by arguing that is not worth much to most people, even athletes. To make that case more effectively, it’s also important to consider the nature of flexibility. When someone increases their flexibility, what changes, exactly? How does it work? Contrary to what nearly everyone believes, it’s probably not by actually making tissue “longer.” I’ll close the flexibility discussion by looking at plasticity versus neurological tolerance.

The value of 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 craving for greater range of motion. We love the idea. 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.

What exactly are you planning to do with your flexibility?

Even abnormally poor flexibility is usually no big deal, as long as you are otherwise healthy. There just aren’t many functional limitations caused by being super stiff that actually matter much. A couple examples:

  1. Toe touching is the ultimate in trivial flexibility goals. People can live their whole lives without being able to touch their toes without any practical consequences, for instance. This is one of the key points of the article: that flexibility should only matter if it can help us do something that actually matters to us. For the martial artist, flexibility enables performance goals that martial artists care about! Great! But if a dude doesn’t care if he can touch his toes ... so what?
  2. Reaching bra buckles actually matters to women, of course, but — unless something is diagnosably wrong with that shoulder — few women are so inflexible that it’s an issue. If it was, they would certainly consider it well worth fixing -- et voila, a job for stretching! But it's both rare and easy to fix: it wouldn’t take much improvement in shoulder ROM.

For stretching with a flexibility goal to matter, we have to identify a common and meaningful functional limitation that can be overcome by increasing range of motion. There are lots of examples thatare rare and trivial ... or common and trivial ... or rare and meaningful ... but not both common and meaningful. And so the seemingly worthy goal of better ROM is actually quite marginalized — it doesn't and shouldn't matter to most people, most of the time.

If inflexibility is good enough for Eliud Kipchoge, it’s good enough for you. As of 2018, Mr. Kipchoge is the world’s fastest marathoner.63 But the man cannot touch his toes! This is an anecdote from someone who trained with him leading up to when he broke that record:

He was extremely inflexible. After an easy morning run (16km in 1hr10mins), I stretched with the group. Most of them were fairly flexible in the hamstrings (ie. standing straight legged and bending over to touch your toes with your knees straight and being able to touch your toes. Eliud was miles off). He was nowhere near touching his toes! They all found it hilarious that he couldn’t come close to touching his toes.

Matt Fox for, “Training with Eliud Kipchoge – 5 Things That Surprised Me

Flexibility and general health

When people have good aerobic capacity — when they are fit enough to efficiently distribute oxygen to all their cells — they are measurably more functional and healthier in all kinds of other ways too. If stretching is also an important part of fitness, then it too should be linked to all kinds of other good stuff.

It’s not. Stretching barely registers on any measure of health and function. More flexible people do not die less or fall down less as they age. They don’t have clearly higher quality of life (a tough one to measure, but it’s been done). They don’t have less back pain or injuries, and in fact they may have more. They don’t have lower blood pressure, resting heart rate, cholesterol — those markers of fitness are much more strongly predicted by weight and endurance.64

Flexibility also isn’t linked to the other components of fitness: flexible people are cannot lift more, run farther, or slip through narrower cracks. James Nuzzo: “Absence of correlations between flexibility and other fitness components indicates flexibility is a distinct trait, but not one particularly important for health and function.”

But what if you had to increase flexibility? If it mattered? Could you do it?

Yes! Congratulations!

Stretching can increase flexibility. Many studies over many years have shown this in many ways,6566676869 and I’ll explore some that evidence for tips and tricks. 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. How much of an effort? That’s the next topic.


Stretching dosage for flexibility: intensity, frequency, and duration

Hold it right there! For how long exactly, though? And how often? How hard? What works best? Is 5 seconds of light stretch every other day for a couple weeks enough? Probably not. Or should it be 5 minutes of brutally intense yanking on your muscles three times a day for three months? That’s probably too much — even if it was definitely more effective, ain’t nobody got time for that. The bottom line:

In practice, most people stretch only a small selection of tissues quite briefly, seconds only, and erratically. Only the most diligent of us can actually sustain a daily habit for long. We don’t know if that’s enough to achieve the goal. The evidence suggests that holding a stretch for 15 seconds is better than 5… but only a little bit.70

In 2011, a nicely done experiment by Marshall et al showed that regular hamstring stretching substantially increased range of motion in normal university kids.71 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 from a sane stretching dosage. For whatever it’s worth.

Battle of the experts

Here is a vivid example of how poorly understood this all is. This is an excerpt from one of my school text books, a weighty and authoritative tome, a bible of therapeutic exercise (granted, out of date now, but this is the text I learned from):

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. Again, ain’t nobody got time for that.

The idea of a “correct” dosage (or any aspect of technique) is mostly a fantasy. And yet, somewhere between “not nearly enough” and “way too much” there is probably a sweet spot.

Getting hard core: more extreme efforts undoubtedly do 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.

Even these unusual athletes are not chasing flexibility alone, and most athletes have much higher priority training goals. “Athletes usually don’t require extreme ranges of motion,” writes Todd Hargrove,72 “but rather extreme control at the end of relatively normal ranges of motion.”

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.


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.73 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.74 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.75

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.767778 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.79 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 one80 — 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.


Part 5

So … is stretching good for anything?

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

How about this? It’s good for your heart!81 “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.

“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


“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.82 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.


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:

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


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About Paul Ingraham

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

I am a science writer, former massage therapist, and I was the assistant editor at for several years. I have had my share of injuries and pain challenges as a runner and ultimate player. My wife and I live in downtown Vancouver, Canada. See my full bio and qualifications, or my blog, Writerly. You might run into me on Facebook or Twitter.

Part 6


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. Updates shown here are the most recent only; an archive of all updates is coming soon (Jun 2020).

April — More content: Added some examples of stretching being rejected by elite athletes. [Updated section: Stretching in an athletic context.]

February — More information: Added detail about the practical importance of flexibility. Or lack thereof. Weirdly, this update was harvested from a decade-old Facebook comment. [Updated section: The value of flexibility.]

January — Science update: Added an important example, stretching the hamstrings for back pain, with a few relevant references. [Updated section: Stretching for pain (and for pleasure).]

January — New section: No notes. Just a new chapter. [Updated section: Stretching research shows that stretch does not treat injury.]

2019 — New section: Some new content, and some old content transplanted from other sections. There’s certainly more to do on dosage, but I think it’s a solid summary so far. [Updated section: Stretching dosage for flexibility: intensity, frequency, and duration.]

2019 — New section: No notes. Just a new chapter. [Updated section: Stretching, inflammation, and aging.]

Archived updates — 13 additional older updates are listed on another page. ❐



  1. Nuzzo JL. The Case for Retiring Flexibility as a Major Component of Physical Fitness. Sports Med. 2020 May;50(5):853–870. PubMed #31845202 ❐

    This is the first of many citations in this article, but it’s also one of the best and most general, and highly recommended reading for professionals. It is like a more scholarly and formal version of this article.

  2. Other major examples include: masseter and temporalis, the suboccipitals, the thoracic paraspinals, latissimus dorsi, the gluteals, the foot arch muscles, and the IT band (of IT band syndrome fame). Some of these muscles can, sort of, be stretched. But all of them are limited to a moderate intensity stretch at best (e.g., the gluteals), in most people, most of the time, using reasonably accessible methods.
  3. 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.
  4. 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 ❐
  5. 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.

  6. 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 ❐
  7. 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.”

  8. 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!
  9. 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.
  10. 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.
  11. 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.
  12. His wrist ROM was especially memorable: it was like his hands were welded onto the end of his forearms. He once showed me how far he could bend his wrist back, which was not at all. Aikido uses a lot of wrist locks, so his sturdy and inflexible wrists made him almost impervious to those … but with no detectable functional deficit either.
  13. Cooper, Bob. “The Rules Revisited.” Runner’s World. September, 2009. p. 59.
  14. 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.
  15. 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.
  16. 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!

  17. 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.
  18. 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!

  19. 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.

  20. 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.

  21. Peterson AM, Pedersen BK. The anti-inflammatory effect of exercise. J Appl Physiol. 2005 Apr;98(4). PainSci #52512 ❐
  22. 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.
  23. 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.”

  24. 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.”

  25. 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 ❐

    Forty women were subjected to intense training of the biceps and brachilias muscles, until they were sore, and then treated with one of four treatments for DOMS: massage, TENS (electrical stimulation), and ergometry (basically light exercise, to stimulate metabolic activity), and rest. Treatment were given immediately after and then 24 and 48 hours after. There was no difference in the results for any of the women.

  26. 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.

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


    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.

  28. 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 ❐
  29. 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. 2011 Jun 15. PainSci #55243 ❐
  30. 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 ❐
  31. They thought strengthening looked good, but based their very positive-sounding conclusions on only four studies of dubious quality and relevance.
  32. 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. 😜

  33. 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.
  34. Academy of Medical Royal Colleges. Exercise: The miracle cure and the role of the doctor in promoting it. 2015 Feb. PainSci #53672 ❐

    This is the primary authoritative source of the quote “exercise is the closest thing there is to a miracle cure.”

  35. Gopinath B, Kifley A, Flood VM, Mitchell P. Physical Activity as a Determinant of Successful Aging over Ten Years. Sci Rep. 2018 Jul;8(1):10522. PubMed #30002462 ❐ PainSci #53004 ❐

    If you want to age well, move around a lot!

    We already know that physical activity reduces the risk of several of the major chronic diseases and increases lifespan. “Successful aging” is a broader concept, harder to measure, which encompasses not only a reduced risk of disease but also the absence of “depressive symptoms, disability, cognitive impairment, respiratory symptoms and systemic conditions.” (No doubt disability from pain is part of that equation.)

    In this study of 1584 older Australians, 249 “aged successfully” over ten years. The most active Aussies, “well above the current recommended level,” were twice as likely to be in that group. Imagine how much better they’ll do over 20 years …

  36. Research shows strength training is much more efficient form of exercise than most people realize, and almost any amount of it is much better than nothing. You can gain strength and all its health benefits fairly easily. For more information, see Strength Training Frequency: Less is more than enough: go to the gym less frequently but still gain strength fast enough for anyone but a bodybuilder.
  37. The “Upper-Crossed Syndrome” (UCS) sounds impressively technical. It is the apex of clinical storytelling about posture in therapy culture, and the prototypical “muscle imbalance” theory, and yet it basically just means slouching: head and shoulders forward, mostly, with several complicated assumptions about its causes and consequences. With UCS, your muscles are presumed to be like dysfunctional ship’s rigging: some are weak and loose (“inhibited”), while others are too strong and tight (“facilitated”). Viewed from the side, you can draw diagonal lines between these groups that cross. (There’s a Lower-Crossed Syndrome as well.) Dr. Janda was a pioneer and did good work with the information he had at the time, but he was probably mostly wrong about UCS; muscle imbalance theories like UCS have not done well over the last couple decades. For more information, see the upper-crossed syndrome section of my posture article.
  38. Tumminello N, Silvernail J, Cormack B. The Corrective Exercise Trap. Personal Training Quarterly. 2017 Mar;4(1). PainSci #52905 ❐

    The authors decisively but gently tip over the most sacred cow of personal training and therapy: corrective exercise, which is grounded in the assumption that there is something in-correct about patients — fragile, weak, or uneven — which must be fixed by sufficiently expert and precise exercise prescription. Exaggerating the importance of defect-correction is actually dangerous for the patient (nocebic): “When clients are told such things about themselves from an authority figure (as they might be during some corrective exercise evaluations), that this potentially makes one’s clients less resilient and more prone to injury and pain.” Translation sans diplomacy: *stop #%&^ telling patients they are fragile and weak!*

    The corrective exercise trap is also about overconfidence in the value of allegedly advanced rehab exercise, when the evidence is overwhelming that corrective exercise is no better than general exercise. “The danger here” — the trap! — “is that many fitness professionals might end up making their training process more about a formalized evaluation procedure and less about good personal training.”

    (See more detailed commentary on this paper.)

  39. If an injury causes more stubborn loss of ROM by the mechanism of contracture or derangement of the bone or cartilage in a joint, stretching is going to be futile.
  40. Ingraham. IT Band Stretching Does Not Work: Stretching the iliotibial band is a popular idea, but it’s very hard to do it right, and it’s probably not worth it.  ❐ 2631 words.
  41. Radford JA, Landorf KB, Buchbinder R, Cook C. Effectiveness of calf muscle stretching for the short-term treatment of plantar heel pain: a randomised trial. BMC Musculoskelet Disord. 2007 Apr;8:36. PubMed #17442119 ❐ PainSci #52975 ❐

    This trial of stretching for plantar fasciitis made an effort to blind the participants. That is, the 92 study subjects didn’t know what treatment was being tested, reducing the likelihood of bias in reporting on the results. This was achieved by adding sham ultrasound to both the treatment and control groups, a good strategy. After two weeks, unfortunately there was no difference between the groups: “a two-week stretching program provides no statistically significant benefit in ‘first-step’ pain, foot pain, foot function or general foot health compared to not stretching.”

    It could have been a larger, longer study, sure, but 92 feet is quite a decent sample size for studies of this kind of thing. And although stretching benefits might ramp up over time, that’s probably wishful thinking, and you’d certainly hope to see clearer signs of progress after two weeks of diligent stretching.

  42. Malliaropoulos N, Papalexandris S, Papalada A, Papacostas E. The role of stretching in rehabilitation of hamstring injuries: 80 athletes follow-up. Med Sci Sports Exerc. 2004 May;36(5):756–9. PubMed #15126706 ❐

    About 40 Greek athletes who stretched more intensively recovered faster than those who stretched more lackadaisically (and the effect is probably not limited to the Hellenic people). How much faster did they recover? They regained their range of motion about 22% sooner (5.6 days instead of 7.3), and their “rehabilitation period” was about 12% shorter (13.3 days instead of 15 days). The researchers reported that this was of “great importance in treating muscle strain injuries.” I’m not quite so thrilled by those numbers: getting back in the game about 36-hours sooner is not nothing, but I wouldn’t call it greatly important. One could easily argue that a wee improvement in healing time isn’t worth the risk of injury, or even the tedious routine of stretching. One could also argue that they really should have compared stretching to other kinds of rehabilitative exercise, and the difference probably would have disappeared.

  43. 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.
  44. “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).
  45. 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.”
  46. 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.
  47. 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.”
  48. 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.
  49. 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.
  50. Baxter C, Mc Naughton LR, Sparks A, Norton L, Bentley D. Impact of stretching on the performance and injury risk of long-distance runners. Res Sports Med. 2017;25(1):78–90. PubMed #27912252 ❐
  51. 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.

  52. 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 and 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!

  53. This is a complex topic I cover in detail in my back pain book. Short version: even simple hamstring stretching definitely makes hamstrings more extensible and improves ROM (Marshall et al), but there’s no correlation between back pain and how the hamstrings are behaving in the first place. A 2019 scientific review (Hori et al) was inconclusive “due to very low quality of evidence.” A 2017 review (Sadler et al) was a little more reckless, and went with a conclusion based on just a handful of studies, including some that had been deliberately ignored by the more recent review, and they reported a 4% greater chance of back pain in people with inflexible hammies, with is either trivial or just untrue because it’s based on such weak data. For an example of a simple negative trial, see Marshall et al: they reported “no [hamstring] relationship to actual disability.”
  54. 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 with an extraordinary range of nasty side effects, most notoriously tendinitis), the retinoids (for skin conditions, like Accutane for acne), and Trintellix (an antidepressant). Withdrawal from benzodiazapenes (Valium, Ativan, Xanax, etc) can be extremely uncomfortable and painful; unaware of the risks, many people stop taking them carelessly and suffer quite a bit without ever knowing why. For more detail on some of these, see 34 Surprising Causes of Pain.
  55. How do we get into this mess? Inflammaging correlates with poor fitness and obesity (metabolic syndrome, the biological precursor to diabetes and heart disease). And that, in turn is linked to chronic psychological stress (and of course biological stresses too, like smoking and sleep deprivation). And then there are several other unproven but plausible reasons why inflammation escalates as we age, such as the accumulation of permanent minor infections, lasting collateral damage from past infections (essentially autoimmune disease and allergies that are too subtle or nonspecific to diagnose), and environmental poisons.

    For a much more thorough exploration of these possibilities, see Chronic, Subtle, Systemic Inflammation: One possible sneaky cause of puzzling chronic pain.
  56. Berrueta 2016, op. cit.
  57. 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 patients: see Langevin for more commentary on the implications of both studies.

  58. Ingraham. Massage Does Not Reduce Inflammation: The making of a new massage myth from a high-tech study of muscle samples after intense exercise.  ❐ 4166 words.
  59. 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 ❐
  60. 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.
  61. American College of Sports Medicine. ACSM’s guidelines for exercise testing and prescription. 10th ed. Philadelphia: Wolters Kluwer; 2018.
  62. Waryasz GR, Daniels AH, Gil JA, Suric V, Eberson CP. Personal Trainer Demographics, Current Practice Trends and Common Trainee Injuries. Orthop Rev (Pavia). 2016 Sep;8(3):6600. PubMed #27761219 ❐ PainSci #52598 ❐
  63. 2:01:39, which is 1:18 faster than the previous record, the greatest improvement since 1967. This dude is fast.
  64. That’s a lot of claims. Rather than citing to support all of them, I’ll just refer you to Nuzzo’s very detailed review, previously cited, which cites many examples and also acknowlgedes some exceptions. The exceptions, however, mostly just “prove the rule.”
  65. Freitas SR, Mendes B, Le Sant G, et al. Can chronic stretching change the muscle-tendon mechanical properties? A review. Scand J Med Sci Sports. 2018 Mar;28(3):794–806. PubMed #28801950 ❐ “Stretching interventions with 3- to 8-week duration do not seem to change either the muscle or the tendon properties, although it increases the extensibility and tolerance to a greater tensile force.”
  66. 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 ❐ “All forms of training induced ROM improvements, typically lasting <30 min.”
  67. Medeiros DM, Cini A, Sbruzzi G, Lima CS. Influence of static stretching on hamstring flexibility in healthy young adults: Systematic review and meta-analysis. Physiother Theory Pract. 2016 Aug;32(6):438–445. PubMed #27458757 ❐ “In all tests, the results favored static stretching compared to control group… In conclusion, static stretching was effective in increasing hamstring flexibility in healthy young adults.”
  68. Decoster LC, Cleland J, Altieri C, Russell P. The effects of hamstring stretching on range of motion: a systematic literature review. J Orthop Sports Phys Ther. 2005 Jun;35(6):377–87. PubMed #16001909 ❐

    Results were inconclusive as to whether or not any particular type of stretching could improve knee ROM. Overall, however, “the evidence appears to indicate that hamstring stretching increase range of motion,” regardless of the technique used. “Appears to indicate” is pretty inconclusive.

  69. Harvey L, Herbert R, Crosbie J. Does stretching induce lasting increases in joint ROM? A systematic review. Physiother Res Int. 2002;7(1):1–13. PubMed #11992980 ❐ “The results of four 'moderate' quality studies show a convincing effect of stretching in people without functionally significant contracture.”
  70. Roberts JM, Wilson K. Effect of stretching duration on active and passive range of motion in the lower extremity. Br J Sports Med. 1999 Aug;33(4):259–63. PubMed #10450481 ❐

    Another (small) study to determine if stretching for five or fifteen seconds can make a difference in range of motion of the joint. It concluded: “These findings suggest that holding stretches for 15 seconds, as opposed to five seconds, may result in greater improvements in active ROM. However, sustaining a stretch may not significantly affect the improvements gained in passive ROM.” In other words, the returns diminish quickly.

  71. 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 ❐
  72. Hargrove T. Playing With Movement: How to explore the many dimensions of physical health and performance. 1st ed. self-published; 2019. p. 148
  73. 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 ❐
  74. 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.

  75. 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).

  76. 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.

  77. 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.

  78. 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.”

  79. 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!
  80. 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.”

  81. 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.

  82. 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.