A Stretching Experiment
What happens when you stretch your hamstrings intensely for several minutes a day in a steam room?
I am a skeptic, known for my criticisms of stretching.1 However, I do enjoy stretching, and even I believe that diligent stretching can increase flexibility, because that’s the one effect of stretching that research has backed up. So for thirty days this summer I optimistically2 stretched my hamstrings — an experiment in the “lab of me.” I was truly disciplined: four full minutes of intense stretching per leg, per day. I did every stretch in a piping hot steam room, which is widely considered an ideal circumstance for stretching, whether that is true or not. What happened?
- My “warm” flexibility increased slightly. I could always increase my flexibility during a stretching session, and slightly more so near the end of the experiment.
- My “cold” flexibility never increased at all: no matter how far I was able to stretch during and immediately after a stretching session, I always quickly reverted to my original, poor flexibility.
- Symptoms of minor stiffness and pain in the hips and legs did not change.
In short, the experiment clearly shows that stretching did not work well at all for me. My gains were trivial, and they cost me about three full hours of actual stretching, plus another ten hours or so for the rituals of changing, and showering — a far greater and more consistent commitment than I had ever actually made to stretching before, and for only a single muscle group.3 The results did not justify that kind of time.
Limitations of my experiment
Obviously, with a sample size of one, this experiment in the Lab of Me cannot tell us much about you, or anyone else.
Biological responses to stretching are probably a witch’s brew of genetic, psychological, and medical factors, and even the most extraordinary and sustained effort might fail to produce results in some folks, while a trivial investment could succeed admirably with others.4 It may be quite sensitive to age, for instance: I might have gotten completely different results in my 20s.5
So I can’t be “wrong” or “right” here. This article isn’t an indictment of stretching. It proves nothing; it can’t prove anything; it is the sound of one hand clapping. It’s just a report on what happened to me when I tried to stretch in a (very!) popular style. Make of that what you will.
In short, it’s a thought-provoking über-anecdote, and no more.
Hard core: a truly disciplined effort
Like many people, I have a poor track record with sticking to my resolutions. I even have an embarrassing habit of dabbling in some self-treatment or exercise method, and then thinking and talking about it as though I’ve given it a fair shake, when in fact I really just barely scratched the surface. (And now that I’ve confessed it, perhaps you can too? I know I’m not alone!)
If you’d asked me before this experiment how much experience I had with stretching, I probably would have said, “Lots!” And that would have been true … in some ways. But the inspiration for the project was my red-faced insight that I have never actually stretched with enough dogged consistency and uncomfortable intensity to claim to really know how it affects me. For a prominent stretching skeptic, that’s a little uncomfortable to realize. I had to put it right.
The goal here was to be disciplined enough to remove all doubt that I have really tried “hard enough” — certainly quite a bit harder than most other people will ever bother with.
Why do I want to be more flexible anyway?
I blame George Lucas. I saw Star Wars in 1977 at the age of five, and thereafter wanted (badly) to be a Jedi knight, or at least a ninja (when I was in a more realistic mood), and it is common knowledge that both Jedi and ninja are limber. My craving to be more flexible probably dates all the way back to those boyish ambitions.
I am an avid ultimate player these days, but I have yet to see any real need for flexibility in that sport,6 and I have gotten nothing but discouragement about stretching from my extensive academic study of the subject: stretching has no clear or proven benefits for most athletes, and not for lack of trying. The exceptions are exotic.7
I embarked on this experiment simply out of professional interest and the emotional hooks of being a wannabe Jedi. You never know: if I can achieve flexible hamstrings, anything might be possible. Mind powers, for instance.
Why a steam room?
Most people assume that heat — especially moist heat — is a significant stretching aid. This is probably not true,8 and I am not aware of any specific physiological reason why it would be.9 However, I can certainly attest that it is pleasant to stretch in heat.
I have an excellent spa in my building in downtown Vancouver. We have a hot tub, a sauna, a steam room, and a small swimming pool. For each stretching session, I spent a couple minutes in the hot tub while the steam room got steamy. Then I spent another couple minutes in the steam getting thoroughly hot myself before beginning the stretches. The temperature was between 40–48˚C (104–118˚F).
48˚C is hot.
Hot enough to make you think, “If I got locked in here, my goose is cooked.”
It suited my purpose to stretch in an environment that “should” work better for stretching, a theoretically ideal environment. A good result would not necessarily suggest the importance of heat. But a poor result “even stretching in a steam room” is more noteworthy. If stretching thoroughly in a hot, steamy room is not effective, what would be?
Two minutes is a long time
My stretching ritual was broken into three two-minute parts:
- Two minutes of stretching the left hamstrings.
- Two minutes of stretching the right hamstrings.
- Two minutes of stretching hamstrings and adductors on both sides (leaning forward between legs spread out to the sides).
Two minutes is a surprisingly long time! In the wild, runners and other casual athletes rarely stretch a muscle for more than 20 seconds. It would be surprising to see anyone hold a single stretch in a pre-game warmup for more than a minute. Even in yoga classes, few individual stretches go much past the minute barrier.
I chose two-minute stretches because I wanted to remove all doubt that I had stretched enough. On the other hand, if a stretching regimen isn’t practical, there’s not much point in proving that it works. Two minutes was my compromise duration.
Two minutes — times three! — is more than long enough to get bored. It is also long enough to get too hot. On many days, I could barely tolerate the heat long enough for the last stretch (raising the question of how one could possibly manage to stretch much more, if heat was indeed a required element).
Two-minutes isn’t long
While on the one hand I often found the ritual tedious and near the limits of my heat tolerance, on the other hand the stretches were surprisingly complex: sensations changed and shifted conspicuously throughout the stretch, and there is no doubt that I continued to “settle in” to each stretch right up to the end.
In this sense, my long stretches seemed almost fleeting, and sometimes felt like I was really just getting started as the timer went off.
How long would the sensation of “settling in” have continued? I did experiment with that on at least three occasions, extending a single stretch to a whopping six minutes. The sensations continued to change, and flexibility continued to slowly increase during those stretches — but the returns were diminished as I went, and I gained much less range in the second three minutes than in the first three. For instance, on one day my reach increased nearly a finger-length in the first three minutes. After another full three minutes of stretch, I was only able to add about another centimetre (details of my measurements revealed below).
While long-duration stretches may be generally impractical, they are certainly interesting, and I am keen to try them out more thoroughly.
Why the hamstrings?
The hamstrings are probably the most stretched of all muscles. If stretch is not useful here, it reflects poorly on the great majority of actual stretching. If hamstring stretches are useful, it validates the majority of human stretching.
The hamstrings are the largest easily stretched muscle group. Nowhere else in the body can you pull on anywhere near that much muscle so conveniently. The knees can easily be held straight while the weight of the torso does the rest of the job almost without effort. Only one muscle group is larger — the quadriceps — and it is nowhere near as biomechanically amenable to stretch. All other muscle groups are either quite a bit smaller, less convenient, or both.
The hamstrings are a trio of long, lanky muscles in the back of the thigh: semitendinosus, semimembranosus & biceps femoris.
The low back, hips, buttocks and hamstrings are also an extremely common place for people to have limited flexibility, sensations of stiffness, and pain — all of which I share. My hamstrings feel chronically unpleasant, and when I stretch them it feels as though I am scratching an itch from the mid-back to my calves. I wanted to see if a serious stretching habit could extend those benefits beyond the ritual, and reduce my overall load of stiffness and discomfort in this region. Soreness and stiffness probably aren’t caused by inflexibility,10 but I was certainly hopeful anyway.
If there is any stretch that can provide good therapeutic bang for your stretching buck, it’s got to be a hamstring stretch. And if it can’t, then it’s doubtful that any stretch can.
And it couldn’t. My flexibility barely changed, and my stiffness and aches and pains were unchanged in this period. Perhaps most revealingly, it never felt like there was any less “itch” — the feeling of the “need” to stretch never lessened, and every stretch felt like the first stretch.
The results: flexibility
I measured how far I could reach during each stretch. The tiled surfaces of a steam room make for convenient landmarks. I also tested my flexibility with a toe-touch: standing on the edge of a stair, locking my knees (for consistency), and observing the position of my fingertips relative to the edge of the stair. I used a standing knees-locked toe-touch stretch to check my flexibility immediately before and after stretching in the steam room, and at rough intervals afterwards, and also at a few other “interesting” points — i.e. after a long period in a chair, or after some intense exercise.
These methods were not precise, but they were certainly good enough for my needs. Any changes in flexibility that couldn’t be detected this way wouldn’t be of much interest anyway.
I looked for changes in flexibility before, during, and right after sessions, as well as at selected times later that day.
- My cold flexibility never changed. It was like I was starting from zero every day. Prior to each session, I was always just barely able to touch the edge of the step. This finding makes it clear that my effort did not make me more flexible in general.
- My flexibility during sessions increased marginally. By the end of each session I was able to reach about 15–25% further11 — perhaps slightly more in the last week of the experiment. However, at all times these modest improvements were equally and extremely temporary …
- My flexibility always rapidly returned to normal (i.e. no improvement) after stretching — within just a few minutes!12 — for the entire duration of the experiment.
- All attempts to sustain the flexibility I obtained during sessions failed.13
I also made a point of checking my flexibility after periods of activity and inactivity. I speculated that improvements in flexibility might be masked by a long period of sitting, or more evident when warmed up from a good walk. However, I was equally inflexible at all times, regardless of activity level.
The only time I ever saw an increase in my flexibility was during and immediately after stretching sessions. The magnitude of these changes was, at its greatest, no more than a finger length. That is, I was never able to reach more than about 8cm (3in) further than my baseline, and that was on a good day. Often my gains in a session were only half that. None lasted for more than a few minutes.
The results: the sensations of stretch
I also paid close attention to the sensations of stretch. Obviously this is an imprecise and subjective measurement, but it was a simple measurement: how uncomfortable was it to stretch?
My sensations during stretch were consistent: the limit of my range was always uncomfortable.
The intensity of my discomfort was always roughly proportionate to how close I was to the end of my range — where that happened to be at the time. I thought it was possible that, as I progressed through the experiment, I might find that my range was limited more by painless resistance of my tissues, but that did not happen. Although I could stretch a little farther, it was always pain that stopped me, and never just painless tightness.
Usually the discomfort was more of a “good pain,” and I was content to endure it — a pleasant stretching experience, with unpleasantness just around the corner if I had increased the intensity. Occasionally the sensations were more like “bad pain,” and it was an unpleasant struggle to sustain the same stretch as I had the day before. Whether the discomfort was “good” or “bad” seemed to correlate with my mood, but in complex ways. For instance, if I was frustrated by life and had nearly lost my temper at an inanimate object earlier that morning, I might experience the stretch as frustrating as well; or, paradoxically, it might have been just the opposite, a nice oasis from my troubles.
It was difficult to predict, but definitely connected somehow. Pain is an opinion, after all.
Mother warned me about days like this (but never mentioned stretching)
I didn’t know that bad days would make it so hard to stretch. A pattern throughout the experiment was that stretching was not only more uncomfortable on days when I hadn’t slept well — which is at least once a week for me, and several nights during one rough patch this past month — but my flexibility was also significantly less. If I had recorded my flexibility exactingly enough to make a graph out of the data, these days would certainly have shown up as a few distinct chasms, maybe circled in the red, with frownie faces.
Adding insult to injury, there were no especially good days to compensate for these stinkers. I was either making the usual barely measurable headway, or I was having a rough time of it. And the magnitude of the badness on the bad days was significantly more noticeable than any of the temporary improvements I ever achieved. So on the one hand I had numerous incidents of significant, uncomfortable reduction in flexibility for many hours at a time. On the other hand I had extremely temporary minor gains even on the best days. Why did I do this again?
The results: symptoms in the area
As mentioned above, my posterior legs, buttocks and low back have been stiff and uncomfortable for many years, with occasional flare-ups of moderate pain. The hope that some truly diligent hamstring stretching might make a difference was certainly one of the main reasons I chose this experiment. That it is difficult to spell out exactly how stretching is supposed to help is completely irrelevant: it is a common prescription, and I wanted to concern myself only with whether it would work for me and worry about the how only if it did.
It did not.
Measuring symptoms was certainly the most imprecise of my results. Although a simple score on a scale of ten is a well-established way of measuring pain, I didn’t think it would be meaningful in this case, because I have no serious pain and I would mostly be trying to discriminate between quite subtle differences at the bottom of the scale. So I kept it super low resolution, almost binary, and just asked myself: do I have symptoms or not?
The result may have been imprecise and subjective, but it is certainly accurate: I continued to have symptoms of minor aching and stiffness in the region throughout the entire experiment. There was no noticeable improvement at all, not even a subtle one.
Achieving flexibility might be possible, but it’s definitely not practical
It is theoretically possible that more stretching would have done the trick. If I now try stretching for twelve minutes per leg per day for three months with even greater intensity, I might yet increase my flexibility. And I may yet do that experiment as well. But I will never stretch that much for anything other than experimental interest. Cirque du Soleil will have to put me on their payroll before I ever make a habit of stretching that much.
In my first experiment, my goal was not to find out if it is possible for me to increase my hamstring flexibility, but to determine if it’s practical to do so. The limits of my discipline were also the limits of my patience — the most amount of effort I would be willing to tolerate for some modest results. If it takes more than this to get flexible, it clearly takes too much. Even if my flexibility increases had been somewhat larger and more lasting, the bang for buck would have been poor.
A therapeutic exercise must deliver unambiguous value to compete with all the other goals I need to make time for. My time is not a toy to be pissed inefficiently away on dubious goals. I only get this one life, and I intend to make good use of it. I am done with stretching, with the exception of some possible future experiments, and occasional brief stretching for pleasure. And that won’t be a big loss — since I don’t particularly need more flexible hamstrings anyway.
About Paul Ingraham
I am a science writer in Vancouver, Canada. I was a Registered Massage Therapist for a decade and the assistant editor of ScienceBasedMedicine.org for several years. I’ve had many injuries as a runner and ultimate player, and I’ve been a chronic pain patient myself since 2015. Full bio. See you on Facebook or Twitter., or subscribe:
If you found this article useful, you may also be interested in some other articles I’ve published:
- Quite a Stretch — Stretching science has shown that this extremely popular form of exercise has almost no measurable benefits
- Stretching Injury — How I almost ripped my own head off! A cautionary tale about the risks of injury while stretching
- The Unstretchables — Eleven muscles you can’t actually stretch hard (but wish you could)
What’s new in this article?
2011 — Added audio edition of the article.
2011 — Numerous edits and minor additions based on initial wave of public responses to the article.
2011 — Publication.
- The main stretching article on this website, Quite a Stretch, is quite popular, quite widely cited, and quite critical of most common stretching beliefs and practices.
- My mood about it is important. I did not expect to fail. On the contrary, I expected to succeed. I am “biased” against stretching in general, but biased in its favour on this point. I went into this believing that I would probably get good results, because that is what the evidence supports.
- Even supposing the results had been more satisfactory, the time required to extend them to other areas of my body would have been logistically challenging! The same commitment to five stretchable muscle groups (only about a third of my total muscles mass), would have required roughly an hour per day — not an impossible commitment, but certainly a major one.
- It may resemble weight loss in this respect. I know heavy people who eat like birds, and I married one who eats whatever she pleases and, as an uncle put it this weekend, she would “disappear if you turned her sideways.”
- At publication, I’m a few days away from turning 40, and I’ve certainly wondered about the effects of age on stretching. What I really need is a time machine, and to do this experiment annually since the age of 10.
- I have often been injured playing ultimate (for instance, see Muscle Pain as an Injury Complication), but never in a way that I think could have been prevented by stretching, with the remote possible exception of a rectus femoris (quadriceps) strain. I’ve had several thumb jams, a nasty acromioclavicular joint sprain, a minor concussion, cracked ribs, etc — all damage from direct hits, which no amount of flexibility would have spared me.
- Actual non-ninja martial artists can probably benefit from flexibility, although (believe it or not) even that can be debated (but is not debated in this article). That leaves gymnasts, for whom flexibility is obviously a great asset, or contortionists, for whom it is the entire point.
- Taylor BF, Waring CA, Brashear TA. The effects of therapeutic application of heat or cold followed by static stretch on hamstring muscle length. J Orthop Sports Phys Ther. 1995 May;21(5):283–6. PubMed 7787852 ❐
This small experiment found that static stretching of the hamstring muscles had the same modest effect on flexibility regardless of superficial heating or cooling.
- No, smartypants, “thixotropy” is not a good reason, but at least I’m impressed by your vocabulary. See Thixotropy is Nifty, but It’s Not Therapy: A curious property of connective tissue is often claimed as a therapy. Thixotropy might account for some minimal improvements in flexibility, but it is logically impossible for it to be an important factor — if it was, we would become obviously more flexible from heating alone, which we definitely do not. I tested this repeatedly during the experiment, and never observed any increase in flexibility just from being hot.
- “Stiff” and “tight” are imprecise, subjective terms: they are symptoms, a kind of mild pain with many possible causes. People who feel stiff often assume their range of motion is actually limited by tight muscles, but this is rarely the case. People with hypermobility also often feel stiff! True abnormal muscle tightness (dystonia) is much less common than the symptom of stiffness, but some milder dystonias do blend right in with other common aches and pains. See Why Do Muscles Feel Stiff and Tight? Maybe your range of motion is actually limited, or maybe it just feels that way.
- Those numbers are a rough estimate of my increased reach as a percentage of muscle length. I’m a short man, only 5’4", so my hamstrings are just about a foot (30cm) long. If I can reach to point x at the start of a session, and x + 8cm at the end, and the limiting factor is primarily the length of the hamstrings, that means that I increased the length of hamstring about 25%. That needs to be arbitrarily reduced somewhat, because clearly the hamstrings are not the only anatomy limiting the movement: some other tissues are probably yielding as well. And let’s make it a range to show some respect for the obvious imprecision here. So let’s make it roughly 15-25% increase in muscle extensibility.
- At first I checked my flexibility as long as several hours later. Finding no sign of my flexibility gains, I began to check sooner and sooner, to find out how quickly I was losing flexibility after each session. I discovered that it was happening amazingly fast: even 5 minutes later, flexibility acquired during the session was already significantly reduced (about 50% of gains). It never took more than just a half hour to lose all my gains.
- On a few occasions, I tried various methods of re-gaining the flexibility acquired during the stretching session. For instance, five minutes after stretching, with flexibility rapidly decreasing, I returned to the hot tub to see if a dose of heating would slow down or reverse the rapid loss of flexibility. It did not. I attempted stretching again immediately, to see if I could quickly (i.e. less than 30 seconds) regain the lost flexibility. I could not. And I attempted to maintain or restore the flexibility by exercising and “staying warm” afterwards. That didn’t work either. Short of continuously stretching, there seems to be no way for me to be more flexible than I am at baseline.