Tuesday, July 17, 2007

Stretching Myths


In the Ottawa Metro today there is a full page article on summer sports injuries with a large photo of a woman stretching. A Dr. Douglas Stoddard, a sports therapist, has a large quote in the article stating "the biggest reason people get injured is flexibility or loss of it." I have heard lots of conflicting information about stretching before exercise and it's benefits on injury prevention. A quick search on Pubmed however reveals that there is little doubt that stretching before exercise has no impact on the frequency of injury. A sample of articles: 1, 2 and 3. It is no wonder how myths like this are so prevalent considering the article in the metro quoting an authority on sports injuries. This also gives me a great excuse to maintain my inflexible figure, and is probably a great geeky pick-up line next time you see someone stretching.
However, the stretching institute begs to differ.
Of course there are other reasons for maintaining physical flexibility.


20 comments:

Bayman said...

I think what these types of studies point out is that many people don't understand the point of "stretching" and how to use it. First of all, useful "stretching" of muscles is just one component of a proper warm-up which definitely does prevent injuries during rigorous and dynamic physical activities (but is useless in isolation). Many people however, have been taught that "stretching" means forcing and holding cold muscles in a bunch of awkward positions and then you're ready to go. To properly prepare for activity means slowly increasing muscle temperature, increasing heart rate and circulation, and gradually adjusting muscles and joints to the increased range-of-motion they will have to deal with during the upcoming activity (static and/or dynamic "streches" are one way to do this). But certainly static stretching of cold muscles is useless, if not damaging.

Second point is that flexibility does increase performance and prevent injuries. However increasing and maintaining muscle flexibility is not achieved by a couple of minutes of the above-mentioned stretching before activities, but through a long term, multi-faceted program. The flexibility of different muscle groups must be balanced, and strength maintained to hold things together.

The realization that muscle flexibility and strength can be actively increased and that this is beneficial to performance in virtually every sport, has been the reason for the drastic increases in human athletic performance over the second part of the twentieth century. We are still seeing the effects of this revolution today, with new world records being set constantly, although advances in equipment and drug technology are increasingly playing a predominant role.

rob said...

there is many claims here that you don't provide evidence for.
If you check pubmed there is articles suggesting that there is little evidence that even warming up is injury preventative. Altough I'm sure you're right that it is good for performance

Bayman said...

Acutally, there's lots of pubmed "evidence" either way. So I base my interpretations mainly personal experience and observations derived from pretty much daily experimentation over a 15-20 year time period.

Observations made under controlled lab can be interesting, but if they don't jive with observations made in the real world, than who cares?

If I observe the sky to blue, then it's blue. Even if there were no scientific literature on pubmed containing the results of experiments showing that the sky were blue, or why it was blue, it would still be blue. Similarly if I puke every time I eat carrots, than carrots can make people sick, whether or not statistics found on pubmed support this idea or not. It is the science that needs to be updated, not reality.

Real world observation is the only thing we have as a guide into new realms of scientific discovery. The question has to come from the real world to be relevant. Questions or facts that originate in the lab are useless. The lab is a tool to help us understand and appreciate real world experiences.

Anyway people should read all the ideas that are out there in the scientific literature learn what they can from others who have relevant experience and then more importantly, try things out themselves before making conclusions. But certainly potentially beneficial activities that are practiced by virtually all highly experienced "expert" practitioners should not be rejected just because the benefits cannot always be recapitulated in unrealistic laboratory experiments.

Bayman said...

This debate also demonstrates the danger of placing false value on negative results. An experiment that does not support a hypothesis is meaningless. You cannot prove a negative, as it is impossible to prove that you have actually done the right experiment.

Anonymous Coward said...

You're spreading a couple of misconceptions:
-Firstly, personal experience is anecdotal, and is not "reality". A color blind person might think trees are red, but that does not make them red. The key to science is not experience but independent reproducibility.
-Secondly it is possible to prove a negative provided that the subjects are in a discrete number with a discrete amount of states that are mutually exclusive. For example roll a 6 sided dice, you can prove the result cannot be 7. Mathematics actually has a great deal of negative proofs.

Bayman said...

Yes mathematical proofs are one thing, using an experiment to disprove an assertion pertaining to the real world is impossible. (Maybe because mathematics is a perfect abstraction, whereas experiments are designed and performed by imperfect human beings??)

Also, I agree that one person's experience is not reality - many people must reach a consensus to determine objective reality. That points out another flaw in this debate - it is based on the categorical assertion that ALL forms of "stretching" or warm up are useless as a preparation for ALL types of activity. It is difficult to reach a consensus on such a broad-sweeping hypothesis either through personal real world experience or lab experiments, because people it leads to ambiguity. We all have different personal experiences (or design different experiments) which would lead us to different but equally valid conclusions regarding the truth of an assertion when it has been stated too broadly. In this particular case, the value of warm-up activities varies greatly amongst different types of activities and how they are performed. For example a warm-up (which includes "stretching" of the muscles) is much more important for dynamic, high-paced sports that put joints through extensive range of motion (ie hockey, soccer, gymnastics) than sports with highly repetitive, more limited types of movement (ie cycling, to some extent swimming). At the extreme, without the flexibility enabled by advanced muscle "stretching" programs, the execution of certain types of movements demanded in gymnastics and dance is physically impossible for the untrained. Also the intensity of competition plays a role - during a recreational activity, one can simply replace the warm-up by a slow build-up to activity. At elite or professional levels of competition, maximal performance is demanded as soon as the contest begins, hence the need to use a warm-up as a method to acclimatize the body to the dynamic movements it will need to perform (to avoid injury), while introducing minimal fatigue.

So while I disagree with the original categorical assertion, I agree that there are certainly contexts where "stretching" and even the warm-up concept in general, is of little value and potentially counter-productive. In other situations, "warming-up" the body is required for maximal performance with minimal risk of injury.

Anonymous Coward said...

So basically you only agree with scientific findings if they confirm your opinion. A randomized trial can convince you that a drug shouldn't be approved to treat cancer, but not that stretching should not be recommended to reduce injury.

Bayman said...

A randomized trial showing that a drug has no effect would mean to me no that evidence showing efficacy has been uncovered TO DATE. It does not mean that the drug does not, under any circumstance, work.

An experiment with a negative result leaves two possibilities 1) The drug has no effect under any conceivable circumstance or set of experimental conditions. 2) The drug does have a beneficial effect under some set(s) of conditions which has simply not yet been tested by experiment.

Since the number of conceivable sets of experimental conditions under which an assertion might be tested is for all intents and purposes infinite, one can never claim to have tested them all and therefore general assertions cannot be derived from negative experimental findings.

This also points to the obvious, but often forgotten notion that scientific theories and our understanding of the universe should not remain static, but are always subject to revision in light of new experimental facts.

Alfred Russel Wallace said...

One can only prove something to be false. One cannot prove something to be true...

Bayman said...

I'm so confused.
But if you mash these concepts together you get:

1) Negative results are meaningless.
2) The only meaningful experiments are those which falsify a hypothesis.

Therefore,

3) Only positive experimental results that disprove the hypothesis are meaningful.

Although I'm not exactly sure what "positive results" means anymore, although I'm pretty sure it means something...

Bayman said...

Ow. Peirce and Popper make an ugly couple.

Bayman said...

Does a theory become more likely to be correct every time it is tested and not falsified? If so, I suppose there is also value in a result that fails to falsify the hypothesis...

Bayman said...

I think this quote from Popper gets at the true essence of science:

"Science must begin with myths, and with the criticism of myths; neither with the collection of observations, nor with the invention of experiments, but with the critical discussion of myths, and of magical techniques and practices. The scientific tradition is distinguished from the pre-scientific tradition in having two layers. Like the latter, it passes on its theories; but it also passes on a critical attitude towards them. The theories are passed on, not as dogmas, but rather with the challenge to discuss them and improve upon them."

Maybe the best thing a scientist can do is create the most elaborate, complex illusion possible, making broad and magnificent claims that grab the attention of the masses by prodding at concepts central to the human perception of self. In doing so, the scientist presents the audience with a puzzle to solve, and in so doing they discover for themselves some new understanding of their universe, rather than being told to simply accept without question the wisdom of a single thinker. The grander the illusion, the more is learned.

Kevin Z said...

Your comment on the uselessness of negative results irks me. Negative results are very important because it can relate to how a question was approached or the experimental design. You might fail to reject the null hypothesis because of the design, but other times you might be asking the wrong questions to achieve 'positive results'. Certainly I can think of scenarios where negative results are important. When a drug is found to have no significant effect compared to a placebo, it saves many consumers time and money and potentially side effects.

I have talked before about creating an online, open access Journal of Negative Results. Its only reviewed for design and people can't comment on studies and make suggestions.

Bayman said...

Now would be a good time to clarify what I meant by positive and negative results. I think positive has been taken here as "what the researcher wants to find". I guess what I was trying to say by "positive" was a result which differs from the control, whereas "negative" would show no difference.

So using the drug example, one can always argue that a "negative" result where a drug shows no difference over placebo is inconlusive; maybe the drug is not delivered to the proper location, maybe the wrong cohort of patients were tested, maybe the the drug was administered at the wrong time of day or incorrect lunar cycle, who knows. So you can't make with 100% certainty the generalized assertion "The drug offers no benefit over placebo". However if you see a difference (a "positive" result), you can say with absolute certainty that the drug can offere a benefit.

kamel said...

It's true that negative results remain inconclusive (I was taking 'positive' and 'negative' as you defined them here throughout the discussion), but as McB has famously asked in WIP, how many negatives does it take before you reject your hypothesis?

As someone who has published negative results (an obvious source of bias), I'm certainly inclined to agree with Kevin Z that they're not without value, at least insofar as they can drive critical analysis of existing experimental evidence.

Anonymous said...

Whether to stretch before or after activity is indeed controversial. However increasing your general flexibility is proven to help prevent injuries to the muscles.There is no question about that. If you are typically tight and you ask your muscles to do more than they can in a shortened state, you will tear or strain them. Incresing your flexibility will make those injuries less likely.

doc_bay said...

For those that really believe that "stretching" is the correct thing to do for performance, injury prevention or whatever... I want you to tell me when did you ever see a horse trainer or wild animal go through these gyrations that you "stretching" fanatics go thru based upon "your" preconceived notions for 15-20 yrs of bad habits? A wild animal during the heat of a battle or chase surely does not "stretch" to get their bodies ready for better performance or prevent an injury. Those that continue to perpetuate those antiquated beliefs are the same people that want to continue doing the forced exercises they learned in athletics or the military. Exercise science tells other wise.

viagra online said...

I lost my flexibility some years ago and I'm not really sure if I would can get it again.
Nice article, thanks for sharing.

xlpharmacy said...

It was an interesting article, I had read the same, and I thought there were kidding about the sports injuries and its implications but I was completely wrong !