But of course stretching proponents don't make such a claim anyway. So what are their claims, and how do these fare when scientifically tested and scrutinized closely?
Fortunately, the most common beliefs about stretching and knee pain happen to appear in one place (how convenient!): Say Goodbye to Knee Pain by Marian Betancourt and Jo Hannafin. Dr. Hannafin appears to be a prominent orthopedic surgeon; Betancourt has written books on health and women's issues. The copyright is 2007, so the book certainly isn't outdated.
Let's walk through the purported benefits of stretching, one by one. Betancourt and Hannafin are represented by bold italics; I follow in (mostly) normal type.
1. Stretching is critical to increasing flexibility of your muscles ...
Yes, it's true that stretching helps increase flexibility. It's also true that if you have someone constantly stretch out your neck every day (for many hours at a time), you might be able to achieve this:
The point being: there are lots of things that are true, about stretching and about many phenomena in the world at large, but the larger question is, why is the end result desirable? In the case of stretching, who really needs greater flexibility, outside of a normal range? (Paul Ingraham makes this point and many others in his excellent, fact-based analysis of stretching, which I recommend.)
But what about professional or even serious athletes? They aim to compete at the highest levels. Don't they need to be more flexible?
Certain athletes, such as ballerinas and gymnasts, obviously benefit from stretching. Which is kind of logical, if you simply watch their routines/dances, which include bending the body into positions that are hard to attain, even for someone with superior flexibility.
Most sporting activities don't resemble ballet and gymnastics, though. For other athletes, such as cyclists, sprinters and weightlifters, stretching has been shown to impair performance.
Example: four minutes of static stretching had the effect of slowing down sprinters in a study reported in the February 2009 issue of Medicine & Science in Sports & Exercise ("Effects of Static Stretching on Repeated Spring and Change of Direction Performance").
2. Stretching reduces your risk of injury during exercise or everyday activities ...
This claim has been thrown seriously into question.
In Australia, a year-long study of 2,600 soldiers found the same rate of injuries among those who stretched their leg muscles before exercise and those who didn't. On one message board I came across (a stretching debate was going full tilt), a poster derided this study's findings, saying that soldiers wear combat boots and he doesn't.
Okay then, try this on for size: the Centers for Disease Control and Prevention conducted a mass review of 350 stretching studies over four decades. And it also concluded there's no evidence that stretching prevents injuries.
3. Initially, stretching is important because it warms up the muscles and readies the body for exercise ...
Paul has the best line by far on this claim, which is more than faintly ridiculous on its very face. He says, "That's like trying to cook a steak by pulling on it."
What's ironic is that stretching advocates apparently have figured out as much -- though they haven't connected the dots yet. Listen to this guide at About.com (you can find similar thinking in plenty of other places, but this is the first offender I chanced upon):
Always warm up before you stretch. It's a bad idea to stretch cold muscles.But a stretching fanatic might rightly wonder: "Wait a second. Isn't that why I'm stretching? To warm them up? So I have to do some other activity to pre-warm them? What the heck's going on?"
The truth is, the most sensible way to really warm your muscles isn't to stretch. It's to do your intended activity at half-speed or half-force (i.e., jogging slowly to prepare for running a race).
This will increase blood flow to muscle tissue, boost the temperature of the tissue, and increase the range of motion in an activity-specific way. Stretching won't.
4. It is also important to stretch after you exercise or are active, to ease the tension in your muscles ...
I'm not quite sure what this claim is, but let's say the authors are advancing the "stretching prevents the onset of muscle soreness" theory. That's a common belief.
However, an analysis of ten randomized trials that appeared in the Cochrane Database of Systematic Reviews disputed this conclusion. Stretching before exercise or after had little or no effect on how sore someone's muscles felt.
Paul Ingraham quotes a clever line here: "Only soreness can prevent soreness." In other words, soreness is part of the price you pay for training, and increasing loads, and taxing muscles to get stronger.
So there you have it: four big stretching claims to approach with a good dollop of skepticism.
NEXT TIME: So what is stretching really good for? There must be something, right?