injuries – Page 4 – Sweat Science

February 11, 2010March 24, 2010

Stretching is bad for power… and endurance running

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- Alex Hutchinson (@sweatscience)

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[UPDATE – March 24, 2010: for further info on this study, including an interview with the author, see this post.]

Among the latest batch of papers accepted for future publication in the Journal of Strength and Conditioning Research is one on the effect static stretching during warm-up on jumping performance, by researchers from the University of Milan. It shows that stretching before exercise makes you jump lower, more slowly, and with less force. Ho-hum, right? Anyone who cares about this stuff has seen these studies before.

(For the record, what’s new in this latest study is that it looks at different joint angles. We already knew that power from full knee extension — e.g. in sprinting from starting blocks or playing football — was reduced. Now we know other angles, like you might encounter in swimming, basketball, soccer and so on, are also compromised.)

But for many people, these studies don’t carry much weight. The typical attitude is summed up by running guru Steve Boyd on his excellent blog:

Although I hedge my bets by not making a religion of stretching, I count myself among those millions who are convinced on the pure level of “feel” that flexibility work enables them to run further and faster, and cope with injuries better. And I think one day science will discover the secret of what many runners “know” deep in their fibers.

And to be fair, most of the existing studies look at explosive power rather than endurance. So I was definitely interested to see another study on the JSCR site that, for the first time, focuses on the effect of static stretching on endurance performance. (There was a study last year that found that less-flexible runners tend to have higher running economy, but it didn’t look explicitly at stretching.)

Lo and behold, stretching before a run makes you run more slowly and less efficiently.

The basic details of the study, which comes from Florida State University: 10 trained distance runners performed two one-hour runs, once with stretching before (four 30-second reps of five basic stretching exercises) and once without. The one-hour runs consisted of 30 minutes at a set pace (65% of VO2max) during which running economy was measured, then 30 minutes going as fast as they could to see how much distance they could cover. The non-stretchers burned ~5% fewer calories in the first part of the experiment, and ran 3.4% farther in the second part of the experiment.

I won’t get into the debate about what causes this. It may have to do with the energy storage abilities of floppy tendons, or the torque-producing capabilities of stretched muscles fibres; this study doesn’t address that. I’m also not making any pronouncements about the role of stretching in general — after all, it’s still very possible (though highly controversial) that a regular stretching program might reduce injury rates.

But I will say this. Static stretching may feel good (possibly in part because so many of us were brought up believing in it), but given the steady accumulation of evidence, you’d be a fool to keep it as part of your warm-up routine before a race. Or any type of athletic competition, for that matter, other that those where range of motion is a key factor, like gymnastics or hockey goaltending.

January 17, 2010

Platelet-rich plasma therapy: just another placebo?

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- Alex Hutchinson (@sweatscience)

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“Platelet-rich plasma therapy” is a pretty hot topic these days, what with sports doc Anthony Galea (who has performed the technique on countless professional athletes) under the microscope because of a criminal investigation, and recreational athletes getting in on the action too. It’s a pretty simple concept: extract the patient’s blood, spin it in a centrifuge to concentrate the platelets (and ditch the red blood cells), then re-inject the platelets at the injury site (e.g. Achilles tendon, tennis elbow, other tendon injuries).

There have been some encouraging studies over the past few years, but a discordant note has just emerged in the Journal of the American Medical Association. Dutch researchers injected 54 patients with Achilles tendon problems, and followed up with them over the course of 24 weeks. Sure enough, the patients improved on measures of pain and activity level — the problem is, half of them were injected with a placebo, and there were no statistical differences between the two groups.

Needless to say, this doesn’t prove that the procedure doesn’t work. But it should throw a bit of cold water on hopes that it would be a miracle treatment.

January 9, 2010January 10, 2010

Is physiotherapy useless?

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- Alex Hutchinson (@sweatscience)

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Gina Kolata has another debunking-conventional-wisdom Personal Best column in the New York Times, this time taking on physical therapy (or physiotherapy, as it’s known here in Canada). I’ve really appreciated some of her previous articles on stretching, cool-downs, massage, lactic acid, and so on. This one, I was less impressed by. She writes:

When I’ve gone to physical therapy, the treatments I’ve had — ice and heat, massage, ultrasound — always seemed like a waste of time. I usually went once or twice before stopping.

To me, this is sort of like saying “Yeah, I’ve tried antibiotics several times, but it never seems to work for me, so I always just take the pills for a day or two and then throw the rest away.” Any successes I’ve had with physical therapy tend not to be the “fix pain in two weeks” category, but more like “spend six months correcting some subtle weaknesses and imbalances in order to avoid repeating the injury you just had.” It’s a long-term investment.

That being said, the article has some interesting information about which treatment and recovery modalities actually have solid evidence behind them (not many). I’ve written about heat and ice and massage before — the fact is, if we limited ourselves to the modalities that have solid peer-reviewed evidence, we’d all just be lying in bed for a few weeks every time we got injured. So much as I like evidence-based medicine, I think we have to be realistic about the current state of knowledge.

January 8, 2010January 27, 2010

Running shoes are worse than high heels (unless you actually read the study)

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- Alex Hutchinson (@sweatscience)

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In the comments section of yesterday’s post, John Lofranco raised the topic of a subject that has been popping online and in newspapers over the past few days. You may have seen the headlines: “Running shoes are more dangerous than high heels” and so on. Here’s the press release, and here’s the full text of the study itself, “The Effect of Running Shoes on Lower Extremity Joint Torques,” by researchers at the University of Virginia. Here’s the key part of the press release:

In a study published in the December 2009 issue of PM&R: The journal of injury, function and rehabilitation, researchers compared the effects on knee, hip and ankle joint motions of running barefoot versus running in modern running shoes. They concluded that running shoes exerted more stress on these joints compared to running barefoot or walking in high-heeled shoes.

From what I can tell, this is solid research that suffered from the “broken telephone” effect, being successively distorted at each step. First, there’s the data they measured — useful stuff that sheds light on how our legs work. Then there’s the scientific paper, which in my opinion stretches the conclusions a little farther than the data currently warrant. Then there’s the press release, written by a PR person at the journal, which stretches things even further (the study, for instance, did not include any high-heeled shoes, and no direct comparisons between running shoes and high-heeled shoes were possible). Then there are the press articles, which rely on the press release… (There’s also this: “In July, [Kerrigan] left the University of Virginia to start her own company, JKM Technologies LLC, which will focus on developing her shoe in coming years.”)

Amby Burfoot of Runner’s World, in his Peak Performance blog, has written an excellent post in response to this study that is essential reading for anyone interested in running injuries and the role of shoes. As usual, it’s a nuanced point of view that neither praises nor buries the research. He points some of the leaps — the difference between measured torque in the knee and observing arthritis, the mismatched comparison between walking and running forces, the downplaying of the role of stride length. His main message is that this is a very complex field of research where little is known, so we should be open to new results but avoid gratuitous oversimplification. It’s definitely worth a read.

November 18, 2009

Stress fractures: reducing stride length and the role of muscle

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- Alex Hutchinson (@sweatscience)

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A couple of interesting studies about stress fractures in the December issue of Medicine & Science in Sports & Exercise.

First, researchers from Iowa State University looked at the effect of stride length. Basically, the idea is that if you shorten your stride, you’ll have more footstrikes per mile (and thus more impact jarring your bones) but each footstrike will be a little gentler. So which effect predominates? The researchers had 10 runners run at their normal stride length, and with a 10 percent reduction in stride length, measuring the relevant forces with motion-capture cameras and force plates. They then used a computer model based on bone damage and repair mechanisms to estimate the risk of stress fracture for both groups. The conclusion: shortening your stride length by 10 percent reduces stress fracture risk by three to six percent!

The clinical implications for these results are clear [they write]. Those runners wanting to decrease their likelihood for stress fracture can do so by reducing their stride length by 10%. This reduction would also allow for runners to run an additional 2 miles [per day] and maintain the same [fracture risk].

In general, I’m not a big fan of trying to meddle with your running form, thanks in part to studies like the one I wrote about here. But overstriding is apparently a pretty common issue, and prominent coaches like Jack Daniels have advocated increased cadence (and thus shorter stride) as a way of running more efficiently. So maybe there’s something here…

In the same issue of MSSE, researchers from the University of Minnesota examined the bone strength and body composition of 39 female distance runners, (slightly less than) half of whom had a history of stress fractures. To nobody’s surprise, the tibia bones in the stress fracture group were smaller by seven to eight percent, and weaker by nine to 10 percent. What’s interesting, though, it that the bone differences were exactly in proportion to the size of the muscles in the same area, and there was no difference in bone mineral density. What this suggests is that the best way to avoid stress fractures is to make sure you have enough muscle on your legs — presumably by doing weights and (it goes without saying) eating enough.