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Archive for January, 2010

Jockology: good (and bad) research into performance mouthpieces

January 28th, 2010

I have to admit, I was very, very skeptical when I read this report in the New York Times about “performance mouthpieces” that would instantly boost strength, power, endurance, flexibility, reaction time and so on. Alarm bells ring for me when a researcher offers evidence like this:

Previously she “had been happy with running 10-minute miles,” she said, but wearing the mouthpiece, she consistently ran a mile in as little as 8 minutes. “It was pretty astounding to me,” she said. “I didn’t feel as tired as when I ran the 10-minute-per-mile pace.”

So I figured I’d look into the research behind the claims for a Jockology column, which appears today.

What I found was a surprise — in both directions. There was some surprisingly good research that suggests there may be a real effect here. And there was some surprisingly bad research that any company should be embarrassed to promote. The main research cited by Under Armour to back up the claims for its mouthpiece come from a special issue of the far-from-prestigious Compendium of Continuing Education in Dentistry. And not just any special issue — every article in the issue is written by someone who is either an employee or paid consultant of Bite Tech, the company that developed Under Armour’s mouthpieces. This is not research, it’s advertorial.

Here’s an example of what this means, as I describe in the Jockology piece:

The results are interpreted rather generously. What’s described as “a definite trend for lower cortisol” turns out to mean that cortisol levels dropped in only 11 of the 21 cyclists in the study – barely more than half. A follow-up study of runners in 2009 also failed to find any statistically significant change in cortisol.

On the other hand, there is a placebo-controlled, double-blinded crossover study, funded by Makkar Athletics, that found an increase in vertical jump and power in a 30-second cycling test. So, despite my skepticism, there may be something there after all…

Lieberman says barefoot running is better than shoes

January 27th, 2010

This is going to make a big splash. A paper by Dan Lieberman — the Harvard anthropologist who made headlines with the argument that long-distance running was a key evolutionary driver in humans — in tomorrow’s issue of Nature argues that barefoot running is better than modern running shoes. Here’s how the Associated Press is reporting this story:

Harvard biologist and runner Daniel Lieberman had a simple question: “How did people run without shoes?”

The answer he got is: Much better.

At least running barefoot seems better for the feet, producing far less impact stress compared to feet shod in fancy, expensive running shoes, according to a study by Lieberman in Thursday’s issue of the journal Nature. The study concludes that people seem to be born to run—barefoot…

What great timing, you might think. After all, it was just last week that I blogged about Mark Plaatjes’ thoughts on barefoot running — and two of his key statements, which I agreed with, were:

4. There are no clinical trials that show an effect of barefoot/minimalist running for a prolonged period of time.
5. There are no research studies that prove that wearing traditional running shoes increases injuries or that barefoot/minimalist running reduces injuries.

So does Lieberman’s study fill this gap? No. What he found is that his subjects strike the ground with three times more force when they’re wearing cushioned running shoes compared to running barefoot. This is reminiscent of the study that made waves a few weeks ago (which I blogged about here) that made the convoluted claim that running shoes are worse than high heels. What we’re dealing with in both cases is very indirect measures that may or may not have some connections to the outcomes that matter to us — i.e. pain and injury. I really don’t care how many Newtons of torque my patella is feeling if it doesn’t result in any injury or discomfort.

Now, I haven’t seen the study, so I’ll be very interested to read it when it comes out tomorrow. But given the current wave of popularity surrounding barefoot running, I have a sinking feeling that this is just the beginning of the storm — we’re going to see a whole bunch of studies coming out, accompanied by press releases and news stories, that capitalize on this interest without really telling us what we want to know. Hopefully there are also people doing the long, painstaking, prospective research that would really shed new light on this question.

I don’t mean to sound too skeptical here. I think a lot of what’s said about barefoot running makes very good intuitive sense. If I was growing a batch of test-tube babies to create a distance-running army, I’d probably have them avoid shoes during their formative years to develop the stride we see in Kenyan runners.

But most would-be runners in the Western world are not starting from scratch — and the question of what shoe makes the most sense for a middle-aged, overweight neophyte is still very much open. Even staunch minimalists would acknowledge that running barefoot isn’t an instant miracle cure. (“If you change the way you run quickly ‘you have a high probability of injuring yourself,’ Lieberman says. In general, changes either in running shoes or distance should be no more than 10 percent a week.”)

That may well be true. My feeling, though, is that most people who are REALLY cautious and patient enough that they never change their weekly running distance by more than 10 percent a week will find that they’re able to run successfully in almost anything. It’s like (bear with me here) buying a house to get the financial advantages. We can debate until we’re blue in the face whether owning or renting makes more sense — but for many people, buying acts as a “forced savings” mechanism, since they no longer have any disposable income to waste. Maybe barefoot running acts in a similar way: it forces runners to be cautious and build up very gradually — precisely the approach that works best no matter what you’re wearing.

Tylenol’s pain-blocking boosts endurance performance

January 26th, 2010

To the scientist in me, this is a really interesting study. But to the athlete and fan in me, it seems like bad news. British researchers fed highly trained cyclists acetominophen (Tylenol, as it’s known around here) before a 10-mile time trial. It was a double-blind, placebo-controlled trial. The riders who were fed Tylenol cycled about 2% faster, and had higher heart rate and lactate production (i.e. they were working harder) — but their perceived exertion was identical to the placebo group’s.

To read more about the study and its implications, read this entry in Amby Burfoot’s Peak Performance blog, which includes a Q&A with one of the researchers. The basic interpretation is simple: Tylenol blocks pain, and pain is what makes us slow down during long races. This is an important scientific result, because it sheds light on a red-hot debate about the nature and origins of fatigue. The authors of the study view their results as supporting the “central governor” theory, which argues that our brain subconsciously makes sure that we never let our body get too close to its absolute limits.

This, of course, is not the main message that many athletes will take from the study. A 2% performance boost is nothing to sneeze at for the well-trained athlete, so I expect that many athletes will start experimenting with Tylenol in training and racing. Is this dangerous? I don’t really know. (Gretchen Reynolds wrote an interesting article last summer about the risks athletes incur by overuse of NSAIDs like ibuprofen; Tylenol is a different class of drug.) But I have to admit: whenever I see a study of a potentially performance-enhancing pill, I cheer when the results come up negative, because (in my view) it keeps the sport a little simpler.

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More quercetin: a (tiny) endurance boost

January 22nd, 2010

Last fall, an excellent University of Georgia study failed to confirm the endurance-boosting effects of the supplement quercetin that earlier mouse studies had suggested. Now there’s a new study on quercetin from David Nieman’s highly respected lab at Appalachian State University, in the February issue of Medicine & Science in Sports & Exercise — and the news is mixed.

Reading the abstract, you might conclude the double-blinded crossover study was a success: they found “a small but significant improvement in 12-minute treadmill time trial performance” after two weeks of 1,000 mg of quercetin a day. Quercetin is a flavonoid that is thought to enhance the growth of new mitochondria, which is the most significant adaptation resulting from endurance training. So they also performed muscle biopsies, but these didn’t show a significant effect (though there were “insignificant increases”).

When you read the study closely, even the treadmill improvement is a disappointing result. An earlier study from the same lab had failed to find any improvement for well-trained cyclists in 5-, 10-, and 20-km time trials. So they hypothesized that the benefits of quercetin wouldn’t show up for well-trained athletes, who already have a high density of mitochondria. This study specifically enrolled sedentary young adults: the maximal exercise level permitted was 20 minutes, twice a week.

In other words, these were subjects ripe for LARGE improvements. What they found was an improvement of 2.9% in treadmill distance, while the placebo group actually got 1.1% worse. It is statistically significant (barely: P=0.038), but it’s hard to argue that it’s practically significant. For people this sedentary, an occasional walk around the block would have done more. An improvement of a percent of two is only really significant for elite athletes — precisely who this study wasn’t aimed at.

The authors acknowledge that the effect is far smaller than that seen in mouse studies, and they conclude that further research is needed with higher doses and longer study periods. This sounds like a good idea — but until those studies come in, the logical assumption is that quercetin doesn’t offer any practical benefit for people of any fitness level.

Mark Plaatjes on barefoot/minimalist running

January 22nd, 2010

[1/27: For more on this debate, see here.]

Mark Plaatjes, the marathon gold medalist at the 1993 world championships and longtime physical therapist to running stars in Boulder, has posted his thoughts about the current fad for barefoot/minimalist running on Facebook. It’s an interesting read. He starts with five facts that (he says) no one would dispute:

1. Running barefoot/minimalist strengthens the intrinsic or postural muscles in the feet and lower leg.
2. Running barefoot/minimalist increases proprioceptive awareness and balance.
3. Running barefoot/minimalist forces a change in mechanics to adapt to the forces on the feet.
4. There are no clinical trials that show an effect of barefoot/minimalist running for a prolonged period of time.
5. There are no research studies that prove that wearing traditional running shoes increases injuries or that barefoot/minimalist running reduces injuries.

I’d agree with these statements.

He then discusses the distinction between “good” and “bad” heel-striking. People who overstride come crashing down on their heels, braking with each stride. This is bad. But it doesn’t necessarily follow that ALL heel-striking is bad — if you’re running with a short enough stride, so that your centre of gravity is above your heel when you land, that’s a perfectly good stride, Plaatjes says. In other words, not everybody has to become a forefoot striker, despite the claims made by minimalist advocates.

After that, the article starts to ramble a bit, and I’m less clear what his point is. He does make an interesting claim: that 65 to 75% of people are unable to run barefoot because they have inadequate foot structure and mechanics (and he can tell by looking at their feet). He starts to lose me here, since he doesn’t back up this statistic. But I think his first five points (which I quoted above) are a good starting point for any discussion of this issue — because if you disagree (particularly with points 4 and 5), you’ve probably bought some snake oil.

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Canadian Running magazine: Jan.-Feb. issue

January 21st, 2010

A belated note that the Jan.-Feb. issue of Canadian Running magazine is on newsstands now. My top picks for this issue: a hilarious back-page essay by Canadian miling legend Harvey Mitro on runners’ obsession with stopping their watches, and an interesting piece by nutrionist Matthew Kadey on which foods it’s worth paying more for, and which you can skimp on. (For example, he argues in favour of dark poultry meat — a policy I’ve long advocated in order to save $1.19 at Swiss Chalet!)

And, of course, there’s my regular Science of Running column, tackling hyponatremia, deep-water pool-running, “dynamic compression” technology, and other topics.

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When is it too hot to run a marathon?

January 21st, 2010

Ever since the sun-baked fiasco of the 2007 Chicago Marathon, there’s been renewed discussion about how to figure out when it’s unsafe to hold a major road race. In the February issue of Medicine & Science in Sports & Exercise, the medical director of the Twin Cities Marathon, University of Minnesota med school prof William O. Roberts, has an interesting analysis of this question — and he ends up with pretty conservative recommendations.

What’s interesting about his analysis is that he takes a population-level approach: instead of sticking a few representative subjects on a treadmill, he analyzes two large data sets. First, he looks at eight unexpectedly hot races that results in either mid-race cancellations or “mass casualty events” (where the number of patients overwhelms the medical resources available in a community), and calculates the “wet bulb globe temperature” (WBGT) at start time. He finds that WBGT above about 21 C (70 F) is an indicator of serious trouble for marathons at northern latitudes with participants who haven’t acclimatized to the unexpectedly hot weather.

Then he does a more specific analysis for the Twin Cities marathon, plotting the percentage of marathon starters who were either unable to finish or required medical attention as a function of WBGT. (The graph, along with the full text of the paper, is available here.) In this case, he finds that a start WBGT above 20.5 C (69 F) is trouble.

These conclusions contrast with American College of Sports Medicine guidelines allowing starts with WBGT up to 28-30 C (82-86 F) — guidelines based on tests of young military recruits. The key problems are (a) the average recreational marathon runner is not G.I. Joe, and (b) the participants in a northern (latitude greater than 40 degrees) marathon will be less prepared for a hot day than people who live in hot places.

This probably isn’t welcome news for race directors — no matter how hot it is, few participants are going to take kindly to a decision to cancel something they’ve spent months training for. But knowledge is good — and even if a race isn’t cancelled, this is the kind of information that runners themselves should take into account when they’re facing adverse weather conditions.

(A note on WBGT: it’s a scale that takes into account the effects of humidity and solar radiation, as well as air temperature, on humans. As a very rough rule of thumb, if humidity is above about 50%, WBGT will be higher than air temperature; if humidity is below 50%, WBGT will be less than air temperature.)

Pressure during penalty kicks makes you fixate on the goalkeeper

January 18th, 2010

When you kick a soccer ball, it tends to go where you’re looking. The problem is that when you’re anxious, you tend to fixate on threats — the goalkeeper, in this case — and consequently kick it straight at him. That’s the message from an interesting University of Exeter study published last month, which I just noticed thanks to Dan Peterson’s blog.

The players wore special glasses which enabled the researchers to record precise eye movements and analyse the focus of each footballer’s gaze and the amount of time spent looking at different locations in the goal. The results showed that when anxious, the footballers looked at the goalkeeper significantly earlier and for longer. This change in eye behaviour made players more likely to shoot towards the centre of the goal, making it easier for the keeper to save.

The solution? “Research shows that the optimum strategy for penalty takers to use is to pick a spot and shoot to it, ignoring the goalkeeper in the process,” the study’s author says. And to do that, you need to practice, so that the skill becomes so ingrained it no longer requires conscious control, as discussed in this Jockology column.

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Platelet-rich plasma therapy: just another placebo?

January 17th, 2010

“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.

Yoga reduces cellular inflammation marker

January 16th, 2010

I get a lot of questions about the benefits of yoga, and they’re very difficult to answer for a number of reasons. One is that yoga is so diverse — different types of yoga (and different teachers and different classes) offer very different stimuli. Even within a given type of yoga, it’s a very “mixed” activity, working on flexibility, strength, as well as possibly cardio and mental state. Given these challenges, it’s not surprising that there’s a lack of solid research into the benefits of yoga, so I’m always happy to see a study that looks at something more quantifiable than “sense of wellness.”

With that preamble, here’s a press release about a new Ohio State study, which found that women who practiced yoga had lower amounts of a cell called interleukin-6 (IL-6) in their blood. IL-6 is a cytokine (a type of cell produced by the immune system) associated with inflammation, which has been implicated in heart disease, stroke, diabetes and other diseases. Great!

If you look more carefully at the study, though, it’s not quite the smoking gun we’re looking for. For one thing, it wasn’t a “prospective” study that observed changes over time. Instead, they took one group of yoga experts, and compared them to another group of yoga novices. The experts had lower levels of IL-6, but of course it’s hard to know whether the personality (or physical) traits that had led these people to become yoga masters also had other effects that put their bodies under lower stress. The study also looked at how the subjects’ IL-6 levels responded to stressful tests like cold-water immersion and hard math problems. Again, the yoga experts did better, but that doesn’t really tell us anything definitive.

Surprisingly, one test that showed no difference between the novices and the experts was in their physiological response to a yoga session. Here’s what Lisa Christian, one of the researchers, had to say about that:

“Part of the problem with sorting out exactly what makes yoga effective in reducing stress is that if you try to break it down into its components, like the movements or the breathing, it’s hard to say what particular thing is causing the effect,” said Christian, herself a yoga instructor. “That research simply hasn’t been done yet.”

Which is basically what I was saying at the top of this post. Yoga is complicated — and for now, the research looking for its “secret” remains pretty sketchy.