Archive for February, 2010

Which winter sports offer the best workout?

February 11th, 2010
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This week’s Jockology column gets into the Olympic spirit, taking a look at four winter sports: snowboarding, cross-country skiing, snowshoeing, and downhill skiing. The question is, how do they stack up as workouts? Beyond the obvious (XC skiing is a great aerobic workout, downhill works your core balance muscles), there are some unexpected nuggets. For example:

…a study published last year in the European Journal of Applied Physiology made a surprising observation: a short test of upper-body strength lasting as little as 10 seconds provided better predictions of performance in a 10-kilometre classic ski race than a test of peak oxygen uptake, which measures aerobic endurance.

In other words, the arms are more important than you might guess. In fact, they provide “up to half the power going uphill during skate skiing, and up to a third of the power going uphill with classic style.”

Other random facts: snowshoeing in powder doubles your oxygen consumption compared to going at the same pace on packed snow. And snowboarders have good bone density, thanks to the high loads on their limbs — and possibly thanks to the whole-body vibration offered by a fast ride.

To read the whole piece, click here (and then click on the graphic to see the whole piece, which is presented as an infographic).

[Note one correction: the data for snowboarding and cross-country skiing got reversed. Recreational snowboarding typically takes about 5-6 MET, while recreational cross-country takes 7-9 MET.]

Stretching is bad for power… and endurance running

February 11th, 2010

[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.


How fast can you build muscle and strengthen tendons?

February 9th, 2010

There’s an interesting study in the latest issue of the Journal of Strength and Conditioning Research about how quickly your muscles and tendons adapt to exercise — and un-adapt when you stop exercising. (Thanks to Steve Magness for pointing this study out.)

The set-up: 8 subjects did three months of strength training (knee extensions), four days a week, and then stopped training for three months. Once a month, researchers from three Tokyo universities measured changes in the affected muscles and tendons, using high-voltage electrical stimulation, ultrasound, MRI and other techniques.

The results: The subjects were significantly stronger after two months, mostly because of better neural activation. The muscles didn’t get bigger until after three months. The tendons also didn’t get significantly stiffer until after three months.

When the subjects stopped training, the pattern was reversed. After just one month, muscle size dropped back to pre-study levels, while strength stayed significantly higher even three months later. Tendon stiffness dropped to pre-exercise levels after two months.

So what does this tell us? First of all, you need to start pumping iron at least three months before you hit the beach. But more generally, it confirms that tendons adapt more slowly to training than muscles (and then lose training more quickly than muscles). This, the authors hypothesize, is because tendons have slower metabolism — as mediated by blood flow and oxygenation — than muscles.

From a practical point of view, this tells us that there’s a period of mismatch after starting a new training program, where the muscles have adapted but the tendons haven’t yet caught up. This creates a risk of, for instance, Achilles tendon ruptures. The solution? Be cautious. Maybe start that weights program four months before beach season, so you don’t have to push it quite as hard.

Cooling your palms enables you to bench press more weight

February 9th, 2010

Another result from the Department of Weird and Unexpected Ergogenic Aids… A forthcoming paper in Medicine & Science in Sports & Exercise, by researchers at the University of New Mexico, finds that cooling your palms between sets of bench press allows you to lift more weight.

The details: 16 subjects performed four sets of bench press at 85% of one-rep max, with three minutes rest. Between sets, they stuck their hands in a Rapid Thermal Exchanger, which heats or cools while applying a negative pressure. Their palms were either heated to 45 C (113 F), cooled to 10 C (50 F), or left at room temperature. Sure enough, they lifted more when their palms were cooled, including a remarkable 30 percent increase in the second set.

So what does this tell us? Well, for one thing, it tells us that people are going to start buying Rapid Thermal Exchangers, or at least bring ice packs into the weight room. But more interestingly — and this is becoming quite a theme on this blog — it adds new evidence in support of the “central governor” model.

If cooling our palms (which are far away from the muscles involved) allows us to lift more weight when lifting to failure, this tells us that the “failure” wasn’t due to some mechanism in the muscle fibres themselves. Instead, when the input to the central nervous system was altered by triggering cold sensors far away from the relevant muscle, the shut-down signal didn’t get sent to exhausted muscles quite as soon. It’s far from clear exactly what’s happening with this weird effect, but the researchers are quite confident that it has something to do with centrally mediated nerve signals — and thus adds support to the idea of a central governor.


The physiology and biomechanics of “skyscraper running”

February 5th, 2010

You’ve seen the news stories about races up various tall buildings like the C.N. Tower and Empire State Building… Now, in an upcoming issue of the Scandinavian Journal of Medicine and Science in Sports, you can finally learn all about the physiology of these races!

pirelli-buildingIt’s actually a pretty interesting paper. The researchers (from the University of Milan) do a general analysis of 36 world stair-climbing records for buildings ranging from 48 to 421 metres high. They also collected a bunch of data from a specific race in Milan (up the Pirelli Building, a model of which is shown on the right), and compare their results to a mathematical model of stair-climbing.

The reason the sport is so well-suited to this kind of analysis is that stair-climbing is fairly simple, biomechanically speaking. We don’t store elastic energy in our legs with each stride — our main task is simply raising our centre of mass from the bottom of the building to the top. (To be precise, the researchers calculate that 80.4% of the energy expended by racers goes directly into counteracting gravity. Just 4.5% goes to accelerating limbs with respect to the body, and the remaining 15.1% goes into the turns between flights of stairs.)

So what’s the take-away message from this research? I’m not sure. Certainly this conclusion doesn’t sound too earth-shattering:

Our studies suggest that the best athletes are those who do not show any sudden speed change, and therefore that athletes must wisely dose their initial effort in order not to jeopardize the rest of the performance.

Still, reading the paper made me want to try one of these races. Apparently they demand a mix of aerobic and anaerobic energy, much like middle-distance running. And then there’s this:

Another attractive aspect relates to the presence, in most skyscrapers, of handrails that maximize the muscle mass involved and, consequently, the mechanical/metabolic power of the ascent, conferring the race with a feel of a global, maximal effort as in rowing.

“Global, maximal effort” — sounds like fun!

Vitamin D study looking for participants

February 1st, 2010

I’ve spent quite a bit of time reading the research on supplements over the past few years — and frankly, the more I read, the less inclined I am to use any. But there is one supplement I’m taking right now (having started a few months ago), and that’s vitamin D. I’ve heard enough enthusiasm from researchers I trust, and seen enough suggestive results, to decide that it’s worth a try — especially during the depths of a Canadian winter.

So why should I expect vitamin D to turn out any differently from all the other “miracle vitamins” that have preceded it and then been debunked? That’s the question that Tara Parker-Pope tackles in this entry on her Well blog. Her main point:

Although numerous studies have been promising, there are scant data from randomized clinical trials. Little is known about what the ideal level of vitamin D really is, whether raising it can improve health, and what potential side effects are caused by high doses.

And since most of the data on vitamin D comes from observational research, it may be that high doses of the nutrient don’t really make people healthier, but that healthy people simply do the sorts of things that happen to raise vitamin D.

Obviously, we need to figure these things out — which is where a new study comes in. The VITAL study is currently enrolling 20,000 older adults to take part in a five-year, placebo-controlled trial of vitamin D and omega-3 fatty acids. They’re looking for people all over the U.S. (no clinic visits are required, and all the pills will be mailed). If you’re interested, the details are here.

For now, I’ll keep taking vitamin D. But it’s worth remembering where the current research stands — and that many previous “miracle vitamins” have failed to pass the hurdle represented by the VITAL study.