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Archive for May, 2011

Is less really more in warm-ups?

May 31st, 2011

A few people have e-mailed me about this University of Calgary study, (“Less is More: Standard Warm-up Causes Fatigue and Less Warm-up Permits Greater Cycling Power Output”) which has received a bunch of press. It seems to run counter to the message from this blog post a few weeks ago, which argued that a hard effort during your warm-up could enhance performance.

The new study had cyclists perform either a “standard” long warm-up (designed in consultation with elite track cyclists and coaches), or an experimental short warm-up. Then they tested performance, and the short warm-up group had a 6.2% advantage in peak power. Okay, cool. This is valuable information. But let me add two caveats:

  1. What was the “standard” warm-up? It was “about 50 minutes with a graduated intensity that ranged from 60 to 95 per cent of maximal heart rate before ending with several all-out sprints.” That’s one heck of a warm-up. In comparison, the experimental warm-up was “about 15 minutes, and was performed at a lower intensity, ending with just a single sprint.”
  2. What was the performance test? It was a 30-second Wingate test.

Now, bear in mind what athletes are hoping to achieve with a warm-up. According to the paper, it’s:

[I]ncreased muscle temperature, accelerated oxygen uptake kinetics, increased anaerobic metabolism and postactivation potentiation (PAP) of the muscles.

In the blog post a few weeks ago about the “priming” effect of a hard warm-up effort, the focus was on accelerated oxygen uptake kinetics. But in a 30-second sprint, oxygen kinetics have nothing to do with it. We’re talking about two different animals here.

Bottom line: if you’re a track sprinter who spends nearly an hour warming up at up to 95% of max heart rate, then this study tells you something very important. But if your event is longer than 30 seconds (so that oxygen kinetics matter), and your warm-up tends to be shorter and less intense, don’t assume that this study is telling you to shorten it even more!

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Yoga’s dose-response effect

May 30th, 2011

This week’s Jockology column in the Globe and Mail takes a closer look at a neat yoga study that I blogged about last month. I got in touch with Nina Moliver, the researcher responsible for the study, and looked at the data more closely:

When Nina Moliver decided to study the long-term health and wellness effects of yoga for her doctoral research in psychology, one of her professors offered some advice.

“The yoga world doesn’t need more testimonials,” the professor at Arizona’s Northcentral University told her. “The only way you’re going to communicate with the medical community is with numbers.”

Yoga science is a burgeoning discipline, with researchers probing yoga’s effects on everything from stress hormones to skin conditions. But how can a typical four- to six-week study capture the benefits of an ancient mind-body discipline that takes years, if not decades, to master? It can’t, Dr. Moliver concluded – so she decided to take a radically different approach that offers the first quantitative look at yoga’s long-term benefits. And the results of her study are promising for dedicated yoginis…. [READ ON]

One little online extra that I’ll post here is one of the graphs from the study, to give a sense of what the data looks like. Basically, you get data points filling the triangle on the upper left of the graph, while the lower right remains empty.

Here’s how I describe the data in the Globe article:

Interestingly, the most experienced yoginis weren’t necessarily happier or healthier than the happiest and healthiest non-yoginis, at least in the parameters Dr. Moliver was able to measure. “They didn’t find ‘enlightenment’ that others can’t reach,” she says. The biggest differences were at the other end of the scale, in the scarcity of unhealthy or unhappy long-time yoga practitioners.

 

When Nina Moliver decided to study the long-term health and wellness effects of yoga for her doctoral research in psychology, one of her professors offered some advice.

“The yoga world doesn’t need more testimonials,” the professor at Arizona’s Northcentral University told her. “The only way you’re going to communicate with the medical community is with numbers.”

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More evidence that heat is in your head (or neck)

May 27th, 2011

In the last month, I’ve posted about palm cooling, face-warming, and a study that suggested that some of the slowdown we experience in hot weather is attributable to the brain rather than body overheating. The latest addition to this theme: a study on neck cooling, published online in Medicine & Science in Sports & Exercise a few days ago.

The gist: Seven cyclists performed a 15-minute time trial in 30 C heat, after riding for 75 minutes to heat themselves up. They did it once as a control, once while wearing a “cooling collar” (essentially an icepack that fits around their neck while riding), and once with the cooling collar being replaced every 30 minutes to keep it colder. As expected, the cooling collar improved performance in the time trial by about 7% (this has been demonstrated before); but replacing the cooling collar didn’t produce any further gains, even though any cooling effect had disappeared long before the time trial started.

What’s most interesting is that there were no differences between groups in any of the physiological variables they measured — rectal temperature, hormones like seratonin and dopamine, lactate levels, etc. The differences appeared to be purely perceptual:

It has been proposed that during self-paced exercise the intensity is regulated by a complex network of feedback and feed-forward systems regarding the physiological state of the body to allow for the completion of the task within homeostatic limits. The data from the current study and from a previous investigation using the same protocol suggest that cooling the neck enhances preloaded time-trial performance in a hot environment by masking the extent of the thermal strain…

Or, to put it simply, it’s in your head. That doesn’t mean that heat doesn’t have real physiological effects — just that, in most cases, our brains take the heat into account to slow us down prematurely.

strain9The critical core temperature and central governor theories are the two main theories proposed to
explain the impairment in sporting performance observed in hot temperatures and both models propose that there are
mechanisms in place to prevent the onset of a dangerously high internal temperature

How effective are placebos for headaches?

May 25th, 2011

We all know that placebos work (even if we know we’re taking a placebo, as this study showed). But how well do they work? Researchers in the Netherlands did a meta-analysis of 119 headache studies to evaluate the recovery rate among the placebo/control groups. The verdict: 38.5% of patients given placebo pills recovered, while 15.0% of patients in control groups that didn’t receive pills recovered.

This isn’t surprising, of course (though it’s nice to see some numbers to get a sense of scale). But what does it mean? How do we use this information? A recent McGill study found that one in five Canadian doctors acknowledged prescribing placebos to their patients. The German Medical Association, meanwhile, just released a report from its scientific advisory board encouraging greater use of placebos:

“The placebo effect plays a critical role in every day practice,” says Robert Jütte, lead author of the report. Indeed, a survey of German doctors found that half of them had used a placebo before. In the southern German state of Bavaria, the figure was close to 90%. Jütte says that this majority is right: “Every good doctor should have a couple of white or blue sugar pills handy.”

To me, the ideal scenario is that we devote more research resources to understanding how and why placebos work — though of course there’s little incentive (and strong disincentives, in some ways) for pharmaceutical companies to pursue this topic. Is deception really necessary for this effect to work? Or is it possible that, once we understand it better, we’ll be able to harness the power of the brain in a more controlled (and honest) way.?

Launching today: Cardio or Weights!

May 24th, 2011

Today’s the day that my new book, Which Comes First, Cardio or Weights? Fitness Myths, Training Truths, and Other Surprising Discoveries from the Science of Exercise, finally hits stores. It’s my attempt to bring together what we know (not what we think!) about how the body responds to various types of exercise, training, nutrition and recovery protocols, divided in 12 chapters and 111 Q&As. You can read the full Table of Contents here, and there are links to the many places you can order from here.

The initial reactions have been encouraging. Amby Burfoot at Runner’s World gave it a really nice review (and did a brief author Q&A with me); Kirkus Reviews called it “factual, information and empowering.” There will — hopefully — be plenty more reviews and interviews over the next few weeks. [UPDATE: Here's a review from Jimson Lee at SpeedEndurance, and a Q&A with Jonathan Goodman of the Personal Trainer Development Center.]

There are also a few upcoming events I’d like to highlight:

  • I’ll be at the Ottawa Marathon fitness expo from Thursday, May 26 to Saturday, May 28, answering questions and signing copies of the book in the Canadian Running magazine booth.
  • On Friday, June 3, at 7 p.m., I’ll be giving a free talk on the Science of Running at Boutique Endurance in Montreal.
  • On Monday, June 6, I’ll be giving a free talk on the Science of Marathon Training at the Scotiabank Toronto Waterfront Marathon Launch Night at the Downtown Marriott in Toronto. This one’s also free, but you need to RSVP at this page. [UPDATE: this one's now sold out.]

Thanks to everyone who has read and supported the blog over the years!

Is strength training really better than cardio for weight loss?

May 24th, 2011

I did a radio interview today with Angela Kokott on QR77 in Calgary, and one of the questions we discussed was the perennial claim that lifting weights is better than aerobic exercise for burning calories. It’s a claim that isn’t totally crazy — even the most recent American College of Sports Medicine position stand on weight loss reverses earlier stands by acknowledging the possibility that resistance training could contribute to weight loss by elevating resting metabolic rate, increasing fat oxidation, and making people more active generally. Here’s the funky flowchart they use to illustrate this process:

Still, the “evidence statement” endorsed by the position stand is: “Resistance training will not promote clinically significant weight loss.” In other words, it’s a nice theory, but the studies of actual people losing weight don’t back it up.

The reason I bring this up is that James Fell has a good article in the Los Angeles Times that tackles this topic — in particular, taking on the oft-repeated whopper that every pound of muscle burns an extra 50 calories a day. He turns to Claude Bouchard of Pennington Biomedical Research Center, who offers the following breakdown of resting metabolic rate (RMR):

Brain function makes up close to 20% of RMR. Next is the heart, which is beating all the time and accounts for another 15-20%. The liver, which also functions at rest, contributes another 15-20%. Then you have the kidneys and lungs and other tissues, so what remains is muscle, contributing only 20-25% of total resting metabolism.

The punchline, according to Bouchard: a pound of muscle burns about six calories a day while a pound of fat burns two calories a day. Don’t get me wrong: strength training is great for many reasons, and I certainly encourage everyone (including, reluctantly, myself) to do some. But it’s not a miracle weight-loss technique.

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Does fat matter?

May 23rd, 2011

Just a decade ago, our concept of “healthy eating” was so simple and straightforward: fat is bad. These days, not so much. Amby Burfoot’s most recent Peak Performance blog post summarizes the key points from “The Great Fat Debate” held among four highly respected nutrition experts (Walter Willett, Alice Lichtenstein, Lewis Kuller, and Darius Mozaffarian) in the current issue of the Journal of the American Dietetic Association.

There was plenty of disagreement, but some common ground. For example, total fat is less important than the type of fat: saturated fats (e.g. dairy and meat) are less desirable than unsaturated fats (e.g. olive oil). But replacing fats with processed carbs isn’t the answer, and will probably make things worse — which brings up the fundamental problem with this kind of debate. As Harvard’s Mozaffarian puts it:

Dietary recommendations that focus on selected nutrients, such as total fat or saturated fat, are often confusing for the public, result in illogical dietary decisions, and increase the potential for manipulation of nutrient targets by the food industry… If we’re eating an otherwise healthful diet including plenty of vegetable oils, fruits, vegetables, fish, and nuts, it will be much less important what the saturated fat level is.

Or as Lichtenstein (of Tufts) puts it, more simply:

I think we have to stop talking about individual dietary components because when one goes up another goes down.

Given the continuing disagreement about fundamental questions (is cholesterol bad?), it seems pretty clear to me that we don’t have enough understanding of the complex relationship between diet and health to successfully micromanage the ratios of specific nutrients. On the other hand, we have pretty unambiguous evidence about the benefits of certain patterns of eating — like getting lots of vegetables and fruit. Until the research is a little less murky, that’s the approach I’m sticking with.

Arthur Lydiard recording

May 20th, 2011

Bit of an obscure find for distance running fans out there: a three-hour recording of a speech by Arthur Lydiard in 1963 at San Jose State University, with Peter Snell and Murray Halberg throwing in their two cents and answering questions. This was three years after Snell, Halberg and marathoner Barry Magee took gold at the Rome Olympics, and the year before Snell took double gold in Tokyo. It’s on sale at BudWinter.com — Winter was the coach at San Jose State from 1941 to 1970, and he’s the one who hosted the talk and introduces Lydiard.

I’d never actually heard Lydiard speaking; it’s pretty funny in places. For example, Peter Snell’s first 22-mile run with the group:

[With 2.5 miles to go], he started crying like a kid, tears running down his face. And no one would help him. We said, ‘Look, you’ve only got a little way to go, just keep plodding’… He lay on the bed and he sobbed for half an hour like a kid. Now we’re not very sympathetic. We said, ‘Look, Snell, in two weeks’ time you’re going around there again.’

And his thoughts on stretching and other conditioning drills:

I don’t think Halberg or Snell or any of those guys could touch their toes. I honestly don’t. It’s not because I don’t believe in exercises, loosening and stretching. It’s solely because we haven’t got time to do it. And I don’t think it would make them run any faster anyway.

Anyway, a fun little piece of history for any Lydiard fans out there!

Cycling in the heat: knowing the temperature slows you down

May 18th, 2011

You run or bike slower in hot conditions because your body overheats… right? Actually, it’s a bit more complicated than that, according to a neat study from the University of Bedfordshire and the University of Brighton posted online at the European Journal of Applied Physiology a couple of days ago.

Here’s what they did: seven cyclists performed three 30-minute time trials under different conditions:

  1. the control trial, at 21.8 C
  2. the hot trial, at 31.4 C
  3. the “deception” trial, at 31.6 C — but thermometers were “fixed” so that the room temperature was displayed as 26.0 C, and the rectal temperatures of the cyclists were displayed as 0.3 C lower than they really were.

As expected, the cyclists covered ~4% less distance in the hot trial than the control trial. But in the deception trial, the heat didn’t hurt them at all — they covered just as much distance (slightly more, actually) than in the control trial!

This study joins a long-running dispute about exercise in the heat, sparked by work from Ross Tucker and others in Tim Noakes’s group in Cape Town. What Tucker argues is that we don’t slow down because we’re dangerously hot; we slow down to avoid getting dangerously hot: the “central governor” in our brains forces us to slow down before we reach any critical temperature. That’s why, if you do a 30-minute cycling time trial in hot conditions, you’ll already be behind your “normal temperature” pace within the first five minutes, and your brain will be recruiting fewer muscle fibres — even though, at that early stage in the trial, your core temperature is still relatively low.

Tucker argued that this is all unconscious, and your brain monitors the rate of heat storage in your body. Others like Samuele Marcora at Bangor argue that it’s a conscious process dictated by your feelings of discomfort. The authors of the new study view their results as supporting the central governor model, but there are a few interesting wrinkles. In particular, the measured skin temperature of the participants was ~0.5 C lower in the deception trial than in the heat trial for the first 15 minutes. This is a real physical effect, not just “in the head,” which the authors explain as follows:

We speculatively propose that the perceived need for heat dissipation was less during the early stage of the TT in DEC, which caused an involuntary autonomic reflex to reduce peripheral blood flow, resulting in lower [skin temperature]…It appears that a response based on incorrect conscious information may be sufficient to produce a subconscious physiological effect that resulted in an improved performance.

Strange stuff. So any practical benefits? It’s hard to imagine convincing your coach or spouse to give you fake weather reports on race days (or at least, it’s hard to imagine falling for it more than once). On the other hand, this suggests that your beliefs about how weather affects you can actually become self-fulfilling prophecies. If you’re convinced that heat will slow you down, it will. On the other hand, maybe someone like Sammy Wanjiru (RIP) simply wasn’t burdened by the belief that heat would slow him down — which could help explain his otherwordly performance in the heat of the Beijing Olympic marathon.

Training in a carb-depleted state: pros and cons

May 16th, 2011

This week’s Jockology column in the Globe and Mail takes a look at some of the benefits and risks of working out in a carbohydrate-depleted state:

For decades, sports nutritionists have been devising ever more sophisticated ways to ensure your body is perfectly fuelled before, during and after every workout. With gels, bars and belt-mounted drink bottles, you can have calories within reach no matter where you are.

But what if quaffing fewer carbs and calories – or even none – resulted in a better workout?

At a recent sports nutrition conference at the Australian Institute of Sport in Canberra, researchers and coaches were buzzing about an emerging practice they refer to as “train low, compete high.” The idea is to do some of your workouts in a carbohydrate-depleted state – the nutritional equivalent of training while wearing a weighted vest – then race with a full tank of carbohydrates.

With initial research showing the technique boosts fat-burning, as well as other metabolic responses to exercise, elite athletes aren’t the only ones taking note. It remains a controversial approach – but it’s relatively easy to give it a try… [READ ON]

For more on this topic, including the idea that low-carb training might be suitable during base training but not other times of year, check out this blog entry from last month.