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Archive for January, 2012

The incredible unaging triathlete

January 14th, 2012

Here’s a pretty graphic illustration, from a recent paper by Dr. Vonda Wright and her colleagues (hat tip to Laura McIntyre for the forward), of the importance of lifelong physical activity:

It’s from a new study freely available at The Physician and Sportsmedicine that took detailed measurements of 40 masters athletes between the ages of 40 and 81, and found a surprising lack of age-related muscle loss:

This study contradicts the common observation that muscle mass and strength decline as a function of aging alone. Instead, these declines may signal the effect of chronic disuse rather than muscle aging.

 

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Marathon heart attacks: new data

January 13th, 2012

There’s a big new study out in the New England Journal of Medicine that takes a comprehensive look at every case of cardiac arrest during every marathon or half-marathon in the U.S. with more than 100 participants between 2000 and 2010. It’s being widely covered in the press; you can read a good summary in the New York Times or in the Globe and Mail, among other places. The primary message: these events are rare. There 59 cases of cardiac arrest, of which 42 were fatal. That translates to a 1 in 259,000 chance of dying, which is much lower than previous reports and than many other sports.

I’m actually in Houston right now for the U.S. Olympic Marathon Trials, and it happens that Aaron Baggish of Mass General, the senior author of the study, was giving a talk this morning to the members of the World Road Race Medical Society — so I popped in to hear what he had to say. A couple points he made that I found interesting:

Weather wasn’t a factor. The average starting temperature during events where someone suffered a heart attack was almost identical to the 10-year average (55.9 vs. 55.5 F), and the average deviation was just 0.3 degrees.

For 31 of the cases, they were able to track down either the survivor or the next-of-kin and get full medical records, autopsy results, and running history — so this allowed them to really look at the causes of death in detail. One of the surprises is that none of the runners died from a ruptured plaque producing a blood clot, which is (or at least was) thought to be one of the possible mechanisms of sudden death in athletes. The problem with ruptured plaques is that they’re hard to predict in advance. But if underlying coronary artery disease is the real problem (more on that in a sec), then pre-exercise cardiac screening should be able to pick some of that up, Baggish argues.

The average age of the people who survived cardiac events was 53; the average age of the people who died was 34. There are two distinct groups here. One is young people with thick hearts (“hypertrophic cardiomyopathy”), an underlying genetic conditionl; when they collapse, they’re very hard to revive and tend to die. The other is older men with narrowed arteries (coronary artery disease) due to the usual risk factors; when they collapse, they can often be revived if someone gets to them soon enough.

That brings me to one of Baggish’s key point: the absolute best predictor of whether someone would survive cardiac arrest during a race was simple: did a bystander start CPR immediately, before paramedics got there? The lesson is simple: we should all — runners, family members, spectators, heck, everyone in society — have basic CPR training. It could make all the difference to someone, including you.

Baggish’s overall message: running (and by extension, other aerobic activity) is generally safe — but it doesn’t give you immunity from heart disease. That means that everyone, and particularly older males, should be alert for warning signs and not ignore them. Some key ones:

  • a burning sensation in the chest (could be confused with acid reflux) that comes on when you start running then gradually fades away, and keeps recurring;
  • breathing more heavily than you’d expect given your effort;
  • persistent, unusual fatigue.

None of these risk factors necessarily mean something is wrong, but they can be a signal that it’s worth checking in with your doctor to see is you’ve got coronary artery disease that needs to be addressed before racing a marathon.

Last point. Previous studies have shown that most marathon race deaths occur in the final mile or at the finish; this study confirms that. The implication: if you have reason to worry about your heart’s health and want to minimize that risk, think twice about your final sprint. Here’s the data, broken down by race quartile:

The more you eat, the faster you go (in ultraendurance)

January 10th, 2012

A few months ago, I blogged about a study that observed correlation between in-race carb intake and race time in Ironman triathletes. What was significant about that paper is that it looked at a topic that has been studied to death in the lab, and took it out into the real world. There are a lot of “problems” with the real world that make it hard to nail down causes and effects — but ultimately, the whole point of this type of research is to understand what’s happening in the real world. So these observational studies, despite their challenges, are very important.

That’s by way of intro for another small study, just published in the International Journal of Sport Nutrition and Exercise Metabolism, from researchers in New Zealand. They looked at the nutritional intake of participants in a brutal cycling race, the K4, which covers 384K and includes 4,600 metres of climbing. The average finishing time of the 18 study participants was 16 hours and 21 minutes! The key points:

  • The estimated calorie burn for the race was about 6,000 calories; the average intake was just 4,500 calories, so there was a big caloric deficit.
  • There was a significant inverse relationship (p=0.023) between number of calories consumed and finishing time. The more calories you managed to cram down your gullet, the faster you finished!

Is this a surprise? Given that the race was so long, it makes sense that taking in enough energy was a significant challenge. Obviously the same thing doesn’t apply during, say, a 100-metre sprint. The question is: where’s the breakpoint, beyond which energy intake becomes a significant independent predictor of performance? I think the general assumption is that it’s probably a bit below marathon distance — so it would be really interesting to see a study like this, with a very large number of participants, at a marathon.

Five tips for cold-weather workouts

January 9th, 2012

My Jockology column in today’s Globe and Mail gets seasonal and looks at five bits of research related to exercising outdoors in the winter. For example:

The challenge: Going bareheaded in the winter is like leaving the lid off your thermos. Classic studies in the 1950s showed that if you wear winter clothes but no hat at 4 C, you lose about 50 per cent of your body heat through your head.

The research: A U.S. Army study published in early 2011 showed that your face is almost as important as the top of your head for heat loss. Volunteers spent an hour in a cold chamber with a wind chill of -20 C; those who wore a balaclava had measurably warmer fingers and toes than those wearing a normal hat. Your body tries valiantly to keep your brain warm by shunting blood away from your extremities toward your head.

Read the whole column here.

Maternal exercise lowers fetal heart rate

January 7th, 2012

A new study in Medicine & Science in Sports & Exercise, from the same group in Kansas City that previously found lower fetal heart rates when mothers exercised during pregnancy. This time, they were looking for a dose-response effect — the more exercise, the lower the heart rate — which would strengthen the case for causality rather than correlation. Here’s what they found:

“A” is “active” and “Q” is “quiet (as in whether the fetus is moving around or lying still). The Q results weren’t statistically significant, but for the A results, greater intensity did indeed lead to lower heart rates. But perhaps most significant is what they didn’t find:

Interestingly, maternal factors (i.e. maternal age, maternal resting HR, maternal weight gain, pre-pregnant BMI) did not influence the associations between physical activity and fetal parameters. Fetal cardiac autonomic control was enhanced in mothers who participated in physical activity regardless of the amount of weight they gained, their weight status prior to pregnancy, resting HR or age.

In other words, they’re not saying that fit mothers have fit babies; they’re saying that active mothers have fit babies.

Lieberman on foot strike and injuries on Harvard’s XC team

January 5th, 2012

Does how you run cause (or prevent) injuries? Everyone has a theory, but no one has much data. Into the breach steps Dan Lieberman, with a new Vibram-funded study of injury rates on Harvard’s cross-country team between 2006 and 2011, just published online at Medicine & Science in Sports & Exercise. He looks at 52 runners — 36 rearfoot strikers and 16 forefoot strikers — all of whom recorded their daily training on an online running log during the study, and whose injuries were precisely recorded by the team’s trainers.

The results?

Approximately 74% of runners experienced a moderate or severe injury each year, but those who habitually rearfoot strike had approximately twice the rate of repetitive stress injuries than individuals who habitually forefoot strike.

Now, this is a very interesting and significant result. It also has limitations, which the authors take great pains to detail in their discussion. Probably the most important: this is a retrospective, non-randomized study. That means, for example, that it doesn’t address what happens if a habitual, lifelong rearfoot striker switches to a forefoot strike, which requires stronger calf and foot muscles.

Another point that the authors make is the presence of considerable individual variation. Here’s some of the data:

(The caption reads “Repetitive injuries/10,000 miles; moderate and severe.” Not sure why Harvard is apparently using a Commodore 64 hooked up to a dot-matrix printer to generate its graphics!) Anyway, the point is that some people seem to do just fine with their rearfoot strike, while others are frequently injured with their forefoot strike:

[M]any runners who [rearfoot strike] in shoes do not get injured or get injured rarely even when they train at high intensity. We predict that these runners have better form than those who do get injured: they probably land with less overstride and more compliant limbs that generate less severe impact loading and generate less extreme joint moments… These predictions are supported by several recent studies, and they emphasize the hypothesis that running style is probably a more important determinant of injury than footwear (with the caveat that footwear probably influences one’s running style).

So there you have it. The study’s not perfect, and it doesn’t settle these debates once and for all. But it takes us closer by offering some straightforward data — and that’s how science should work.

Meb in Skechers vs. Meb in Nikes

January 4th, 2012

Meb Keflezighi is an Olympic medallist and a New York Marathon champ. So when he signed with Skechers last summer, observers were… surprised. The company’s new “Go-Run” line promises to make you switch to a mid-foot strike: “The Way You’re Supposed to Run.”

So does it work?

Krista Austin, an exercise physiologist and longtime friend of Meb’s (read about her role in “rebuilding Meb” before his 2009 New York win here), points out this opportunity to compare strides. Here’s Meb in Nikes:

And here’s Meb in Skechers:

Can you see a difference? Any improvement?

The “Fat Trap” and biological determinism

January 3rd, 2012

I’ve received a few e-mails asking what I thought of Tara Parker-Pope’s recent New York Times Magazine piece (“The Fat Trap”), which talks about how the body fights off your attempts to make it lose weight. In general, I thought it was a good piece. The basic message I came away with is the same one I hear from people like Yoni Freedhoff: if you want to lose weight — and keep it off — you have to do so using an approach that you’re prepared to maintain for the rest of your life. You can’t go on a diet for six months, lose weight, and then resume your previous diet and lifestyle (or even go halfway back to your previous diet and lifestyle!). Many (perhaps even most) people who are trying to lose weight still see it as a temporary transitional stage. That’s not how the body works, and the more widely that message is spread, the better.

Having said that, a quick note about the apparent “biological determinism” that opposes weight loss. Parker-Pope discusses some of the research by Rupert Leibel’s group at Columbia University, in which subjects are placed on carefully controlled liquid diets to make them gain or lose weight in order to observe what changes take place in their metabolism:

The research shows that the changes that occur after weight loss translate to a huge caloric disadvantage of about 250 to 400 calories… Muscle biopsies taken before, during and after weight loss show that once a person drops weight, their muscle fibers undergo a transformation, making them more like highly efficient “slow twitch” muscle fibers. A result is that after losing weight, your muscles burn 20 to 25 percent fewer calories during everyday activity and moderate aerobic exercise than those of a person who is naturally at the same weight.

I also discuss this research in (plug alert!) my book, Cardio or Weights. And the part Parker-Pope doesn’t mention is that, when you feed people extra calories, exactly the opposite adaptation takes place. In other words, after gaining weight, your muscles burn about 15 percent MORE calories during everyday activity and moderate aerobic exercise. Parker-Pope presents the research as a part of the explanation for why it’s near-impossible to lose weight — but looking at the whole picture, that would mean that it should be impossible to gain weight in the first place! Sure, the barrier is a little bigger when you’re trying to lose weight (20-25% vs. 15%). But the point is, these changes in metabolic efficiency aren’t insurmountable barriers — otherwise no one would ever change weight at all.

Training one limb to strengthen the other

January 2nd, 2012

An interesting figure from a new Australian study in the European Journal of Applied Physiology:

The subjects in the study did eight weeks of heavy weight training — using only one leg (their dominant one). As you can see, they dramatically increased strength in both legs. This effect is well known, but I still think it’s pretty cool! The goal of this particular study was to try to figure exactly how this happens, using magnetic pulses to the brain to help assess the role of the nervous system. They did indeed find a significant reduction in “corticospinal inhibition” in both legs, suggesting that the training improves the transmission of the signal from the brain to the muscle, and this improvement applies to both sides of the body.

The point? Well, as the researchers note, it’s something to bear in mind if you have an injury in one leg or one arm. You might be able to keep the injured limb strong without even exercising it. Of course, you have to balance that against the risk of creating physical imbalances. I guess the ideal would be to train enough to increase strength without actually putting on muscle. As the researchers conclude, clinical trials of this approach are needed.

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