Author: alex

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When one twin runs more than the other

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My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

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Interesting new study from Paul Williams’ National Runners’ Health Study — no, wait, this is a new one, not the one I wrote about a few days ago! This one looks at identical twins to find out the extent to which your body shape is dictated by your genes. Yes, the old nature vs. nurture debate…

Williams has an enormous data set of over 100,000 runners, including 926 identical twins. He explored the relationship between two quantities: the difference in how much a pair of twins ran, and the difference between how much they weighed. Various studies have found that genetic factors account for 40% to 70% of the variation in BMI. But Williams found that the more the active twin exercised, the less genetics seemed to matter. Here’s a graph:

The numbers on the right-hand side represent how much more the active twin runs than the less-active twin. Of course, for some people the results will seem absurdly obvious: the greater the difference in activity levels between two people, the greater the difference in their BMI. Still, it’s a good reminder that genetics isn’t destiny. Here’s what Williams concludes:

Extrapolating the coefficients of Table 3 shows that BMI inheritance might be eliminated completely by running 7.05 km/day (23 mi/wk) in women and 13.51 km/d (60 mi/wk) in men, a projection that is consistent with our previous finding of uncorrelated BMI values in 35 pairs of MZ twins whose running differed by an average of 8 km/d [31], but a projection that should nevertheless be considered with caution.

 

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Burfoot, Noakes, and the ultimate workout

THANK YOU FOR VISITING SWEATSCIENCE.COM!

My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

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Fascinating post on Amby Burfoot’s Peak Performance blog about a recent Yale study on the mind and appetite hormones. Researchers gave subjects either a high-calorie or a low-calorie milkshake (and told them which one they were getting), then measured the change in ghrelin, a key appetite hormone:

As you would expect, the subjects’ ghrelin levels dropped after the indulgent, high-calorie shake. After all, this thing contained more than 600 calories. It would fill up anyone. When the subjects drank the low-cal shake, their ghrelin levels stayed basically the same.

Here comes the twist: The shakes were identical; they were all moderate-calorie.

So what does this mean? Amby goes on to discuss other phenomena like “sham arthroscopy” and the”world’s best running workout.” The whole post is worth a read, but I found his suggestion for a workout particularly interesting: 5 x 1 mile as hard as possible… then when you’re done, your coach makes you do one more at the same pace:

From this workout, you’ll learn forever that you’re capable of much more than you think. It’s the most powerful lesson you can possibly learn in running.

I agree. And it also made me think of something Tim Noakes told me when I interviewed him last summer. I’d asked about the origins of his “central governor” model, and how coaches might actually apply its lessons in practice. Here’s what he said:

I think all the great coaches always work on the brain anyway. And they get you to run faster because they teach you that you can… I remember the compelling moment in my own rowing career was we used to do 6 times 500 metre repetitions. And one afternoon, we did our sixth and turned around rowing back to the boathouse, and the coach says, ‘No, go to the start again. You’re doing another one.’ So we did another 500. And he said go back. And we did another four. And you know, no one would have believed that we could do that, if you’d asked us… That taught us that you have to teach athletes, somewhere in their careers, that they can do more than they think they can.

As Amby points out, the problem is that you can’t prescribe a workout like that to yourself: you need a trusted authority telling you what to do. This is a really interesting and important point. We keep on discovering that the brain is more powerful than we’d suspected in regulating performance (and even appetite hormones) — but it’s still not clear how we can actually harness these powers.

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The more you exercise, the less diet matters

THANK YOU FOR VISITING SWEATSCIENCE.COM!

My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

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This week’s Jockology column in the Globe and Mail takes a closer look at some new results (which I blogged about back in April) from the long-running National Runners’ Health Study:

At a public debate in May on the relative importance of exercise and diet in battling obesity, Yoni Freedhoff began his opening arguments with some basic physics.

“There’s no debate about whether the laws of thermodynamics exist,” said Dr. Freedhoff, the medical director of the Bariatric Medical Institute in Ottawa. Energy can’t be created or destroyed, so weight loss ultimately depends on burning more calories than you consume. But which side of that equation should you focus on? [READ THE FULL ARTICLE]

The basic finding of the new study is that the more you exercise, the weaker the link between diet and weight. I exchanged a few e-mails with Yoni Freedhoff (of Weighty Matters fame) about this idea, and his initial reaction was that the findings could be interpreted as simply the result of calories burned while running. After all, running 8 km per day (as the “top” group in the analysis does) burns quite a few calories. I tend to think that there’s more going on here (as I explain in the article), but I’d certainly be interested in hearing what others think. Am I making too big a deal about something that’s completely obvious?

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Vigorous exercise prevents “silent strokes” in older adults

THANK YOU FOR VISITING SWEATSCIENCE.COM!

My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

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Just noticed a press release about a study on exercise and brains in older people, reaffirming the well-established idea that there are benefits to more vigorous exercise that you can’t get from mild exercise:

Older people who regularly exercise at a moderate to intense level may be less likely to develop the small brain lesions, sometimes referred to as “silent strokes,” that are the first sign of cerebrovascular disease…”These ‘silent strokes’ are more significant than the name implies, because they have been associated with an increased risk of falls and impaired mobility, memory problems and even dementia, as well as stroke,” said study author Joshua Z. Willey, MD, MS, of Columbia University…

The study involved 1,238 people who had never had a stroke. Participants completed a questionnaire about how often and how intensely they exercised at the beginning of the study and then had MRI scans of their brains an average of six years later, when they were an average of 70 years old.

You can read the press release for more details, but the basic gist is: these lesions are not uncommon (16 percent of participants had them), and those who did moderate to intense exercise were 40 percent less likely to have them than those who did light exercise or no exercise, while controlling for other risk factors like blood pressure, cholesterol and smoking. Just another data point to bear in mind!

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Feeling healthy v. objective fitness

THANK YOU FOR VISITING SWEATSCIENCE.COM!

My new Sweat Science columns are being published at www.outsideonline.com/sweatscience. Also check out my new book, THE EXPLORER'S GENE: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map, published in March 2025.

- Alex Hutchinson (@sweatscience)

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Which is more important: feeling healthy, or being fit? That’s the question addressed by a new British Journal of Sports Medicine study from Steven Blair’s group at the University of South Carolina. Blair is best known for pioneering the research that suggests that fitness is more important than fatness as a predictor of health outcomes. In this case, he and his colleagues take a look at “self-rated health” (SRH), which has been touted lately as a valuable health-assessment tool.

SRH is assessed by simply asking:

How would you rate your overall health?

The answers are poor, fair, good or excellent. The researchers compared the predictive values of SRH to aerobic fitness, assessed using a maximal treadmill test (with the modified Balke protocol, which is apparently highly correlated to VO2max). The study followed 18,488 men who were tested between 1987 and 2003, 262 of whom died during the 17-year follow-up period. They controlled for age, BMI, physical activity, smoking, alcohol, heart disease, diabetes, cancer, and several other confounders.

Not surprisingly, being fit and having a high SRH reduced your chance of death dramatically. The real question is what happens when you separate the two factors. Aerobic fitness was strongly protective against mortality even when all other factors were controlled. SRH and mortality were were still inversely correlated, but the association was “only marginally significant (p=0.09)” once aerobic fitness was controlled for.

Given the previous research topics of this group, I suspect they set out to show that all the apparent predictive power of SRH is just a byproduct of aerobic fitness. It seems safe to conclude that fitness is indeed the more important of the two, but it’s interesting that SRH retained some predictive power. Their thoughts on why this might be:

One plausible explanation is the afferent information that conveys messages from the organism to the brain. These messages are usually not brought to consciousness because they function at lower levels of the central nervous system. However, this afferent information is perceived by the individual as sensations, feelings and emotion and is the sense that reflects the physiological condition of the entire body. Another theory explaining a person’s perceptions of their health involves a family of proteins called cytokines. Cytokines are involved in inflammation processes and play a major role in infectious conditions and also the pathogenesis of many chronic diseases. Research is beginning to show that the inflammatory process and certain cytokines are associated with tiredness, impaired sleep, depressive mood and poor appetite.

On one level, this seems a bit needlessly complicated. After all, most of us can probably make a reasonable assessment of how healthy we are without relying on unconscious afferent feedback and cytokines! Still, the idea that our “sensations, feelings and emotion” can reflect our underlying health status is also interesting — and inarguable. After a few late nights, skipped workouts and junk-food binges, we tend to feel like crap. This isn’t just guilt and fatigue: it’s the body sending a distress signal.