Friday, November 30, 2012

Risks of an overdose are greatly exaggerated.

      In this case, it should sound extra-familiar, because the Heart editorial is co-written by some of the same team that wrote "Cardiovascular damage resulting from chronic excessive endurance exercise" in July, and "Potential adverse cardiovascular effects from excessive endurance exercise" in June, not to mention last year's "Exercise like a hunter-gatherer: a prescription for organic physical fitness." As cardiologist Paul Thompson says in the WSJ piece, "The guys advancing the hypothesis that you can get too much exercise are manipulating the data... They have an agenda."
     Of course, I have an agenda too. I like running, and that inevitably colors my perspective. I posted my thoughts on this topic in a detail earlier this year, during one of the earlier iterations of this same debate (sparked by essentially the same article by James O'Keefe et al. in a different journal). As I said then, there's no doubt whatsoever that the health benefits of aerobic exercise eventually reach a point of diminishing returns. Where is that point? No one really knows, but my personal feeling is that if you're running more than an hour a day, you're doing it for reasons other than optimizing health. Which is fine. But crucially, that doesn't mean you're hurting your health by running an hour a day, and when people start making suggestions like that, I agree with Thompson that they're twisting the data. Two examples:
     (1) One of the major pieces of evidence the group cites is a study that was presented at a conference over the summer. The WSJ description:
In a study involving 52,600 people followed for three decades, the runners in the group had a 19% lower death rate than nonrunners, according to the Heart editorial. But among the running cohort, those who ran a lot—more than 20 to 25 miles a week—lost that mortality advantage.

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