Can Extreme Endurance Exercise Kill?

Exhausted runner wall teaser

No matter how fast you run, you can’t escape the debate over the dangers of extreme endurance exercise.

In July, a group of researchers lobbed the first round, in a review published in Mayo Clinic Proceedings—as you exercise longer and harder, they said, not only do the benefits drop off, but extreme workouts damage your heart.

Following up in an editorial published in the journal Heart, the same authors, who are cardiologists, emphasize that moderate endurance exercise provides the most benefits—that is, you’ll be better off down the road if you don’t run too far or too hard.

“Yeah, right,” you say, with your eyebrows raised and one running shoe already out the door. Doubt is good, but here’s the researchers’ evidence:

  • A 2012 study found that runners were 19 percent less likely to die than non-runners. However, the benefits of exercise decreased for runners who logged more than 20 miles a week.
  • Running faster than 8 miles per hour—or for longer than 1 hour—doesn’t give you any additional health benefits.

Is it time to hang up your ultramarathon shoes? Not quite yet.

Critics, like Paul Thompson, a former elite marathoner and a sports cardiologist, claim the authors have an agenda. “The guys advancing the hypothesis that you can get too much exercise are manipulating the data,” he told the Wall Street Journal.

In addition, a previous study in the Lancet showed that the benefits of exercise increase up to 120 minutes for moderate exercise and 60 minutes for vigorous exercise. After that, it plateaus, meaning—you don’t gain more, but you certainly don’t lose.

It will be some time before the war ends between the marathoners and the joggers. Until then, keep exercising; some is better than none. And if extreme is your thing, train smart, and see your doctor regularly to make sure your workouts are still helping.

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