Cardiologist James O’Keefe fears that endurance athletes are killing themselves by overtraining. Erin Beresini presents both sides:
"Marathoners and Tour de France cyclists have incredibly fit cardiovascular systems," O’Keefe says. "But it’s not an exercise pattern one should sustain for decades. It demands so much from the heart that you literally accelerate the aging process."
O’Keefe’s findings grabbed headlines—and forced a good number of the estimated 15 million Americans who participate in endurance sports to reconsider their training regimens. Other experts, however, think O’Keefe’s warnings are overblown. "The idea that ultra activities put people at acute risk of sudden cardiac death is warmongering," says Keith George, head of the Research Institute for Sport and Exercise Sciences at England’s Liverpool John Moores University. "It’s not supported by the evidence."