May 26, 2013 9:51 PM GMT
Also a bit about "over hydrating" that can be fatal... hmmm...
Other recent studies suggest the significant mortality benefits of running may diminish or disappear at mileage exceeding 30 miles a week and other, very small studies have shown elevated levels of coronary plaque in serial marathoners—a problem that rigorous exercise theoretically could cause.
"Heart disease comes from inflammation and if you're constantly, chronically inflaming yourself, never letting your body heal, why wouldn't there be a relationship between over exercise and heart disease?" said John Mandrola, a cardiac electrophysiologist and columnist for TheHeart.org.
Yet sports-medicine specialists are sharply divided over whether any warning is warranted. For every American who exercises to extremes, after all, there are thousands who don't exercise at all—and who might embrace any exercise-related warnings as cause for staying sedentary. Moreover, the evidence for extreme-exercise hazards is far from conclusive—and is contradicted by other studies suggesting the health benefits of exercise may accrue to infinity.
"It's true that the majority of cardiovascular protection comes from exercise at more moderate levels, but there is compelling evidence that there's no upper limit," said Benjamin Levine, director of the Institute for Exercise and Environmental Medicine in Dallas and professor of medicine at the University of Texas Southwestern Medical Center.
"I don't want anyone to read that exercise can be bad for you. added Mandrola, a passionate cyclist. "Some folks do tons of exercise and are protected. Some folks probably have some individual susceptibility to it. I'm a big believer in short intervals of high intensity."
Sports medicine has a history of ignoring warning signs. Long after evidence emerged that over-hydrating could prove fatal to marathoners, experts continued encouraging runners to drink as much as possible—leading to utterly preventable tragedies such as the death of a 43-year-old mother of three in the 1998 Chicago Marathon. "Why did it take 20 years before the original evidence was accepted?" asked a 2006 article in the British Journal of Sports Medicine.