Exercise: Too Much of a Good Thing?
When it comes to exercise, I have the zealotry of the converted. As a kid, I faked asthma attacks to get out of the Presidential Physical Fitness Test, once missed my heat at a swim meet because I was in the locker room studying for a calculus test, and as a softball player, truly earned the nickname of Hardly Homerun Hobson. Then, in my early 20s, I discovered running, and soon you couldn't shut me up about the virtues of prolonged exercise. I started running marathons. When that got old, I took up triathlons and have now competed in several Ironman races. For years, I've insisted to everyone who questions whether 12 straight hours of exercise can possibly be good for me, that of course it is. How can it not be?
Except that sometimes, during the last 10K of a marathon, for instance, when I start bargaining with my quads like an atheist in a foxhole, I wonder whether that much e xercise can possibly be good. And a number of recent studies suggest that my exercise regimen could be doing damage to my heart, immune system, and the rest of my bod.
So I called Arthur Siegel, chief of internal medicine at the Harvard-affiliated McLean Hospital. For years, he has been studying nonelite Boston Marathon runners, and he runs the things, too, so I assumed he'd be a rabidly kindred spirit. He agrees that getting a moderate amount of exercise is one of the best things you can do for your health. Not so racing 26.2 miles. "Marathon running is an overdose of a good thing," he says.
That was not what I expected to hear. But Siegel has studied two phenomena that occur in marathonsnot commonly but enough to kill a handful of people every year. First is a heart attack. A few years ago, he tested 60 marathon runners before and after a race, looking at their heart rhythms and their blood for signs of damage that might indicate a heart attack. After the race, 40 percent showed enough evidence of blood markers to indicate heart damage, though the damage reversed itself within a few days. (The runners who trained the least had the most damage, suggesting proper conditioning is protective.)
Stressed out. The toll of running that long and that fast has a host of effects, including systemic inflammation and the promotion of blood clotting, both of which can lead to midrace heart attacks in people with some level of previously silent heart disease (and at a certain age, all of us probably have plaque in our vessels). "I'm not saying don't do it," he says. "It's a great way to expand your knowledge of yourself and test your limits. But if you're a middle-aged person at risk for coronary problems, you should probably do the training and skip the race."
Siegel has also studied hyponatremia, the potentially deadly condition that occurs when people in long endurance events (say marathoners who take more than four hours to finish or adventure racers) take in too much water or sports drinks. In its extreme cases, it can lead to brain swelling, seizures, and death.