How Much Is Too Much?
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 20s, I discovered running, and you couldn't shut me up about the virtues of exercise. I started doing marathons. When that got old, I took up triathlons and have now done several Ironman races. I insist, to everyone who asks whether 12 straight hours of exercise can possibly be good for me, that of course it is.
Except that sometimes, like during the last 10K of a marathon, when I start bargaining with my quads...I wonder if that much exercise can possibly be good for me. And a few studies I've seen, on what too much exercise might be doing to my heart, immune system, and the rest of my bod, had me wondering, too.
So I called Arthur Siegel, chief of internal medicine at the Harvard-affiliated McLean Hospital, who for years has studied nonelite Boston Marathon runners. Siegel runs the things, too, so I assumed he'd be a rabidly kindred spirit. And 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 said. That wasn't what I expected to hear. But Siegel has studied two phenomena that occur in marathons often enough to kill a handful of people every year. First is heart attack. A few years ago, he tested 60 marathon runners before and after the race, looking at their heart rhythms and their blood for signs of heart damage. After the race, 40 percent showed enough evidence to indicate damage, though that reversed within days. (The runners who trained the least had the most damage, suggesting proper conditioning is protective.)
Skip the race? The stress 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, we almost all have some 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 take in too much water or sports drink. I consoled myself with the fact that I am not a middle-aged man and that I've gotten the hang of balancing my fluid intake. Like other racers, though, in the week following a big race, I often come down with a bug. And last season, I seemed to have a chronic sore throat, mild fever, and fatigue. Not to mention chronically crummy race results.
None of this is uncommon, I learned. David Nieman, in the department of health and exercise science at Appalachian State University, years ago abandoned marathons for working on his farm (and says he feels much better now). He says that while immunity goes up when you work out moderately for about an hour, immune function decreases when you work out for more than 90 minutes (a reason marathon runners get sick after a race). The long-term effects of this immune system suppression aren't clear.
As for my fatigue last season, I was probably flirting with overtraining, I concluded after talking with Jack Raglin, who does research in kinesiology and sport psychology at Indiana University. This isn't the same as exercise addiction, where people take multiple classes a day at the gym and compulsively work out. Overtraining syndrome is defined by its symptoms: changes in mood, altered appetite and sleep patterns, perhaps a series of colds, and a decline in performance. It's common in endurance sports or other sports that require intense off-season conditioning. The only way to break the cycle, he says, is to rest. Which is what I did after my disappointing season.
After talking to all these experts, I'll concede that speaking purely of physical health, I long ago reached the point of diminishing returns from my workouts. "I tell everyone to walk vigorously 30 minutes a day," says Paul D. Thompson, a cardiologist at Hartford Hospital in Connecticut. Exercise does raise the odds of a heart attack while you're working out, but if you do it consistently, it cuts your chances of heart problems over the long term—and provides a host of other benefits, from staving off obesity to preventing osteoporosis and possibly cancer. Quadrupling or quintupling Thompson's prescription isn't going to similarly increase my chances of better health and, if I'm not careful, may put me at risk for other problems.
That said, there's no way I'm giving up my two-hour runs and six-hour bike rides. Some people climb mountains or meditate to achieve mental and emotional clarity or to cope with stress; I work out for a long time. Instead of drastically reducing my training, which would have the side effect of making me extremely unpleasant to be around, I've decided to make a concerted effort to maintain balance in my life: to occasionally sleep in rather than head to the pool at 6 a.m., to spend an hour with friends or family for every one I spend on my bike, and to generally put my training in the larger perspective of my life. While, of course, still trying to kick ass in my next race. That, I feel in my gut even if I can't prove it with research, is the best exercise routine for me.
This story appears in the June 25, 2007 print edition of U.S. News & World Report.