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Gym Flu

James Rouse's passion for endurance sports always paid huge health dividends. Then he extended his workout and was rewarded with fatigue, recurrent colds, slow recovery, irritability, anxiety and sleeplessness. "I remember feeling how unjust it was that I worked so hard and was getting so sick," says Rouse, 38, a naturopath in Denver, Colo.

Rouse didn't realize that his accelerated training schedule could compromise his immune system. Getting healthy was actually making him sick.

Break It Up
Overtraining and stress have long been known to compromise immune function. A 1987 landmark study of marathon runners found that they were six times more likely to get sick after completing a race than non-runners. But exactly how much exercise is bad for you?

"When you push the pace for 90 minutes or more, that's when the immune system begins to wear down," says exercise scientist David Nieman. "That translates to any high-endurance activity, including cycling, rowing and tennis."

The culprit is the hormone cortisol, which floods your insides during bouts of physical and emotional stress. Immune cells in a dozen parts of the body begin to fray; they can remain in their fragile condition for as little as three hours or as much as three days. Along with making you feel tired and grouchy, such stress can cause an increased morning heartbeat, something that those favoring pre-work workouts should keep in mind.

You can fudge the 90-minute figure by breaking up your workout. Nieman studied Olympic athletes who did just that. "They train up to three hours a day, but their infection rates are not high," says Nieman. "They also manage stress well, get enough sleep, and maintain an excellent diet." He suggests a "health zone" of optimal activity from 30 to 60 minutes.

If you've only got one training slot per day, try substituting low-impact activities now and then, especially if you're feeling off. You can also incorporate stretching throughout your workout, not just before and after, and remember to take minibreaks during long cardio sessions.



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