When you're afflicted, there's a time to keep going, a time to ease up, and a time to rest

By Tish Hamilton

Statistically speaking, we are all equal in the eyes of the flu god. Need historical proof? Cast your mind back to the 1976 Winter Olympics in Innsbruck, Austria: When an influenza outbreak ripped through the ranks of athletes, 25 were forced to take a powder. A tough strain of flu was also to blame for Atlanta Braves star pitcher Tom Glavine's bowing out of game one of the 1999 World Series, thus helping jump-start the Yankees' sweep. Granted, for the rest of us a bout of flu or even a nasty cold won't crush championship dreams, but it's a frustratingly frequent impediment to the pursuit of winter sports. According to a 1995 health survey conducted by the Centers for Disease Control and Prevention in Atlanta, 169 million cases of flu and cold were reported in the United States, the majority between October and April. Medical statisticians can't settle on an exact seasonal average per person—indeed, according to the Cleveland Clinic Foundation, by some estimates Americans suffer one billion colds in the course of a single year. The point, of course, is that if you're human, you will get sick. Which leads to a couple of vexing questions: When ill, should you work out? And if so, how hard and for how long?

First, a piece of good news: Exercise seems to reduce your chances of falling ill in the first place. Maybe they're just bragging, but athletes swear they get sick less. In a survey by the American College of Sports Medicine, 61 percent of 700 recreational runners said they'd had fewer colds since they began running; of the 170 runners who had been training for more than 10 years, more than 90 percent agreed with the statement that they "rarely got sick."

On the other hand, you are pushing your luck if you try to pull off heroic endurance feats every day. "When your immune system is under stress, you're more prone than usual to have viruses divide in your body," explains David Nieman, a professor of health and exercise science at Appalachian State University in Boone, North Carolina. In a study of 2,311 randomly selected finishers of the 1987 Los Angeles Marathon, Nieman found that 13 percent suffered upper respiratory infections the week following the race, compared with 2 percent of runners who did not run in the marathon. Nieman also found that runners who logged more than 60 miles a week were twice as likely to get sick than those who ran under 20 miles a week. The subtle message: Don't run yourself ragged.

What happens when you do come down with something, as you inevitably will? If you're a card-carrying member of the HMO masses, your primary care physician will probably give you a one-size-fits-all prescription to stop working out until you're symptom-free for over a week. A doctor who specializes in sports medicine, however, would give you an answer more tailored to your fitness level and whatever ails you. Lewis G. Maharam, president of the Greater New York Chapter of the American College of Sports Medicine and author of The Exercise High: How to Get It, How to Keep It, takes a philosophical approach to the physiological. "It really depends on what you're sick with," he says. "You don't have to take a day off unless you have a fever. Everything else you can do if you can do [it]." Which is the doc's way of saying, moderation is the key.

Photos: Craig Cameron Olsen; Insets, clockwise from bottom left: Dale Degabriele/Tony Stone Images; Peter Zeray/Photonica; Box Office/Photonica; Paul Vozdic/Photonica; Peter Zeray/Photonica