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Exercise May Reduce the Risk of Colds and Flu

Tribune Media Services

Things are heating up for those of us headed to the Winter Olympics in Vancouver. I am looking forward to being there as team physician for the U.S. Speedskating team.

In that role, I take care of team members' injuries and their basic medical needs. If an athlete is injured on the ice, I'll take care of that. Or if someone gets a cold, I'll take care of that, too.

When it comes to colds and flu, people often wonder how they can take better care of themselves, especially during particularly scary cold-and-flu seasons, such as this year's. Preventative hygiene is a good start. Another protective measure is moderate exercise.

Research shows that people who do moderate exercise most days are less likely to catch colds and the flu. According to a study published in the journal Medicine and Science in Sports and Exercise, active folks caught only one upper-respiratory tract infection a year on average, while less active folks averaged more than four.

The exercise you're doing now may also protect you next year. Another study, published in the American Journal of Medicine, noted that those who stick with a yearlong, moderate-intensity program may have an even greater reduction in the incidence of colds. And several studies suggest that if you do come down with the flu or a cold, having engaged in a regular exercise regimen can cut the duration of the illness in half.

There are several theories regarding how these illnesses are beaten back by time on the treadmill. One is that physical activity may cause the disease-fighting white blood cells in your body to move from your organs into your bloodstream, and that your increased heart rate may circulate antibodies and white blood cells through your body more quickly. It's thought that, by arriving more promptly on the scene of potential infection, these defense cells may pinpoint bacterial and viral intruders earlier and more effectively.

Another theory is that your increased circulation may trigger an early release of the hormones that sound the alarm summoning your body's other immune responses. Still another posits that the rise in body temperature as you exercise may act as something of an artificial "fever," which serves to inhibit the growth of bacteria and viruses. Others believe that exercise does a respiratory deep-cleaning, scrubbing bacteria that could cause colds and flu out of your lungs. Or that your increase in urine and sweat output may more efficiently flush disease-causing cells from your body. Still other evidence points to the ways in which exercise inhibits your body's stress response and thus lowers the impact disease-causing stress can have.

No matter the biological mechanisms at work, the key to experiencing fewer sniffles through exercise is moderation. Don't go overboard. A long-term program of intense exercise may increase stress hormones and can actually reduce the number of white blood cells circulating through your body. Thus, if you overdo exercise, you may actually increase your susceptibility to colds and flu.

I find that people who are training as hard as the folks I'll be taking care of at the Olympics, for example, often have compromised immune systems. To protect the athletes in Vancouver, I'll be preaching preventative hygiene: frequent hand-washing and the use of hand sanitizers. Meanwhile, everyone officially involved with the games is being vaccinated against H1N1 flu, most recently, more than 100 employees of the U.S. Olympic Committee.

There is no telling how the H1N1 flu will play out in the coming months and into next fall and winter, but I can offer some assurance that maintaining a steady program of moderate, regular exercise is a preventative measure everyone should take.

(Eric Heiden, M.D., a five-time Olympic gold medalist speed skater, is now an orthopedic surgeon in Utah. He co-authored "Faster, Better, Stronger: Your Fitness Bible" (HarperCollins) with exercise performance physician Max Testa, M.D., and DeAnne Musolf.

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