Too Much Exercise Can Make You Sick

Question: For six months, I’ve been running 5 miles three times a week and cycling one hour two times a week. I’ve reached my goal (losing 10 pounds), but now I’m getting sick all the time. Is there an exercise/cold connection?


Monterey, Calif.

Answer: There may be a connection, but only with too much exercise, researchers say. New studies by David Nieman, a professor of health and exercise science at Appalachian State University in Boone, N.C., has revealed, for example, that marathoners’ immune systems drop sharply for three to 72 hours after their events. The reason is simple--extreme exercise releases a flood of stress hormones, which can create an open window for germs and other nasties to gain a foothold.


Other research, from the Cooper Clinic in Dallas, has found that heavy physical training every day --with no significant periods of rest--is linked to the chronic suppression of white blood cells called neutrophils. Neutrophils are an important part of the immune system’s first line of defense.

To avoid weakening your resistance to colds and other illnesses, vary your workouts and training intensity. Add easy or shorter workouts to your regimen, and try cross training, yoga and resistance training for variety. Additionally, be sure to get plenty of sleep and nutritional sustenance to boost your immune system.


Stephanie Oakes is the fitness correspondent for Discovery Health Channel and a health/fitness consultant. Send questions by e-mail to: She cannot respond to every query.