What impact does exercise have on the immune system? According to a study conducted by David Nieman, PhD, professor of health and exercise science and director of the Human Performance Lab at Appalachian State University, positive immune changes occur during moderate physical activity. Consistent physical activity (30 minutes of physical activity almost daily) helps improve the immune system and may lead to fewer sick days from the common cold and other upper-respiratory tract infections (URTI). However, risk of URTI can actually increase when athletes push themselves beyond normal limits. The immune system exhibits adverse change after prolonged, heavy exertion lasting longer than 90 minutes. The state of impaired immunity may last between three and 72 hours, during which time bacteria and viruses can gain a foothold. The risk of infection increases when other immunity-impairing factors—such as lack of sleep, severe mental stress, malnutrition and weight loss—are present.
To counter the increased risks of URTI, athletes should aim to adhere to these guidelines:
- Keep other life stresses to a minimum.
- Keep vitamin and mineral stores at optimal levels.
- Avoid overtraining and chronic fatigue.
- Get adequate sleep on a regular basis.
- Avoid rapid weight loss.
- Avoid touching the eyes and nose with hands.
- Avoid sick people and large crowds when possible.
- Get a flu shot during winter months.
Nieman also addressed a question many fitness professionals and athletes ask: Should I exercise when sick? In general, if the symptoms are from the neck up (e.g., the common cold), moderate exercise is probably acceptable and perhaps even beneficial. If the illness is systemic (such as the flu), bed rest and a gradual progression to normal training levels are recommended. Consult your doctor if in doubt. (Source: Georgia Tech Sports Medicine & Performance Newsletter, October 2001.)