Exercise Needn't Make You Sick, but Listen to Your Body

Does exercise increase the chance of getting sick? It seems that, whenever I ramp up my exercise program, I get colds and sinus infections more often. I was wondering if you could shed some light on this.
-Babette, Palm Springs

The answer seems to depend on how hard, how intensely and how often you work out.

Research shows that positive changes occur in the immune system during moderate exercise. Immune cells appear to circulate through the body more quickly, and there may even be a temporary boost in the production of macrophages, which are cells that attack bacteria.

Such changes probably last only a few hours after a workout, but many experts believe there is a cumulative benefit for those who exercise moderately on a regular basis. People who work out routinely likely use fewer sick days than do those who don't exercise at all, they contend.

But there is also evidence that too much exercise, or extremely intense exercise, can reduce immunity. This is important for people who push themselves intensely when they work out and for those who train and compete in long events, such as marathons.

This doesn't mean you'll get sick more often if you train hard. It does suggest that, to reduce the risk of illness, intense or longer workout days be followed with rest or with less-intense training days to give your body a break.

If you become sick, your workout sessions need to be managed even more carefully. When you're ill, the body's immune system is already taxed -- and the stress of exercise might make it more difficult for you to get well.

Research in this area is not conclusive, but most experts agree that participation in light exercise, such as walking, is fine if your symptoms are primarily above the neck and you don't have a fever. However, if you have a fever or muscle aches or if you're extremely tired, it's probably best not to exercise until the symptoms pass.

To reduce the risk of illness while following a regular exercise plan:

Get plenty of sleep: Adequate rest helps your body recover.

Stay hydrated: Drink plenty of fluids before, during and after exercise.

Eat well (of course): Opt for a diet loaded with fruits and vegetables.

Jay Blahnik, a Laguna Beach-based personal trainer and IDEA Health & Fitness Assn. spokesman, can be reached at jay@jayblahnik.com or health@latimes.com.