According to the American College of Sports Medicine, cold sufferers who engage in moderate exercise experience less severe cold symptoms and get over their colds faster than their sedentary counterparts.

Those who engage in regular exercise tend to catch fewer colds. In fact, a series of studies in the '90s found that moderate exercise reduces the duration of the common cold by 50%.

Not everyone who has a cold should exercise, though.

Medical professionals use a rule of thumb known as the "neck rule." If your cold symptoms are above your neck--stuffy nose, sneezing, sore throat, headache--you should be okay to exercise. But if you're running a fever or feel congestion in your chest, you should skip the treadmill and stay in bed.

If you do decide to exercise while fighting a cold, moderation is the key. Strenuous exercise can actually weaken your body's immune system, keeping you sick longer.

For tips to avoid getting sick, check out InsWeb.com's Staying Healthy This Flu Season.