People who exercise report fewer colds than people who don’t.
Two studies on women were carried out. The exercise group walked briskly for 35-45 minutes, 5 days a week for 12-15 weeks. The control group stayed inactive. The exercise group experienced about half the days with cold symptoms as the inactive group.
During moderate exercise, the immune system experiences positive changes. The pre-exercise levels return very quickly once the session finishes, but it does give you a ‘boost’ that seems to reduce the long term risk of infection.
So, does more exercise mean you get a bigger ‘boost’?
As with most things there is an optimum. After prolonged exercise (eg marathon running) people experience a steep drop in their immune function which lasts at least 6-9 hours. Does this mean you shouldn’t do more exercise? No, just be aware so give your body a rest if it needs it.
So should I exercise when I am ill?
If in doubt, ask your doctor! The general rule of thumb, is if you have a cold and your symptoms are above the neck then mild to moderate exercise is ok if you want to participate. With anything else, take a break, rest and recover. As with everything, listen to your body.