Although there is evidence that regular exercise benefits the immune system, even fitness enthusiasts eventually come down with something.

If you happen to catch a bug, how do you decide whether it’s best to get some activity or get some rest? You can base it on your symptoms.

If it’s a common cold with a runny nose, sore throat and minor aches and pains with no fever, it is probably safe to engage in some moderate exercise and may even make you feel better. If you have a fever, aches and pains, swollen lymph nodes, chest congestion and stomach or intestinal issues, it’s best to get some rest and gradually ease back into your normal workout routine.

Does exercise really boost the immune system? To test this, the American College of Sports Medicine conducted two studies with young and elderly women to determine whether exercisers get fewer colds than non-exercisers.

In both studies, women in the exercise groups walked briskly 35 to 45 minutes, five days a week, for 12 to 15 weeks, while the control groups remained physically inactive. The walkers experienced about half the days with cold symptoms as the sedentary group.

Other research has shown that during moderate exercise, several positive changes occur in the immune system. Although the immune system returns to pre-exercise levels very quickly after the exercise session is over, each session represents a boost that appears to reduce the risk of infection over the long term.

Some cold and flu germs can live on hard surfaces for up to 48 hours, but the most common way they are transferred is through contact with an infected person. Wearing a mask when you must be in crowded or enclosed places can help prevent you from becoming infected.

Also, remember to wash your hands frequently with soap and water or with an alcohol-based sanitizer. Avoid rubbing your eyes and nose or biting your nails. And, most importantly, get a flu vaccine every year.

To lessen your chances of getting sick in the future and to improve your outcomes if it happens, stick to your exercise routine, eat a well-balanced diet, and get enough sleep.

You should also avoid overdoing it. While regular, moderate exercise is beneficial, too much exercise and being chronically fatigued can make you more susceptible to illness.

• Sherry DeWalt is the healthy lifestyles coordinator for the CGH Health Foundation in Sterling.