The Neck Check

Whether or not you should cancel your workout routine depends a lot on the type of symptoms you have. Most experts advise that you analyze where your symptoms primarily occur -- a process known as the “neck check.”

“A neck check is a way to determine your level of activity during a respiratory illness,” says Dr. Neil Schachter, MD, medical director of respiratory care at Mount Sinai Medical Center in New York. “If your symptoms are above the neck, including a sore throat, nasal congestion, sneezing and tearing eyes, then it's OK to exercise," he says. "If your symptoms are below the neck, such as coughing, body aches, fever, and fatigue, then it's time to hang up the running shoes until these symptoms subside.”

Moderation Is Key, Say Some

Some physicians believe exercising when sick is OK in moderation. Dr. Peter Katona, an associate professor of medicine at UCLA who specializes in infectious disease, isn't completely anti-exercise for fitness fanatics who’ve come down with a virus. However, he cautions them to listen to their bodies.

"If you feel up to it, you can do some light working out, like stretching," he tells the LA Times. "Do things that aren't going to give you a lot of sweat and fatigue. Don't push yourself, but let your body be your guide." Doing too much, he adds, may put people at risk for injury. "You might be weaker than you realize," he says.

Maharam adds: “Do what you can do, and if you can't do it, then don’t,” he says. “Most people who are fit tend to feel worse if they stop their exercise, but if you have got a bad case of the flu and can’t lift your head off the pillow, then chances are you won’t want to go run around the block.”