Cold or Flu? How to Know If You're Too Sick to Work Out

Are you sniffling, sneezing, and coughing? If you’re like most people, you probably don’t relish the thought of lacing up your sneakers and hitting the road (or the gym) when you have a cold or flu. But those who persevere when they're sick and don’t break their exercise routine may be on to something. Some experts argue that moderate exercise can actually have a beneficial effect on cold symptoms, according to the American College of Sports Medicine.

Exercisers in general tend to catch fewer colds than their sedentary counterparts, research suggests. If done regularly, moderate exercise can halve the number of days you spend with cold symptoms, according to a series of studies conducted in the 1990s. While working out may help fend off viruses, even the most dedicated gymgoer will come down with a cold at some point.

Not everyone who feels under the weather should exercise, however.

What’s the neck rule?
Experts like to cite a rule of thumb known as the “neck rule.” If your symptoms are all located above your neck (stuffy nose, scratchy throat, headache), you almost certainly have a head cold and can hit the road or treadmill safely. If, on the other hand, you have a fever, congestion in your chest and lungs, or feel achy, it is probably a sign of flu, bronchitis, or another more serious ailment, and you should rest up. (Exercising with a fever will make you more vulnerable to dehydration, among other ill effects.)

But the neck rule isn’t foolproof, and a little common sense is always a good idea. “The above-the-neck rule is a good one, but I’d say severe above-the-neck symptoms warrant cessation from regular exercise until the symptoms abate,” says Jeffrey Woods, PhD, professor of kinesiology at the University of Illinois at Urbana-Champaign. “ Even Olympic athletes need a day or two off every once in a while.”