Not everyone who feels under the weather should exercise.

By Ray Hainer
Updated: February 19, 2019

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.

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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.”

Even if you pass the neck test and are determined to get a workout in, you should take it easy at first. “To be prudent, I'd recommend cutting exercise duration and intensity when symptoms are present,” says Woods.

Daryl Rosenbaum, MD, director of the Sports Medicine Fellowship at the Wake Forest University School of Medicine, recommends that people with colds begin working out at 50% intensity. If symptoms improve after the first five to 10 minutes (as they often do), you can gradually increase the length and effort of your workout up to about 80% to 90% of your usual routine.

“Moderation is the key,” says Dr. Rosenbaum. “Studies have shown that people suffering from the common cold who get up and get moving actually feel better. If you go too far, however——either with extreme short-term activity or long-term overtraining——the immune system weakens. A viral cold that is allowed to linger for longer than normal could create sinus conditions that are ripe for a bacterial sinusitis to take over.”

There are some other precautions to keep in mind. Staying hydrated during exercise is always important; it is especially so if you're planning to exercise with a cold. The nasal drainage associated with colds can hasten dehydration, and some over-the-counter cold remedies containing antihistamines (many cough syrups, for instance) can dry you out further, Dr. Rosenbaum points out.

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Don't spread——or catch——more germs at the gym

If you work out in a public gym, be extra vigilant when exercising with a cold. Germs can be transmitted through the air and through any person-to-person contact, so if you use a treadmill, gym mat, or barbells, be sure you're wiping down the equipment. And avoid touching your face after handling equipment; you can pick up germs that will be more likely to infiltrate your body that way.

Your vulnerability to upper respiratory tract infections spikes for several hours starting just after a strenuous workout, studies suggest. So if you've just stepped off the treadmill after a 10-mile run, give that sweating, coughing, and sniffling stranger in the locker room a wide berth.

“Regardless of whether you're exercising moderately or intensely, you want to take precautions against infection,” says Woods. “Clean your exercise equipment before and after, use a clean cup to get water from the fountain, and try to pick a machine away from other people.”

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