The Scientist: Jeffrey A. Linder, M.D., an associate physician at Brigham and Women’s Hospital and associate professor of medicine at Harvard Medical School

The Answer: There is no hard and fast rule you need to follow when it comes to working out under the weather. You really need to listen to your body—though of course it helps to know what to listen for.

If you have just minimal respiratory symptoms—stuffy nose, mild chest congestion, slight sore throat—exercise shouldn’t be a problem, and might even stimulate an endorphin rush that makes you feel better for a while. You may also get a psychological boost from being active versus not doing anything all day.

Of course, bear in mind that if you go to the gym you could spread your germs to other people. If you start feeling bad, have worsened symptoms, or notice any new symptoms as you work out, you should stop, rest up and try again another day. When you are sick, your body needs some amount of rest to recuperate because it’s working harder to fight the infection than it does when you are well.

If your symptoms are more severe, or if you have a fever, skip a day to let your body marshal its resources for fighting the infection. Dr. Linder emphasizes that the line between a little sick and too sick will be different for everyone, but here’s what he does: He rides his bike to work every day and says that if he’s well enough to be at work, he’s well enough to ride. But when he calls in sick, the bike stays in the garage.

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