workout when sick

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The Potentially Valid Excuse: You're Sick

You should absolutely skip your workout if: The problem is happening below the neck.

The reason: Body aches, fever, chest congestion, diarrhea or other digestive issues can all be made worse by exercise, says Lipi Roy, MD, a clinical instructor in medicine at Massachusetts General Hospital in Boston. These symptoms are often accompanied by dehydration, too, and sweating won't help the matter. (Issues above the neck, such as a runny nose, scratchy throat or mild cough, though, may actually be improved by moderately intense exercise.)

When you can exercise again: Once symptoms subside, but be sure to dial back the intensity on the first session. If you had a fever, wait until your temperature has been normal for at least two days before resuming your workout routine, says Michele Olson, PhD, a professor of exercise science at Auburn University.