Is it healthy to work out when you have the flu?

While some people take their sick days very seriously without having any plans to leave the couch whatsoever, others might rather hit the gym so they don’t mess up their workout schedules. But what’s the healthy protocol on exercising when you’re feeling under the weather?

While working out is a great method for preventing illness, even for just 30 to 45 minutes a day, when you’re already sick, it might be a better idea to skip the gym, depending on how severe your symptoms are. “Exercise is great for prevention, but it can be lousy for therapy,” David Nieman, a professor and director of the Human Performance Lab at Appalachian State University, told Time. “If your symptoms are neck up—things like sinus and nasal congestion, sort throat, etc.—exercise neither helps nor hurt.”

“I know that not exercising at all is a bitter pill for many to swallow. But if you have the flu or anything that causes fever or muscles aches or weakness, that’s a time to not exercise at all.” —David Nieman, public health professor

If you have a flu, on the other hand, stay far, far away from those exercise machines. Some people think they should sweat out the virus, but experts say that’s a horrible idea. According to Mariane Fahlman, PhD, a professor of health education at Wayne State University, the immune system works overtime trying to fight off the flu or other infections, and since exercise is a form of physical stress, your workout acts as another obstacle in the way of your body doing its job.

Furthermore, past studies have shown that exercising while flu-ridden actually led to chronic fatigue symptoms that lasted for years due to the virus sticking around in a less-severe form. “I know that not exercising at all is a bitter pill for many to swallow,” Nieman said. “But if you have the flu or anything that causes fever or muscles aches or weakness, that’s a time to not exercise at all.”

Instead, experts recommend waiting an entire week after your fever goes away before exercising again. And once you’re back on the wagon—or, er, hitting the pavement—it’s best to start slow with long walks before jumping right back into intense workouts. And definitely don’t push through any muscle aches or weakness—wait for those to go away, too. It stinks sitting on the sidelines for a while, but you’ll be better for it in the end.

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