It can be frustrating to be sidelined by a cold or other virus, but working out when you are sick can worsen symptoms and affect your recovery.

NYU Langone sports health specialist Dennis A. Cardone, DO, explains the importance of listening to your body to help determine when it’s safe to exercise. “Not being able to exercise is not an easy prescription to fill, but there are certain symptoms that should be a warning sign to stop exercising,” Dr. Cardone says.

If you feel up for it, it’s safe to exercise when your symptoms are all above the neck, such as a mild sore throat, runny nose, or congestion, Dr. Cardone says. Even so, it’s best to take it easy and reduce your workout’s intensity or duration, especially if you feel like you have less energy than normal.

Don’t exercise when symptoms are below the neck, such as fever, vomiting, diarrhea, or a productive cough. These are signs that your body is busy fighting off infection and would benefit from rest. “Remember, when you have a fever, your body is working overtime to fight the infection. Adding exercise will further stress the system,” Dr. Cardone says.

While regular exercise has been shown to boost immunity, there’s no truth to the notion that an intense workout aids recovery. “The idea of exercising so you can sweat out a fever is a myth,” Dr. Cardone says.

Exercise also increases your heart rate and body temperature and can increase the risk of dehydration when you are already running a fever, which is dangerous. Once your fever breaks, you should wait at least a few days before resuming exercise. During this time, Dr. Cardone recommends staying well hydrated, eating a balanced diet, and avoiding overexertion.

After being sick, listen to your body, rest when you need it, and ease your way back into your normal workout routine, he says. It may take a few weeks for you to get back to your usual intensity and duration, so be patient.