Should You Work Out When You’re Sick?

“The old recommendation that you should just take it easy, stay in bed and allow your body to recover is generally not a good idea,” Schaffner says. “The more time you spend horizontal, the weaker your body will become.”

In other words, ignore that little voice inside — implanted by your mother however many years ago — that insists on staying in bed. “When you’re sick, you should get yourself up to the degree your body will let you,” Schaffner says. “The more time you spend horizontal, the worse it is — physically and psychologically. Even just walking around the house will help your sense of well-being. It will also help prevent you from developing complications.”

Keep reading to determine how physically active you should be on your road to recovery.

1. Listen to your body.

Your energy levels will dictate what and how much you should do. “I advise patients to do low-intensity exercise that makes them feel good,” Ren says. “For people with mild illness, light physical activity like walking or gentle yoga can be beneficial, as it can improve circulation and mood. However, it’s essential to listen to your body. If exercise makes you feel worse or more fatigued, it’s best to rest.”

Sleep is an essential part of the prescription for almost any illness. Research shows that immunity and sleep have a two-way relationship. As you sleep, your body releases cytokines, signaling proteins that help control inflammation in your body. Some cytokines also help promote sleep.

2. Fever? Don’t even think about it.

“A fever is usually a sign that your body is actively fighting an infection,” Ren says. “In such cases, it’s important to rest and not engage in physical activity, as exercise can raise your core body temperature further, potentially making you feel worse.”

You’re more prone to dehydration if you’re running a fever. “With any respiratory infection — and that includes the more serious ones like COVID-19, RSV and influenza — keeping up with your fluids is very important,” Schaffner says. “If you get dehydrated, you’re predisposed to the more serious complications of pneumonia.”

With a fever, he says, you lose fluids through what’s known as insensible loss. That’s the name given to the hard-to-measure body fluid you lose daily from, say, the respiratory system or skin. “We can’t sense that from our skin and mucous membranes we are losing fluid to the surrounding atmosphere, but we do that when we have a fever, so it’s even more important to make sure you’re restoring your fluid balance,” he says. 

3. Skip the sweat session.

If you’re well on your way to feeling like yourself again, you may think sweating out your sickness is a good idea. It isn’t.

“Exercise can have both positive and negative effects on the immune system,” Ren says. “Low- to moderate-intensity exercise can have a mild immune-boosting effect, possibly by promoting the circulation of immune cells and enhancing your body’s ability to combat infections, while prolonged or high-intensity exercise can trigger decreased cellular immunity.”

What’s more, the setting for that sweat session — in all likelihood your gym — automatically makes you a super-spreader. With the common cold, you’re most contagious during the first 48 to 72 hours of feeling sick, but you can continue to spread your cold for up to two weeks.

“One thing you don’t want to do is go to the gym and give whatever you have to everybody else,” Schaffner says. “If you do strength training three times a week, first of all, good for you. But do what you can at home while you’re ill. You don’t have to stop completely, but wait until you recover and you’re sure you’re not infectious before you go back to the gym.”