Sweating Out a Cold: Working Out When Sick

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You may have heard friends say they’re going to the gym in hopes of sweating out a cold — but does it really work? Katherine Meyers, DO, UnityPoint Health explains all the things you should keep in mind if you’re considering working up a sweat while fighting off a bug.

What the Science Says About “Sweating Out” a Cold

When deciding if you should sweat out a cold, it’s helpful to understand the effect exercise has on the body. Dr. Meyers says working out regularly boosts the body’s metabolism and immune response. However, an intense workout has the opposite effect.

“During light to moderate exercise, our body releases chemicals to repair itself and decreases levels of stress hormones (cortisol). This is helpful in fighting infections. When exercise gets too intense, we produce more cortisol to help our body get extra energy. This unnecessary use of energy weakens the cells of our immune system that fight infections and lowers our immunity temporarily, because energy our immune system needed was wasted “fighting” a battle our body didn’t need to fight (accomplishing a high-intensity workout)," she says.

Dr. Meyers adds, “There’s an interesting study on exercise and illness in mice. Three sets of mice were given the influenza (flu) virus. The first set included sedentary (inactive) mice and, interestingly, the fewest number of mice from this group got flu symptoms. The second set did 120 minutes (about 2 hours) of running on a treadmill. Surprisingly, they had the highest number of flu infections and death. The third and final set of mice performed light running on a treadmill. This group had a higher number of flu infections than the sedentary group, but they recovered faster and had the lowest death rate. From this experiment, scientists drew the conclusion that light exercise can expose you to more flu, but you can recover faster, have fewer complications and less risk of death.”

The Good & the Bad of Exercising When Sick

If you’re wondering how much working out is too much while ill, Dr. Meyers says any mild to moderate, low-impact exercise for shorter periods of time, like 30 minutes, is OK. Maintaining physical activity allows the body to boost immunity and metabolism to fight off infections, like a cold. Here are beneficial ways to exercise while sick:

  • Walking
  • Light jogging (as long as you don’t feel more breathless than normal)
  • Yoga
  • Meditation

If you’re exercising when sick, make sure to focus on hydration. Drink plenty of fluids and keep electrolytes in check with drinks containing electrolytes, such as low-sugar sports drinks or Pedialyte. Dr. Meyers suggests avoiding full-sugar sports drinks, because too much sugar too quickly can lead to diarrhea, which worsens dehydration.

On the other hand, if you have a cold, exercising for long amounts of time, like two hours, is not wise and neither are any high-intensity options. Exercises you should skip while sick includes:

  • Long races (like marathons)
  • Heavy lifting
  • Intense, interval-style workouts

Dr. Meyers also says, “If your body is working to fight an infection, you may be weaker than normal and more vulnerable to injury. Your lungs may not be able to transfer oxygen to your blood as easily, which places extra strain on the heart while exercising. Monitoring your ease of breathing while exercising is essential to staying safe. You should be able to easily hold a conversation and not feel short of breath.”

Cold Symptoms You Shouldn’t Ignore

Dr. Meyers says there are illness signs to never ignore, especially if you're considering moderate to heavy exercise. If you notice any of the following symptoms, it's best to stay home, rest and consider calling your healthcare provider for evaluation.

  • Fever
  • Muscle & joint pain
  • Vomiting
  • Headache
  • Diarrhea

“These symptoms may suggest the infection is widespread, and your body most needs hydration and rest to send all your available energy toward fighting the infection,” Dr. Meyers says.

She adds, “It’s especially important to maintain hydration if losing fluids through vomiting or diarrhea, because dehydration can turn a typical illness into an emergency. So, excess fluid loss through sweating would be more risky than beneficial.”

Germs at the Gym

If you’re not already sick, the gym can be a risky place. Dr. Meyers says to keep in mind that a cold or flu can easily spread from person to person in an indoor gym, and you should take precautions to protect yourself.

When you're in the gym, it’s easy to catch infections from other people. You're in close quarters where activities may induce more coughing and bodily fluid loss. Make sure you wipe down the equipment before and after use. If you, or others around you, are coughing, you should be using a mask. Wash your hands before and after working out,” Dr. Meyers says.

If you’re thinking about doing a short workout outside, Dr. Meyers says you really should check the forecast first.

“Avoid extreme temperatures that can quickly change your core body temperature. Your body sometimes uses temperature regulation to kill or weaken viruses and bacteria that cause infections.”

For example, running in the rain can cool down your body and prevent it from raising its core temperature to fight the infection.

Post-Illness Return to Activity

Once the symptoms become mild, Dr. Meyers says it’s OK to return to light to moderate exercise with caution.

“Only your body can tell you how quickly you can resume your prior level of activity. You should keep in mind that you've used up your reserves inside to fight off the infection. Start low and go slow. Hitting the gym hard to make up for lost time can lead to muscle damage and other injuries. Specifically, if you’ve been dehydrated, your kidneys may have suffered also, and the kidney needs to clear toxins created by exercise,” Dr. Meyers says.

What the Doctor Recommends

Overall, Dr. Meyers says to listen to your body before exercising when sick. It's important to get in at least basic motion while ill to avoid risk of complications, such as blood clots and pneumonia, but if you choose to do structured exercise while ill:

  • Keep it mild (monitor breathing)
  • Aim for shorter amounts of time
  • Take frequent breaks
  • Hydrate properly


If you’re experiencing flu-like symptoms, contact your doctor, so you can start feeling better faster.