Working Out When You’re Sick, Do or Don’t?


The definition of a disaster for your average active person? Getting sick. One cold or flu can swoop in, sideline you from your workouts and destroy the endurance you’ve been building up for weeks or months. Talk about a double-whammy.

You might feel the temptation to power through and keep pushing yourself to get to the gym or squeeze a run in, despite the nausea or cough. The only question is, “Should you?” Here, Michael Jonesco, MD, a primary care sports medicine physician at The Ohio State University Wexner Medical Center gives you the lowdown on the protocol for working out when you’re under the weather.

How is Your Immune System Affected by a Workout?

The immune system does respond to physical activity. According to Jonesco, mild to moderate physical activity bolsters immune function; this means bumping intensity to 40 to 60 percent of your maximum heart rate (MHR), which you can roughly calculate as 220 beats per minute subtracted by your age. Most of the physiologic changes are positive ones, says Jonesco. “Your white blood cells will function more efficiently, and protective immunoglobulin levels in the mouth and nose may increase, lowering your risk of suffering from an upper respiratory tract infection,” he explains.

On the other hand, intense exercise (70 to 80 percent of your MHR) or prolonged exercise (workouts longer than 60 minutes) can be detrimental to the body’s immune function. “Studies have actually shown increased rates of infections in runners after increasing miles, such as in the weeks following marathons,” he says.

While Jonesco says most of the current literature on illness and exercise focuses on preventing infection, the pros do follow certain guidelines when advising workouts during infection to stay safe. But there are a few things to consider first.

How is Your Body Affected During Illness & How Can that Impact a Workout?

Infections compromise the body’s ability to perform at its peak—just ignore random blips on the radar, like Michael Jordan’s epic 1997 “flu game” performance, says Jonesco. “Illness and fever may impair concentration, coordination, muscle strength and power,” he explains. “Hydration can be significantly altered, draining the heart and other peripheral tissues of a vital resource.” At which point, the heart must work harder to compensate for fluid loss, significantly reducing the body’s ability to effectively participate in most endurance sports. You simply peter out.

However, Jonesco sees patients regularly who simply don’t want to sit out while the body recovers and reboots for exercise. “I remind them high intensity exercise is essentially overloading the body so that it can learn to adapt and respond to increased loads in the future—the body is expending energy to recover and recuperate,” he says. “If you’re sick, these are resources your body simply may not have after an intense workout. Between the illness and the exercise, you’re depleting your body’s energy resources, limiting gains, and possibly slowing your recovery from the illness.”

Basically, hitting the gym too hard may be setting back your long-term progress.

When Can You Workout While Sick & What Can You Do?

If you want to exercise while you’re sick, use “the neck rule,” says Jonesco. Simply put, anything above the neck, like upper respiratory infections or colds, are okay to work through. Anything below the neck, like gastroenteritis or pneumonia, should be viewed as a more serious illness. “Also, any fever of greater than 101° F should be viewed as a systemic illness and would not pass ‘the neck rule,’” he cautions. “Taking days off while having acute or lingering symptoms is recommended to prevent your body from knocking your immune system down further.”

If you pass “the neck rule” and decide to work out, Jonesco says to back off on the intensity. “If you are a runner, you may run, but do so at a slower pace or shorter duration,” he says. “If you do regular resistance training, focus on form and lower the weight—just do everyone in the gym a favor and be vigilant with the hand washing!”

Once your symptoms finally disappear, you’ll probably still be low on energy. With that in mind, Jonesco suggests cutting yourself some slack. “Your body needs to gently resume its previous activity level,” he says. “Consider starting at 50 percent of your usual workout, and advance as tolerated.” But if your symptoms return or you feel totally zapped, listen to your body. Pack it up, hit the couch and catch some Z’s; your workout will still be waiting for you again in a day or two. Promise.



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