Your workouts bring a lot of benefits: They relieve stress, improve your heart health, and help you get stronger. But what about exercise and your immune system? Do your workouts help your immune system—or can they actually weaken it?
It’s a question that people are asking more and more as the novel coronavirus spreads. Total cases are continuing to increase, and because it can be transmitted by someone not displaying symptoms, many people are wondering if there’s anything they can do to improve their chances of fighting off the virus, especially if they come into contact with it without even knowing they’ve been exposed.
Hoping for an “immune booster” is understandable, because these are scary times and there are tons of things about the novel coronavirus that we just don’t know yet. But as we reported earlier, there’s no magic pill or supplement that’s going to give your immune system superpowers.
That’s not to say, though, that lifestyle factors like physical activity and exercise don’t play a role in how your immune system works. But it’s just not as simple as “run a mile, fight off a bug.” Here’s what you need to know about exercise and your immune system—especially in the time of the new coronavirus.
How exactly does exercise affect your immune system?
Exercise does affect your immune system, but thinking of it as an “immune booster” isn’t exactly correct.
“In response to bouts of exercise, there is an immune response, and that is a normal immune response,” James Turner, Ph.D., an exercise physiology and immunobiology researcher at the University of Bath in the U.K., tells SELF. “It’s probably more accurate to say exercise stimulates or kickstarts some normal immune processes.”
Here’s what’s happening: When you engage in any kind of physical activity that gets your heart rate up for a sustained amount of time—say, a 30-minute brisk walk or jog, a bike ride, or even some tennis volleying—your body senses it as a type of physiological stressor. As a result, it deploys certain types of white blood cells like neutrophils and lymphocytes (particularly T-cells and natural killer cells) from different parts of your body to flood your bloodstream.
“These very specialized, powerful immune cells are like the Army Rangers of the military,” says exercise immunology researcher David Nieman, Dr.Ph., a professor of biology at Appalachian State University and director of the Human Performance Lab at the North Carolina Research Campus. “They come out and circulate during exercise at a higher rate than normal. Any pathogens are more easily detected and destroyed during this process.”
Soon after your workout, these immune cells start to decline in your bloodstream and even go down to below resting levels. Initially, researchers believed this was evidence of immunosuppression, Turner says, but improved lab techniques actually showed that these cells were just being dispatched to other bodily locations where they continue to perform a process called immune surveillance.
“They go off to other tissues in the body, like the lungs or maybe the skin, intestines, or mucosal surfaces, where an infection might be found,” Turner says.
This whole kickstart to the immune system is only temporary—it lasts about three hours, says Nieman—but it occurs after each bout of moderate to vigorous exercise. So if you continue to exercise regularly, you’ll continue to experience those effects after each session.
But do the physiological responses translate to real-world benefits? Research has shown that people who exercise regularly do tend to get sick less frequently. According to a 2010 study of more than 1,000 adults published in the British Journal of Sports Medicine, people who exercised for at least 20 minutes a day, five or more days per week, reported 43% fewer days with upper respiratory tract infection symptoms than those who were sedentary. And when they did get sick, their symptoms tended to be less severe.