How Exercise Affects Your Immune System

We have discussed ways you can use nutrition to boost your immune system here. But have you considered the amount of daily exercise you’re getting and what is healthy and what isn’t? This article via Self Magazine discusses how physical activity affects your health and immune system.

Does Exercise Actually Help or Hurt Your Immune System?

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.

That’s not to say, though, that exercise will automatically trigger your immune system to annihilate any germ invader it sees—it’ll just help you improve your odds of fighting it off, Nieman says. It’s not a get-out-of-jail-free card by any means (more on that below).

Is more exercise better—or can too much hurt your immune system?

If a moderate amount of exercise can stimulate your immune system, will longer or more vigorous exercise have a greater effect? Or can it actually weaken your immune system?

That’s a question that’s been hotly debated for years, and as with many questions in the field of science, there isn’t exactly a consensus on the answer. According to Nieman, vigorous exercise of a long duration—think 90 minutes or more, like you’re racing a half marathon or a marathon—starts to over-stress your immune system, which can temporarily impair its ability to do its job and leave you more vulnerable to infection during this time. That’s what’s known as the open window hypothesis. (HIIT, on the other hand, isn’t linked to such immune suppression even though it involves super-intense work, probably because of its rest intervals and shorter overall duration, Nieman says.)

Now, evidence does show that some elite athletes get sick with upper respiratory infections (URI) after competition, but Turner and other experts argue that it’s not exactly the exercise that’s to blame: “It is misleading to conclude from existing evidence that exercise is the causative factor of URI among athletes,” Turner’s team wrote in a new debate paper on exercise and immune suppression published in Exercise and Immunology Review this year. After all, Turner tells SELF, even though some immune cell counts are lower after intense exercise, it isn’t because they’ve died off—they’ve just gone off to other tissues in the body to continue their infection patrol.

The more likely reason for sickness after intense competition like marathons—whether for elite athletes or recreational exercisers—Turner believes, is not just about the exercise. It likely also has to do with the environment, he says. Think of marathon corrals at the starting line at big-city races: They’re shoulder-to-shoulder people, and the course itself doesn’t really clear up much after, either.

“You are exposed to thousands of people there,” Turner says—so those who are sick with viral or bacterial infections can subsequently transmit them to you. That can be directly through nasal droplets that enter your nose or mouth, like through another person’s cough or sneeze, or by touching a surface that a person who is sick has touched and then touching your own mouth, nose, or eyes.

Those mass-participation events can obviously be a nightmare for virus spread—which is why races like the Boston Marathon have postponed their competition among coronavirus fears (even before the state’s stay-at-home advisory was issued)—but they’re not the only factor likely involved, either. Other issues that could cause immune suppression could have been at play leading up to the big event too.

“Everything is multifactorial with the body and with the immune system,” says Nieman. “The physiological effects of heavy exertion on the immune system is one factor, but then if they travel and get on planes, then they don’t sleep well, that introduces other stressors to the immune system. And then if they are undergoing psychological stress, that’s another one.”

Continue reading here.

“Does Exercise Actually Help or Hurt Your Immune System?” Written by Christa Sgobba

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