Exercising can protect you from getting sick -- here's how much you need

Need a reason to get active? Exercise boosts your immune system, can protect you against illness and even help you recover faster if you get sick. Here's how much you need to get those benefits.

Mercey Livingston CNET Contributor
Mercey Livingston is a health and wellness writer and certified Integrative Nutrition Health Coach. She's written about fitness and wellness for Well+Good, Women's Health, Business Insider, and Prevention.com among others. When not writing, she enjoys reading and trying out workout classes all over New York City.
Mercey Livingston
5 min read

Exercise can help boost your overall health and immune system.

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Now more than ever, people are looking for ways to stay healthy, relieve stress and feel better. For many, exercise fits that bill. It can make you feel happier, help you blow off steam and have more energy, among other benefits. But one thing many people are wondering in the face of a global pandemic is: Can exercise really boost your immune system? And if you're already sick, can it help you recover faster?

Exercise and immunity is an often-debated topic and researchers have been studying it for years. On one hand, researchers say intense exercise without sufficient recovery can make you more susceptible to illness, but another study in 2018 claims to debunk the myth that intense exercise suppresses immunity. A recent analysis published in the international journal Exercise Immunology Review showed that regular, moderate exercise is beneficial for a healthy immune system. 

Since the evidence is mixed and also vastly depends on what kinds of exercise you do and how long, how often you do it -- I decided to tap the expert advice of a doctor and infectious disease expert to shed some light on the topic. Below, you'll find her insights on the connection between the immune system and exercise, as well as an overview of what science has to say about the topic. 

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How exercise affects your immune system

When people say that "exercise boosts your immune system" they are most likely referring to the short-term effect exercise has on your white blood cells, the cells needed to fight infections. "Any kind of stress on the body -- whether that's a workout or infection, or extreme environmental condition -- the normal response that our bodies have to stress is to increase the number of white blood cells in the blood. They are out there to kind of patrol for anything that might be harmful, any toxins and anything that might cause damage," says Dr. Sandra Kesh, who specializes in infectious disease and internal medicine. 

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Kesh also said that your workout does not have to be that strenuous to trigger the immune response, so almost any exercise activity that you do for about 15 minutes at minimum per day can help.

Besides the effect that exercise has on your white blood cell count, it can also provide a lot of other health benefits that all add up to help prevent you from being sick. "Getting into a routine of good exercise does give yourself some protection from getting the infection (COVID-19), having a severe form of the infection and helps mental-health wise. We know stress is a big problem for the immune system and it really does hinder our body from fighting off infection and so exercise is a good way to keep stress levels in check," Dr. Kesh says. 

The debate on intense exercise and immune suppression 


Intense exercise may have a dampening effect on your immune system.

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Health experts like Dr. Jordan Metzl and other researchers say you can have too much of a good thing when it comes to exercise. These experts say that doing long, intense workouts, especially without sufficient rest and recovery days, can mean bad news for your immune system and even make you more susceptible to illness. One 2019 study shows that it's clear that exercise can improve health and immune system function, but periods of intense training can put you more at risk for illness. Other researchers have debated the topic, going back and forth on exactly what effect intense exercise can have on immune health. 

No matter how you look at your fitness routine, we know that overtraining is bad news for a lot of reasons (and probably, for your immune system) and prioritizing recovery, rest and sleep is key. To be safe the best thing you can do is to  get your workouts in, but don't push yourself too hard, make sure you take ample rest days and time to recover. Also, Dr. Kesh suggests that now is not the time to train for a marathon or some other extreme fitness event that will require putting your body through a lot of stress and strain. Save that for when the pandemic is over and instead prioritize moderate, regular exercise. 

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How much exercise you really need to stay well 

You definitely don't need to run a marathon to stay well, and you don't even need to exercise for an hour a day, for that matter. Experts, like Dr. Kesh and the Department of Health and Human Services say you only need about 150 minutes of moderate exercise per week to stay healthy.

"We know that people who exercise, even moderately 15-20 minutes a day, most days of the week (5-6 days), they get sick less often. There was a study that showed they had fewer sick days per year, and when they got sick they weren't as sick compared to people that were largely sedentary," Dr. Kesh says. 

"I like to follow what the Department of Health and Human Services says, which is 150 minutes per week for moderate exercise. If you are exercising vigorously, then 75 minutes a week. And ideally you spread that out so you are getting some exercise most days. That amount of exercise kind of keeps your immune system trained but not overtaxed. So if it does get some kind of foreign invader it can respond but not be overwhelmed," Kesh says. 

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You should only exercise once you feel you have recovered from an illness.

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Exercise and COVID-19 symptoms and recovery

Like Kesh mentioned earlier, patients who have COVID-19 and followed an exercise routine before they were sick tend to have less severe symptoms and recover faster. 

"One of the things we find is that a complication in people who have severe infections is Acute Respiratory Distress Syndrome (ARDS), a lung condition, and it tends to happen in people who don't exercise and their lung capacity is not as expanded as people who exercise regularly," Dr. Kesh said. Dr. Kesh also added that experts don't fully understand what is happening in the lungs for people with severe COVID-19 infections, but the healthier that person was before they got infected, the better the outcome.

"We do know the healthier you are going into any infection, the more likely you are to recover and recover more quickly. So your starting physiologic state is one of the biggest predictors of where you end up after the infection is over. And so I tell my patients, now is the time to quit smoking, now is the time to start an exercise routine, now is the time to start eating healthy, because doing those things will put you in a better place to fight off the infection if you do get it."

As for COVID-19 recovery, Dr. Kesh advises taking things very slow once you feel like exercising after having the virus. You don't want to do too much too soon, and don't try to jump back into your routine full force. "Take it one day at a time and work your way back up (when you are recovering). But going back to an exercise routine absolutely helps with recovery, as long as you do it in a step-wise approach and don't bite off more than you can chew too early on because the disease could reemerge and you could start feeling worse again and set yourself back," Kesh said. 

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The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.