Exercise & Fitness
Does exercise protect against COVID-19?
Ask the doctor
Q. My friend, a fitness nut, tells me that regular exercise protects me against COVID and other illnesses. Since I'm terrified of infections, that might just finally get me to exercise regularly. Is she right?
A. Well, get yourself some gym clothes and walking shoes, because your friend almost surely is right. There have not been a lot of studies conducted to see if exercise protects against infections, but there have been a few, and they all point in the same direction.
The largest study, which was conducted here at Harvard Medical School, was published in JAMA Network Open in February 2024. The study included nearly 62,000 people ages 45 or older. They were followed from before the start of the COVID pandemic (in early 2020) through the end of 2022. Information was collected about many factors that could affect a person's vulnerability to infection, such as chronic illnesses, socioeconomic status, and lifestyle factors. The study also tracked whether the people got COVID and how seriously ill they were with COVID.
Finally, the study determined how physically active people were: 69% were "sufficiently active," meaning their weekly activity level was in the healthy range — at least 150 minutes per week of moderate to vigorous physical activity. As for the rest, 11% were "insufficiently active," and 20% were inactive.
The study showed conclusively that compared to the people who were inactive, those who were sufficiently active were 10% less likely to develop COVID and 27% less likely to be hospitalized for COVID. This was particularly noticeable among women. Unfortunately, people who were insufficiently active did not do much better than those who were completely inactive: you really need a "healthy" amount of physical activity each week to be protected against COVID. (Not surprisingly, the study also showed that people who got a COVID vaccine were much less likely to get COVID and to be hospitalized.)
Other studies have shown that regular exercise protects against other infections, like influenza, so the results of this study are not really surprising. And, as we often report, regular exercise also protects you against heart disease, cancer, dementia, depression, and other major illnesses.
How does regular exercise achieve these healthy benefits? Science is just beginning to learn the answer. Exercise enhances the ability of several types of white blood cells to fight infection. It stimulates the body to produce antibodies in the lining of the nose, throat, breathing tubes, and lungs, which fights infection. At the same time, regular exercise keeps the immune system from overreacting to infections and waging a battle that injures not just the invading germ but also the body itself.
You've heard it before in these pages: no pill ever invented protects your health as much as does regular exercise.
Image: © RyanJLane/Getty Images
About the Author
Anthony L. Komaroff, MD, Editor in Chief, Harvard Health Letter; Editorial Advisory Board Member, Harvard Health Publishing
Disclaimer:
As a service to our readers, Harvard Health Publishing provides access to our library of archived content. Please note the date of last review or update on all articles.
No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.
