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Exercise has a protective effect against COVID-19, a review found. Image credit: BONNINSTUDIO/Stocksy.
  • Regular physical activity may be linked to a lower risk of developing COVID-19.
  • Individuals who exercise regularly may be less likely to experience severe symptoms of COVID-19 and less likely to be hospitalized or die because of the disease.
  • 2.5 hours of moderate-intensity exercise or 75 minutes of vigorous-intensity exercise each week provides the best protection.

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A 2021 Kaiser Permanente study of about 49,000 people with COVID-19 found that regular physical activity was strongly associated with a reduced risk for severe outcomes from the disease.

With a new systematic review and meta-analysis published recently in the British Journal of Sports Medicine, a team of Spanish researchers set out to evaluate the current evidence on the effect of habitual physical activity on COVID-19 outcomes.

The review also aimed to quantify how much regular physical activity a person would need to have a reduced risk of severe outcomes if they do develop the disease.

The review found that regular physical activity is related to a lower risk of developing COVID-19, a lower likelihood of experiencing severe symptoms in individuals who do develop the disease, as well as a lower likelihood of being hospitalized or dying because of it.

Specifically, the analysis found that individuals who regularly included physical activity in their schedules had a 11% lower risk of developing COVID-19. Those who habitually exercised and developed COVID-19 had a 44% lower risk of developing severe illness, a 36% lower risk of being admitted to hospital, and a 43% lower risk of death from COVID-19.

The researchers found that 2 and a half hours of moderate-intensity exercise or 75 minutes of vigorous-intensity exercise each week provides the best protection.

Dr. Yasmin Ezzatvar, co-author of the paper and a doctor of physical therapy who lectures at the University of Valencia in Spain, told Medical News Today that she and the other researchers were motivated to conduct this review because the work was needed “to inform clinical decisions and public health strategies.”

A body of work by other researchers has found that individuals who make time for regular physical activity face a reduced risk of acquiring infectious diseases.

A systematic review published in 2021, for instance, found that habitual moderate-to-vigorous physical activity is associated with 31% lower prospective risk of infectious disease and 37% lower risk of infectious disease-related mortality.

“The health benefits of regular physical activity and exercise are well documented,” Dr. Ezzatvar told MNT. “Regular physical activity elicits a plethora of physiological adaptations that improve health either directly or indirectly.”

A number of factors may be behind the protective effect of habitual exercise.

“There is evidence that regular physical activity might contribute to a more effective immune response, providing enhanced protective immunity to infections, which could explain the relationship between exercise consistency [and] COVID-19 [risk].”

– Dr. Yasmin Ezzatvar, study co-author and doctor of physical therapy

Regular exercise, Dr. Ezzatvar added, also lessens the risk of individuals becoming obese or developing hypertension, two conditions that demonstrably increase the risk of experiencing more severe outcomes from COVID-19.

For the analysis, two of the researchers searched through three major research databases looking for studies published between November 2019 and March 2022 relating to COVID-19 and physical activity. Out of 291 studies that fit the criteria, the researchers selected 16 studies for the analysis.

Almost 2 million adults participated in these studies. Of these, over half were women and had an average age of 53. The studies were carried out in countries all over the world, including Iran, Canada, and Sweden.

Dr. Danielle Kirkman, assistant professor of kinesiology and health sciences at Virginia Commonwealth University’s College of Humanities and Sciences in Richmond, VA, told MNT:

“It’s a nice study because it sort of combines a lot of different studies from all over the world to kind of show something that we predicted might happen at the beginning of the pandemic, which was that those who are less active are probably predisposed to having some worse outcomes related to COVID-19.”

Dr. Kirkman found it especially interesting that the study found that 2.5 of moderate-intensity or 75 minutes of vigorous-intensity exercise each week provide the best protection.

The finding matches the physical activity recommendations for adults issued by the United States Department of Health and Human Services.

“The study certainly lined up really well to show that those who were hitting that goal had better outcomes if they did [develop COVID-19].”

– Dr. Danielle Kirkman, assistant professor of kinesiology and health sciences at Virginia Commonwealth University

The researchers pointed out several limitations with their results. For one, the review only looked at studies that concerned the Beta and Delta variants of SARS-CoV-2. Additionally, many of the studies used subjective assessments of physical activity levels like self-reported questionnaires.

In their paper, the researchers also acknowledge that the authors of the individual studies could have failed to sufficiently adjust for covariates or characteristics of the participants in the study.

“So we now know that physical activity is highly linked with noncommunicable diseases such as diabetes, obesity, cancer, that kind of thing,” Dr. Kirkman told MNT.

“And I think in a study, a meta-analysis like this, it’s very difficult to control for all of those and […] weed out what is exactly [related to lower levels of] physical activity and what might be other disease-related [outcomes],” Dr. Kirkman added. “[T]ake that into consideration when interpreting the results.”

Dr. Ezzatvar would like to see future studies that look at how individuals who regularly include physical activity in their routines do with new variants of SARS-CoV-2 and that also consider the impact of vaccinations and new treatments for COVID-19.

“We also need more studies that allow us to understand how to help people with persistent COVID-19 symptoms,” she told MNT.

Dr. Ezzatvar and the other Spanish researchers are currently working on a study that will compare the effects of 6 weeks of strength training versus standard care on the clinical status of patients with persistent COVID-19 symptoms.

“If successful,” she said, “it is hypothesized that this trial would provide evidence that exercise training has potential for patients with post-discharge symptoms after COVID-19.”