“I think this study adds to the growing body of evidence that, along with vaccination, daily physical activity is the single most important thing you can do to prevent severe outcomes from COVID-19,” said Robert Salis, a family and sports medicine physician at Kaiser. Permanente Fontana Medical Center in California and past president of the American College of Sports Medicine. He researched covid and exercise but was not involved in the new study.
However, the study’s findings raise questions about how much — or how little — exercise can best increase vaccine benefits, and whether it’s too late to benefit if you’re already fully vaccinated or about to be vaccinated.
A lot of research in the past year has shown that being active and fit significantly reduces the risk of getting seriously ill if you get covid. Salis led a study, for example, of nearly 50,000 Californians who tested positive for the coronavirus before vaccines were available. Those who regularly walked or otherwise worked before becoming ill were about half as likely to need hospitalization as sedentary people.
Similarly, an August review of 16 earlier studies involving nearly 2 million people concluded that active people were significantly less likely to be infected, hospitalized or killed by Covid than inactive people.
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These links between exercise and protection against Covid make sense, Sallis said. We know “that immune function improves with regular physical activity,” he said, as well as lung health and levels of inflammation, which can otherwise contribute to rising poor outcomes in Covid.
But the studies did not look at whether active people were getting additional benefits from their coronavirus vaccines and boosters.
So for a new study, just published in the British Journal of Sports Medicine, researchers in Johannesburg collected anonymized records of nearly 200,000 men and women from the country’s largest health insurer.
The records included information on people’s vaccinations, covid outcomes and exercise habits, collected from activity trackers and gym visits. Because health insurance provided people with points and rewards for activity, subjects tended to conscientiously record each workout.
The researchers first broadly compared the vaccinated and the unvaccinated. (The Johnson & Johnson vaccine was the only available option at the time.) As expected, the unvaccinated developed covid and became seriously ill in far greater numbers than the vaccinated.
But even among the fully vaccinated, exercise made a significant difference in Covid outcomes, said Jon Patricios, a professor of clinical medicine and health sciences at the University of the Witwatersrand in Johannesburg-Bramfontein, who oversaw the new study.
Vaccinated people who walked or otherwise exercised moderately for at least 150 minutes a week were almost three times less likely to be hospitalized if they developed Covid than those who were vaccinated but sedentary.
More specifically, their vaccines protected them about 25 percent better than the same vaccines in sedentary people.
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The exercise habits of these people met or exceeded the standard exercise guidelines promoted by the World Health Organization and the Centers for Disease Control and Prevention, Patricios said, which call for half an hour of moderate activity at least five times a week.
But even vaccinated people who moved less, exercising just an hour each week, were 1.4 times less likely to be hospitalized than the sedentary, vaccinated group, suggesting their vaccines were about 12 percent more effective than those in people who did not exercise. .
“Doing something was important, even if people weren’t meeting the full guidelines,” Patricios said. “It’s an idea we call ‘small steps, strong shield.’ “
If you can’t fit in a 30-minute walk today, he said, a 10-minute walk is better than skipping exercise altogether.
However, this study was cohort, meaning it shows associations between activity and covid outcomes. While it doesn’t prove that being active makes vaccines more effective, the links were consistent and the effects large, Patricios said.
He also believes the relationship would be similar for exercise and other coronavirus vaccines, such as the Moderna and Pfizer versions, as well as for people who don’t happen to live in Johannesburg.
It is still somewhat unclear how habitual activity increases the response to the vaccine. But Patricios suspects that exercisers’ powerful immune systems encourage the creation of additional battalions of covid antibodies after each vaccination. Lifestyle can also influence the response, including people’s diet and income.
Perhaps most encouragingly, “I think it’s never too late” to start exercising, he said. Have you been inactive? Today’s walk should start priming your immune system to respond with more vigor to the next vaccination or exposure to COVID. “Plus,” he pointed out, “you don’t need a prescription and it’s free.”
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