The volunteers who exercised then rode a stationary bike or walked briskly for 90 minutes after their shots, either in the lab or outside on sidewalks near Covid shot sites. They exercised at a mildly challenging pace, aiming to keep their heart rate between 120 and 140 beats per minute. But the researchers also asked some of the flu-vaccinated volunteers to cycle for just 45 minutes, to see if the shorter workout might be just as effective at boosting immunity.
February 9, 2022, 6:33 a.m. ET
Because antibody levels tend to build up in the weeks after vaccination, the researchers bled everyone again two and four weeks after the injections. (People who received the Covid vaccine received their second injection in the meantime, as a second Pfizer injection is due three weeks after the first.)
45 minutes is not enough.
After a month, everyone’s antibody levels against the flu or Covid vaccine increased substantially, as expected after receiving a vaccine. But they were higher in men and women who had exercised for 90 minutes afterwards. This antibody bonus was not huge. “But it was statistically significant,” said Marian Kohut, a professor of kinesiology and a member of the Iowa State Nanovaccine Institute, who oversaw the new study.
The exercisers also reported no additional side effects after their injections. (They also didn’t experience fewer side effects.)
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Interestingly, 45 minutes of exercise in this study was not enough to increase antibodies. The shorter workout probably didn’t increase levels of substances needed to amplify immunity, including interferon alpha, Dr. Kohut said.
The researchers also repeated the flu shot experiment in mice that jogged afterward or stood still. The researchers checked their blood levels of interferon alpha and found them higher with exercise. But if the scientists chemically blocked production of the substance, the animals derived a small additional antibody benefit from exercise, suggesting that exercise improves response to the vaccine in part by first raising interferon-alpha levels.
The bottom line of the results, then, is that “if you have time and a safe place to exercise after vaccination,” a 90-minute session of moderate exercise may boost your response to the vaccine, said Dr. Kohut, without adding effects