Special for Infobae of The New York Times.
(Science Times) ; (Phys Ed)
According to new research on exercise and immunization, taking a long brisk walk, jog or bike ride after your next COVID-19 or flu shot could amplify the benefits of the shot. The study, which involved 70 people and about 80 mice, looked at the antibody response after an injection of the flu vaccine or two doses of the Pfizer-BioNTech COVID-19 vaccine. It was found that people who exercised for 90 minutes just after the injection produced more antibodies than those who did not exercise. The additional immune boost, which should help reduce the risk of severe illness from these viruses, did not appear to trigger an increase in side effects.
The results of the study are preliminary and still need to be tested in larger numbers of people. But the results add to growing evidence that being fit and physically active could prime our bodies to respond more strongly to flu and COVID-19 vaccines.
Exercise modifies ‘almost all’ of our immune cells
In general, the relationship between exercise and immunity is clear to everyone. Most studies show that exercise helps protect us against colds and other minor infections of the upper respiratory tract. Being in good physical condition can also ease the severity of an infection if we do get sick. For example, in a study last year of nearly 50,000 Californians who developed COVID-19, those who had exercised regularly before their diagnosis were half as likely to be hospitalized as people who rarely exercised.
On the other hand, extreme exercise could undermine our immunity. Marathon runners often say they get sick after races, and lab mice that run to exhaustion tend to be more susceptible to the flu than sedentary animals.
But in general, exercise is a powerful boost to our immune systems. “The behavior of almost all populations of immune cells in the bloodstream is altered in some way during and after exercise,” concludes a recent review of research on the subject.
Is there a correct ‘dose’ of exercise?
However, few of these earlier studies sought to find out the best time and amount of exercise needed to amplify the effects of the vaccine, and none of them looked at COVID-19 vaccines, as they have only been available since late 2020. So, for the new research, recently published in Brain, Behavior, and Immunity, a peer-reviewed scientific journal, a group of immunobiologists and exercise scientists at Iowa State University, Ames campus, asked people to they were going to get vaccinated against the flu or COVID-19 that they also exercise.
They first invited dozens of healthy adults ages 18 to 87 who said they exercised occasionally to the lab for flu shots. The scientists also coordinated with local COVID-19 vaccination centers to recruit 28 men and women who were to receive their first COVID-19 vaccination. Before the vaccinations, they drew blood from all the volunteers to check their antibody levels.
Then, randomly, these people were asked to sit or exercise for 90 minutes after receiving the vaccine. Previous research had suggested that exercising after a vaccine increased the immune response more than the same level of activity before the injection. They chose 90 minutes of exercise as their overall goal because unpublished research from their lab suggested that this amount of exercise greatly increased the production of a substance in the blood called interferon alpha, which can trigger the creation of immune cells.
Volunteers required to exercise rode a stationary bike or briskly walked for 90 minutes after their shots, either in the lab or outside on sidewalks near COVID-19 vaccination centers. They exercised at a light pace, in order to keep their heart rate between 120 and 140 beats per minute. But the researchers also asked some of the flu-vaccinated volunteers to ride the bike for just 45 minutes, to see if the shorter workout could be just as effective at boosting immunity.
Since antibody levels tend to rise in the weeks after vaccination, the researchers re-bled all volunteers two and four weeks after receiving their vaccinations. (People who received the COVID-19 vaccine received their second injection in the interim, as a second dose from Pfizer must be given three weeks after the first.)
45 minutes is not enough
At one month, the antibody levels of all those vaccinated against the flu or COVID-19 rose quite a bit, as would be expected after receiving a vaccine, but more so in men and women who had exercised for 90 minutes afterwards of the injection. This increase in antibodies was not huge. “But it was statistically significant,” said Marian Kohut, a professor of kinesiology and a member of the Nanovaccine Institute at Iowa State University, who oversaw the new study.
People who exercised also reported no additional side effects after their shots. (They also didn’t experience fewer side effects.)
Interestingly, 45 minutes of exercise in this study was not enough to increase antibodies. The shorter workout may not have increased levels of substances needed to amplify immunity, including interferon-alpha, Kohut said.
The researchers also repeated the flu shot experiment in mice that ran or stood still after the injection. Interferon alpha levels in the blood were checked and found to be higher with exercise. But if the scientists chemically blocked the production of this substance, the animals got a small additional benefit in antibodies from exercise, suggesting that exercise improves response to the vaccine in part by first increasing interferon-alpha levels .
The balance of the results, therefore, is that “if there is time and a safe place to exercise after vaccination,” a 90-minute session of moderate exercise may improve the response to the vaccine, he said. Kohut, without suffering side effects.