Why the Gym is Risky for COVID-19, and Tips for Keeping Safe – TIME

May 24, 2022

COVID-19 has been frustrating for gym rats. Even before scientists knew much about this particular virus, it was pretty clear that breathing heavily in a confined space with lots of other people around doing the same was an easy way to catch a respiratory illness, and gyms were among the first businesses to close early in the pandemic. These suspicions have since been borne out by science: aerosolstiny droplets that spread through the air when we breathehave been identified as a major source of COVID-19 transmission, especially when people are breathing faster and more deeply. Throughout the pandemic, exercise at spin classes, fitness clubs and sports games has been identified as the source of dozens of new cases.

Now a new experiment has given us a more exact sense of just how many aerosols a single person can spew during an intense workoutand the results arent pretty. According to research by scientists in Germany published in PNAS on May 23, people emit about 132 times as many aerosols per minute during high intensity exercise than when theyre at rest, which the researchers warn raises the risk of a person infected with COVID-19 setting off a superspreader event. At rest, people emitted an average of 580 particles each minute, but during maximal exercisein which researchers gradually increased intensity until the subjects were exhaustedpeople emitted an average of 76,200 particles a minute.

The study authors acknowledge that their work has limitations. First and foremost, the sample size was just 16 people. In addition, none of the subjects were infected by COVID-19; in the paper, the researchers note there was no way to do so safely, due to ethical concerns about the health risks for participants.

Nevertheless, there were some valuable findings to come out of the work. [As an exercise physiologist], and we knew before that when you exercise, theres more air coming out of a person, says Henning Wackerhage, a co-author and professor of exercise biology at Technische Universitt Mnchen. But we didnt know before, and which, quite frankly, I didnt expect, is that also when we exercise hard: there are more particles per liter of air.

The unusual experiment design enabled the researchers to get a more exact sense of the particles released. While exercising on a stationary bike, each of the 16 subjects breathed clean air through a silicone face mask, and then exhaled into a plastic bag. This enabled the researchers to eliminate sources of contamination and get more reliable results, says Christian Khler, a professor at the Institute of Fluid Mechanics and Aerodynamics at Universitt der Bundeswehr Mnchen who co-authored the study.

Some of the participants also emitted much more aerosols during high-intensity exercise than others; in particular, fitter people with more experience in endurance training emitted 85% more aerosols than people without such training. Dr. Michael Klompas, a hospital epidemiologist and infectious disease physician at Brigham and Womens Hospital who did not participate in the study, explains that this may be a function of the way individuals bodies become more efficient at moving large amounts of air. They make their muscles do an enormous amount of work, and they need to support that by giving their muscles enormous amounts of oxygen and helping to clear waste products, he says.

If this gives you pause about your current exercise regimen, keep in mind that not all gyms are alikeand the right policies and set-up can help to keep you safe. For instance, the amount of space per person is essential; large spaces, especially those with high ceilings, give the air more space, says Thomas Allison, director of Cardiopulmonary Exercise Testing Laboratories at the Mayo Clinic. Other things to look for at a gym, says Klompas, are a vaccination requirement, a facility that has professionally measured the air flow and put in place air filters, and, ideally, a testing requirement. In Klompas opinion, masks are potentially helpful, but arent likely to be reliable during workoutslooser masks wont do much during vigorous exercise, and its impractical to expect people to wear N95s while exerting themselves.

The researchers note that factors besides fitness status can also affect how many aerosols people emit. Wackerhage says they are also looking into how factors like body mass index, age, and lung condition play a role.

Ultimately, says Klompas, whether or not you go to a gym comes down to your risk tolerance, and weighing the costs and benefits of going to the gym for you, personally. However, he says, you shouldnt pretend that working out indoors, and around other people, doesnt pose risks. If youre not willing to get COVID dont go, says Klompas. At a time like now, when theres a lot of COVID around, it is a high risk proposition.

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