This article originally appeared in The New York Times on June 17, 2020.

Exercising While Wearing a Mask

Some types of masks are better than others when exercising in crowded spaces.

By Gretchen Reynolds

Wearing a mask during exercise reduces the risk that we will infect someone else with the novel coronavirus if we unwittingly carry the disease. But wearing a mask also affects how the exercise affects us, according to exercise scientists who have begun to look into the effects of covering your face while working out.

Their research and insights, some of them based on self-experimentation, raise practical questions about whether some types of masks might be better than others for exercise, how often masks should be swapped out during prolonged exertions and just how much we should expect our heart rates to soar if we attempt to interval train with a mask on.

Almost all of us know by now that the Centers for Disease Control and Prevention recommends we cover our faces when we are in crowded public spaces, such as parks or pathways, and in shared, indoor locations, including gyms, to help block the transmission of the novel coronavirus through respiration. These recommendations — which are requirements in some communities and businesses — become particularly pressing when we exercise, since past studies show that our breathing rates can double or even quadruple then, sending out higher numbers of potentially infectious respiratory droplets.

But while there is growing evidence that masks can affect breathing in general, as my colleague Jane Brody wrote about this week, little is yet known scientifically about if and how face coverings change the subjective experience and physical impacts of exercise — although many exercisers will tell you that they do. A commentary published this month on the website of the British Journal of Sports Medicine points out that covering your face during exercise “comes with issues of potential breathing restriction and discomfort” and requires “balancing benefits versus possible adverse events.”

To find out more about those benefits and adversities, I contacted several scientists who have begun analyzing masks and exercise, including the primary author of the new commentary. Because university closures and other pandemic restrictions prevent large-scale, lab-based experiments now, these scientists’ research efforts primarily have involved wearing masks themselves during workouts or asking a few close colleagues to do the same and taking copious notes. But although anecdotal and unpublished, their analyses provide useful tips and cautions for mask wearing during workouts.

Perhaps most important, they show that masks do alter exercise, says Cedric X. Bryant, the president and chief science officer of the American Council on Exercise, a nonprofit organization that funds exercise research and certifies fitness professionals. “In my personal experience,” he says, “heart rates are higher at the same relative intensity when you wear a mask.”

In other words, if you don a mask before running or cycling at your usual pace, your heart rate will be more elevated than before. “You should anticipate that it will be about eight to 10 beats higher per minute” when you wear a mask than when you do not, Dr. Bryant says. This exaggerated rise in heart rate will be most pronounced during intense efforts, he says, such as hill repeats or intervals.

Some people also could experience lightheadedness during familiar workouts while masked, says Len Kravitz, a professor of exercise science at the University of New Mexico. He is in the early stages of planning a large study of masks and exercise with funding from A.C.E. that will begin when pandemic restrictions allow, he says.

But already he has conducted an informal experiment with two of his students, both experienced athletes. One ran, masked, without breathing difficulties, he says. The other, wearing the same type of cloth mask, felt dizzy after only a few minutes of exertion.

Thankfully, such discomforts likely can be minimized by judicious mask choice and fitting, says Christa Janse van Rensburg, a professor of exercise science at the University of Pretoria in South Africa, who wrote the commentary about masks with her graduate student, Jessica Hamuy Blanco.

Avoid paper, surgical masks altogether during exercise, she says, since they rapidly become wet when we breathe into them vigorously and lose some of their ability to block outgoing germs. Cotton cloth masks likewise dampen easily. Cloth masks made from breathable, synthetic materials should lessen moisture buildup. Choose models, though, that “have two layers of fabric or less,” she says, to avoid facial overheating and any bunching of the cloth that might constrict breathing.

Some exercisers may prefer neck gaiters (also called buffs), which can be pulled up over the mouth and nose but remain open at the bottom, increasing air flow. “This can be good from a comfort point of view,” Dr. van Rensburg says, “but perhaps with the trade-off of less-effective infection control.” Look for gaiters in summer-weight fabrics, not those designed for use during skiing.

Plan, too, to carry extras of your preferred mask if you will be exercising for more than about 30 minutes, Dr. Bryant says. Even breathable fabrics become drenched at that point and should be replaced. Try not to touch the front of the used mask, since any viral particles you came into contact with could have accumulated there, he says, and after removal, pack or dispose of it carefully.

Some athletic clothing companies, including Under Armour, Koral, Zensah and others have begun to manufacture masks for use during exercise. You may need to try several models to find the one that most comfortably fits your face and exercise routine, Dr. Bryant says.

But do not be deterred in the interim from wearing a mask if you will be exercising around other people, he continues. Wearing a mask can be particularly important if you are exercising indoors at a gym, where air circulation is less likely to dissipate the virus.

“I know some people find them unpleasant” while running or cycling “and there are controversies” about whether they should be mandatory. “But I look on masks as an opportunity to be a good citizen and show that you care about the well-being of others,” he says, even as you bolster your own well-being with a workout.