Several months into the coronavirus pandemic, battles over when to wear masks have heated up, sometimes with political alliances replacing health guidelines.

And few activities seem to have incited more debate than exercise: cyclists, runners, skaters — everyone seems to have contradicting interpretations of the science and etiquette around how to work out.

The Centers for Disease Control and Prevention recommends wearing cloth face coverings in public settings “where other social distancing measures are difficult to maintain,” but offers no specific guidance on exercising.

There is no scientific consensus on the importance of wearing a mask while exercising, primarily because so little research has been completed. Researchers do agree that masks slow the spread of the virus. But exercisers also agree that wearing a mask while working out is much more difficult than walking in a mask.

“It’s harder to breathe, and it’s a lot more clammy,” said Gaston Ly, a store manager at Running Room in Honolulu.

When Larry Holt, the owner of Ken Combs Running Store in Louisville, Ky., was asked if the runners who frequent his shop are wearing face masks, he responded: “Oh, gosh no! That’s the craziest thing I’ve ever heard of in my life.”

If a runner, biker or skater were to infect you, it most likely would occur while you were stopped and talking to them, said Julian Tang, a virologist and a professor at the University of Leicester in England. He thinks the risk of infection from quickly passing someone is low, because the “massive air volume will dilute any exhaled virus and the wind may carry it away.”

A study goes viral

But if exercising people are breathing harder, doesn’t that make a mask more important?

In April, a draft of a scientific study by Belgian and Dutch engineers indicated that runners, brisk walkers and cyclists create a wake of air behind them that could carry exhaled respiratory droplets much farther than 6 feet. For a few days, every social media platform seemed to be oozing with the same terrifying graphic: two runners, one spewing a colorful cloud — many interpreted it to be coronavirus — on a man behind him.

The study’s authors soon published a follow-up, noting that their research was just an engineering wind-flow model that found that when we walk or run, the air moves differently around us than when we are still. They warned people not to draw conclusions from their research about how the virus infects people.

One useful takeaway, both the study’s authors and several researchers not involved in it said: It’s best to avoid running or biking directly behind someone for a prolonged period.

Another factor to consider, experts say, is that wearing a mask while exercising can make other people feel more at ease. Douglas Nicaragua, owner of Go Run in Miami, advises runners to take along a mask. If you cross paths with someone, put it on.

“Over time, you’ll get used to it,” said Joey Ta, a competitive endurance athlete in Los Angeles who recently started wearing a mask.

People exercising have used several kinds of masks. A surgical mask can grow damp and heavy with sweat; so can a cloth one. A bandanna tied around the head may slip more easily when running. Some may even consider a face shield. Others have used a face gaiter or Buff, a tube of cloth that extends from the collarbone to the ridge of the nose.

Whether you wear a mask or not, pay attention to the position of people around you, said. Dr. Benjamin Levine, a professor of internal medicine at UT Southwestern Medical Center and Texas Health Presbyterian Dallas and an adviser to the U.S. track and field team.

He urges focusing on what he calls the four D’s: “double the distance” from 6 to 12 feet and “don’t draft,” meaning “don’t run or cycle directly behind someone so you are continually running into and breathing their expired air.”