Masks Do Not Impair Oxygen Intake During Workouts, Studies Suggest

Wearing a mask on a run or bike ride may not feel good, but it does good. Two studies and one review all came to the same conclusion: Masks do not restrict a healthy person’s flow of oxygen or impair lung function during vigorous exercise. It does, however, limit the spread of viral respiratory droplets responsible for the global pandemic.

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Prior to these studies, little research has explored how masks affect our workouts. We all have our own opinion about how running with a mask feels but what’s the empirical evidence? To find out, scientists had participants ride to exhaustion on a stationary bike while donning various masks.

The first study published in the Scandinavian Journal of Medicine and Science in Sports studied 16 healthy adult men as they rode a stationary bike while their blood pressure, heart rate, respiratory rate, blood pressure, oxygen saturation, and time to exhaustion were measured. Each participant served as his own control and performed the test three times: once without a face mask, once with a surgical mask, and once wearing an N95 respirator.

There were few differences in the men’s measurements. The only significant effect was slightly increased levels of carbon dioxide in their breath while wearing N95 masks. The researchers recommend masks stay on during exercise, though perhaps leave the N95s for health care workers.

The second study published this month in the International Journal of Environmental Research and Public Health recruited 14 healthy men and women, who similarly performed ride-to-exhaustion tests. They wore either a three-layer cloth face mask, a disposable surgical face mask, or no mask on three separate occasions. There were no significant differences in physiological measures.

Their findings “indicate that people can wear face masks during intense exercise with no detrimental effects on performance and minimal impact on blood and muscle oxygenation," write the researchers. "This is important when fitness centers open up during Covid-19 since respiratory droplets may be propelled further with heavy breathing during vigorous exercise and because of reports of Covid-19 clusters in crowded enclosed exercise facilities.”

A third study published this week in the Annals of the American Thoracic Society reviewed the literature and found no evidence to suggest lung function decreases during heavy exercise with a mask. However, the perception of difficult breathing may increase, even though there are no physiological signs to support less oxygen flow.

"The major finding is that masks increase dyspnea, which is the unpleasant sensation of being aware of breathing. Masks make your face hot and this is one possible explanation for the increase in dyspnea. However this subjective feeling is not because of measurable changes in physiology as mentioned above," first author Susan Hopkins, MD, PhD, professor of medicine and radiology at University of California San Diego School of Medicine, told IFLScience.

"Studies that have evaluated the effects of N95, cloth or surgical masks on blood oxygenation or CO2 levels during exercise have either found no effect or very small effects (1-2 percent change) that are inconsequential for normal people. Even for patients with cardiopulmonary disease the changes are small."

The first two studies included healthy adults and were relatively small, which means the results may differ for those who are old, young, or who have pre-existing conditions. The review study, however, did not find a difference for young and old populations, except for the very young (less than 2 years) and masks are not recommended for them anyway. Similarly, those with pre-existing conditions did not have many physiological changes, although they may have more dyspnea.

"They should talk to their doctors if they have concerns, and since they are at very high risk if they get Covid they really need to consider if they need to be out in the community without a mask," said Hopkins.

The studies also studied cycling so whether or not the outcomes are similar for running and gym workouts remains to be seen, though the researchers say it’s likely.

"For people who find wearing a mask unpleasant, changing the type of mask (i.e. from cloth to disposable) or starting slowly with light exercise and wearing it for shorter periods of time (while staying away from other people outdoors), until they get used to the sensation of wearing a mask, may help," said Hopkins.

All this is to say: please wear a mask.

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