Masks should not be worn during "vigorous intensity physical activity," according to controversial guidance the World Health Organization released Tuesday.
As such, WHO said "people should not wear masks during vigorous intensity physical activity because masks may reduce the ability to breathe comfortably."
One small study, for instance, showed that healthy exercisers' blood and muscle oxygen levels weren't affected when performing the same fitness test with a cloth mask, medical mask, and no mask.
In places with "known or sporadic" transmission, healthcare workers should wear medical masks when patients are present, the WHO said.
Caregivers or housemates of suspected or confirmed COVID-19 should also wear medical masks when in the same room.
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World Health Organization, WHO, Brown University