Nasal breathing is generally preferable to mouth breathing during low-intensity activities as it may reduce the risk of infection entry.

“And if you're doing, say a zone two cardio, low level cardio, or you're just walking along, it's very clear based on a growing amount of data that being a nasal breather is better than being a mouth breather. And there are a number of different reasons for that we've talked about on the podcast and elsewhere. But one of the additional reasons is a main site of entry for infections is through the mouth.”