Imagine yourself exercising: running, hiking, dancing, lifting weights — whatever you like to do. Picture yourself pushing to a maximum intensity. Now, ask yourself: Are you breathing out of your nose or mouth?
If you are like most exercisers, you breathe through your mouth, especially as the intensity of the exercise mounts. But experts are learning that breathing through the mouth may not be as efficient or effective as breathing through the nose.
Source: Why you should use nasal breathing when you exercise
My Comments: Pretty interesting piece.