When working out I sometimes do an hour-long stint of swimming—50 meters underwater every three minutes. It takes about a minute to swim one lap underwater, and when I come up for air I take a few quick breaths through my mouth, but after no more than about five seconds, I’ll be breathing through my nose again. Then, after about two minutes of rest, I swim another 50 meters underwater.

What I have noticed is that there is a clear difference: I recover much faster during the two minute rest when I practice nasal breathing as soon as possible after the underwater stint.