Breathe in through your nose, out through your mouth. Why?

castell5

Does anyone know why it is commonly said to breathe in through your nose and out through your mouth when working out?
I think, it is meant to control your breathing, but I find it is hard to do that and was always curious what the exact reason is.
Let's hear some shout outs.

daylily2005

I've always heard to do this in cold weather as it helps to give the air a little more time to acclimate to your body temperature (or at least closer) before it hits your lungs. Sounds real, but could be pseudo-science. I just breathe however it feels comfortable.

scottdeeby

I can't do it. Noseholes are too small and I can't get enuff air.

Azdak

In order to keep up with the metabolic demands of running, you have to be able to move as much air in and out of the lungs as possible. At very slow running speeds it might be possible to do that via nasal breathing. However, at some point you can no longer bring in enough air that way and you must breath in with both nose and mouth.

It is more important to stay relaxed -- both with breathing and with your upper-body carriage in general-- than to engage in any sort of manipulated breathing pattern.

scottdeeby

On a more serious note.....when I used to train with a heart rate monitor, I characterized Zone 2 as the "able to breathe through the nose" exertion level. If during the workout I realized that I was breathing through my mouth, I'd slipped into zone 3 (higher exertion) as confirmed on the HRM.

neandermagnon

I've always heard to do this in cold weather as it helps to give the air a little more time to acclimate to your body temperature (or at least closer) before it hits your lungs. Sounds real, but could be pseudo-science. I just breathe however it feels comfortable.

it's not pseudoscience, the nose humidifies dry air slightly, and this is more gentle on the lungs. People who live in colder or drier climates tend to have bigger noses because of it, bigger nose = greater humidifying effect (think Arabs in the desert, or northern Europeans in the cold). I don't know how much research there is from physiologists, but anthropologists refer to this.

That said, if you're really breathless, you don't need to follow this advice, it's more important to get enough air in your lungs when you're out of breath, and the mouth is bigger than the nostrils. Unless you're living in a extremely cold or extremely dry climate, or you have very sensitive lungs it probably won't make a lot of difference. It's probably more useful to apply this advice if you're going for a walk on a snowy day than if you're working out at a moderate temperature and humidity.