Re: What is the best way to breathe while running?

Breathing in through the nostrils and out through the mouth is healthier 
since the air has a chance to be filtered as well as warmed and 
moisturized.  This is especially important in cold weather for people with 
asthma.

However, when the demand for air increases at high levels of exercise there 
is too much resistance in nose breathing for adequate oxygen supply.  In 
the case of extended running it is best to use mouth breathing.  When 
running in cold weather it is best to wear a mask or scarf over the nose 
and mouth so the air can be somewhat properly warmed before getting to the 
lungs.