When I run at a fast pace, it is hard to breathe. I inhale through my nose deeply, and out with my mouth, but I still have a hard time breathing. One of the things that has helped me, though, is using good posture when running. Anything else I can do?
Breathe through both your nose and your mouth. There is no added benefit to only breathing through your nose. Good posture does help so your lungs can expand and contract properly, but you should get your oxygen quicker by using both your mouth and nose.
Breathing in through your nose doesn't help you prevent cramps or help you run more efficiently. Watch the video below for a more detailed explanation.