Karin, this is how is done, you pinch your nose with your fingers and don’t let any air out and at the same time you are trying to exhale out of your mouth but, dont let any air out of the mouth either, do it for 10 reps. Again the puropose is to try to exhale through your nose and mouth at the same time, but you don’t. I hope that explains it? This technique is a Physical Therapy Technique, and also works great after any impact that causes you to lose your breath. Also, it will get rid of a stich on your side, instantly.
Kelli, why you get a “side stich” is one question? As you know it could be many reasons. My answer is if you do get them, you can get rid of it in seconds, how? Perform an Isometric contraction of your diaphragm, and if you perform this exercise before you run, you probably wont get a “side stich”, good luck.