Probably swallowing air. When you breathe through your mouth it causes it to dry up and then we try to swallow to promote saliva. So she is probably inadvertently swallowing air.
She should try to train herself to breathe through the nose and exhale out the mouth. And if she feels like she isn't getting enough air that way then to use nose strips to help expand the nostrils and also to slow down the pase to build up lung compactly and endurance.
Post Edited (NewShinyCD) : 4/18/2012 10:33:00 PM (GMT-6)