Watch out Your breathing Pattern!
Most people have wrong believes or facts about their breathing mechanics e.g. they think that exhaling needs more effort than inhaling, and many people who have issues with public speaking or who stutters develop irregular breathing habits, such as shallow breathing, holding or forcing their breath, or beginning speech with exerting effort and building up air pressure!
Therefore, an important part to overcome these habits is to establish a proper breathing pattern for speech.
Q: Do you think exhaling needs more effort than inhaling?
If your answer is YES. You have a WRONG fact! Here it is the mechanics of breathing...
Almost all the physical effort in breathing happens when you inhale. You contract your dome-shaped diaphragm, causing it to flatten out and enlarge your chest cavity. This temporarily compresses your abdominal cavity, causing the front of your abdomen to bulge out. meanwhile, certain chest muscles also contract to raise your rib cage. As your chest cavity gets larger, your lungs expand and suck in air. To release the air, all you have to do is relax!
From Book: Understanding and controlling stuttering By William D.Parry, J.D., M.A, CCC-SLP