Diaphragmatic breathing

Diaphragmatic breathing is a form of breathing done by contracting the diaphragm, a muscle located beneath the lungs in the chest cavity. Although the diaphragm contracts during all breathing, usually involuntarily, diaphragmatic breathing is characterized by the expansion of the belly rather than the chest. During diaphragmatic breathing, the diaphragm is contracted downwards far enough that it displaces abdominal organs such as the stomach and upper intestines, causing the stomach to bulge outwards.

Speaking applications
Diaphragmatic breathing is thought to reduce nervousness and increase volume. Exercises aimed at promoting diaphragmatic breathing may be used to reduce breathlessness and other symptoms of poor breathing while speaking. (See speaking drills.)