Place your hands palm down on your stomach at the base of the rib cage. What fills them deeper is the pushing down of the diaphragm. The diaphragm creates a suction which draws air into the lungs. In this process, the life-giving oxygen fills the lungs and gets into the blood stream for distribution to the cells. Lay the palms of your hands on your stomach just below the rib cage, middle fingers barely touching each other, and take a slow deep breath.
Chest breathing fills the middle and upper parts of the lungs.
Belly breathing is the most efficient method. Infants and small children use only this method until the chest matures. The yoga breath or roll breathing combines belly and chest breathing. Keep making that humming sound as long as possible. Three short inhales are done through the nose without exhaling.