Breathing and its continuous movement that functions as a kind of hydraulic mechanism, with the rise and fall of the diaphragm on the abdominal viscera, also contributes to the overall balance of the body, exerting some pressure from the inside of the rib cage.
Inspiration is an active mechanism muscularly rather shortens the muscles due to contraction. Exhaling, however, it's done with no contractions, the muscles relax and loosen up, at the same time favored by gravity.
This naturally loose, the letting go, just who practices leading to an open and receptive attitude. It's like learning to empty expressly and then get better. The more empty the air, then draws wider, which also earns lung capacity, thereby increasing oxygen supply.