The simple act of breathing provides plenty of information about the general use of the body. Breathing involves a complex interaction between muscles, ribcage and lungs. In natural balance the ribs move out and up, creating a vacuum in the lung to let a fresh breathe in.
At the lower end of the ribcage, the diaphragm moves down, allowing a three dimensional expansion of the lungs. In a balanced state breathing just happens, the outbreath exposing more activity than the inbreath. The muscles, that hinged the ribcage apart and pulled the diaphragm into an arc, and can push the carbon dioxide oxygen mixture out of the lungs, simply by returning into their natural tonal state.
Breathing involves more than half of the space spanned by the trunk, and many muscles can constrict the movement of the ribcage. However, coordination of head, neck and back allows the ribcage to move freely, the shoulder girdle and the scapula gliding on it.
The most efficient way of breathing differs for every person, we gain an easier breath rather by removing unnecessary obstacles than doing it right.