While the process of breathing seems like something simple, and something that requires no thought, in singing, proper breathing requires strong muscles and good control.
The first step in the breathing process starts with the brain. The brain sends a message to the diaphragm, telling it to move. The diaphragm is a large dome shaped muscle that divides the chest cavity from the abdominal cavity and attaches to the ribs at the sides and the sternum in the front of the body. When the brain tells the diaphragm to move, it flattens out, enlarging the thorax of the body, the ribs, and the chest. When the chest expands, it pulls on the lungs, causing a drop in pressure in the lungs compared to the pressure of the atmosphere and air is sucked into the lungs to balance the pressures.
There are many muscles used in the process of inhalation. The diaphragm is the most important. The external intercostals are on the outside of the ribs, and extend from rib to rib, in between. These muscles help to pull the lower ribs up when the chest is rising to take air into the lungs. The levatores costorum are small muscles that extend from the vertebrae to the ribs. They also aid in lifting the ribs upward. The serratus posterior superior extend down and out from the vertebrae to the upper ribs in the back. These muscles also help raise the chest. The pectoralis major is the upper chest muscle that fans out from the humerus and inserts into the sternum and the clavicle. The pectoralis minor extends from the scapula and inserts into the second through fifth ribs. This muscle is also fan shaped and helps to raise the ribs. The lattissimus dorsi (or “latts”) is the large muscle on the back extending from the lower vertebrae to the hip bone and from the ribs to the upper arm. This muscle helps to expand the lower part of the thorax. The sternocleidomastoid extends from the skull to the sternum and clavicle. It helps to pull the chest...