The diaphragm is a major muscle used in breathing and is located beneath the lowest two ribs. At rest, the diaphragm muscle is bell shaped. During inspiration, it lowers and flattens out.
Optimizing the use of the diaphragm is beneficial because it pulls air into the lower lobes of the lungs where more gas exchange takes place. Not only is the diaphragm the most efficient of all respiratory muscles, but using it tends to be very relaxing and calming.
Along with our diaphragm, we use intercostal and abdominal muscles in the work of breathing. The intercostals (muscles between the ribs) pull to lift the rib cage up and out. This causes the lungs to open in all directions and air can be pulled down the airways. To exhale, the muscles that have been pulling relax and air is forced out.
The diaphragm tenses, pulling air in; and relaxes, letting the spring of the ribs push the air out again.
This information has been approved by Shelby Jenkins, OTR and Chelsea Randall, MS, OTR/L (May 2012).