Many different muscles are used in breathing.
The largest and most efficient muscle is the diaphragm. The diaphragm is a large muscle that lies under the lungs and separates them from the organs below.
As the diaphragm moves down or flattens, the ribs flare outward, the lungs expand and air is drawn in. This process is called inhalation or inspiration. As the diaphragm relaxes, air leaves the lungs and they spring back into their original position. This is called exhalation or expiration.
The lungs, like balloons, require energy to blow up but no energy is needed to get air out.
The other muscles used in breathing can be found between the ribs and between the neck and the upper ribs. The diaphragm, muscles between the ribs and one of the muscles in the neck, called the scalene muscle, are involved in almost every breath we take. If we need more help expanding our lungs, we “recruit” other muscles in the neck and shoulders.
When muscles don’t work
In some conditions, such as emphysema, the diaphragm is pushed down so that it doesn’t work properly. This means that the other muscles must work extra hard because they aren’t as efficient as the diaphragm. When this happens, patients may experience breathlessness or shortness of breath.