How do the Inspiratory muscles contribute to the breathing process?
The diaphragm and chest wall muscles act together like a bellows to pump air in and out of the chest. To breathe in these muscles contract to expand the chest cavity, causing a pressure drop into which the air flows. To breathe out, you simply relax these ‘inspiratory’ muscles and the chest springs back forcing the air out of your lungs. During exercise the exhalation is assisted by contraction of the abdominal muscles. Thus, the inspiratory muscles undertake most of the work of breathing. In contrast to our frequent observations of inspiratory muscle fatigue, our research has never identified exercise-induced expiratory muscle fatigue. For this reason we’ve found it unnecessary to train anything other then the inspiratory muscles. At rest you breathe around 12 litres of air per minute, but during heavy exercise this can rise to over 150 litres per minute, and in elite athletes, this can be as high as 220 litres.
