When the abdomen is struck, a large difference in pressure occurs across the diaphragm. The diaphragm then stretches, which also stretches the diaphragm’s nerves. The resulting mechanical force puts the diaphragm into a muscle spasm, comparable to having a charley horse in the leg. It takes a few seconds for the diaphragm to relax again before breathing can resume normally. Martial artists are often taught to breathe out heavily when struck in the stomach, to minimize this effect.

Often the laryngial muscles contract during diaphragm spasm producing an inspiratory sound known as stridor which can be heard for several cycles as breathing resumes. Singultus, commonly known as the hiccups, is also a form of diaphragm spasm, although much milder. A singultus episode impairs voluntary breathing control for brief moments (measured in milliseconds) rather than for several seconds.

IRiSh