Straining is the voluntary and forceful elevation of abdominal pressure for the purpose of, for example:
It is achieved by the voluntary contraction of the diaphragm and abdominal wall muscles. As the diaphragm is much weaker than the combined effect of the latter group, the glottis can be voluntarily closed to splint the lungs and hence the underlying diaphragm. Escape of air pass the glottis can produce characteristic grunting during excessive straining.
Last reviewed 01/2018