Abdominal Press

a group of muscles that constitute the abdominal wall. The principal muscles of the abdominal press are the abdominal muscles: the external and internal musculi obliqui, the musculi transversi, the musculi recti, and the pyramidal muscles. The muscles of the abdominal press are used in respiration, contracting with expiration; when they contract, the pressure inside the abdomen increases, which facilitates evacuation of the contents of the rectum, urinary bladder, and uterus. Contraction of the muscles of the abdominal press is especially strong during childbirth (labor pains).