External oblique muscle
It is the outermost muscle located on both sides of the trunk. The muscle fibers lie beneath the thoracic (chest) and abdominal skin originating from the lower ribs to the pelvis (hip bone). The muscular part makes up the lateral part of the abdominal wall. The muscle contributes to the variety of trunk movements and is mainly responsible for performing functions, such as twisting the sides of the trunk, pulling the chest downwards, rotating the spine. Any form of strain, injury, or trauma to the muscle can be debilitating.
Functions of the external oblique muscle:
The external abdominal oblique muscle has a variety of functions depending on whether it contracts unilaterally (one side) or bilaterally (both sides). When acting unilaterally and in synergy with the internal oblique muscle, it rotates the trunk to the opposite side. When working together with back muscles, it contributes to bending of the trunk sideways. When contracting on both sides, it leads to the forward flexion (forward bending) of the trunk. This activity also increases the tone of the abdominal wall and positive intra-abdominal pressure, which is part of various physiological processes, such as forced exhalation, defecation (passing stools), micturition (urinating), and labor (childbirth).