The external oblique muscle is one of the largest parts of the trunk area. Each side of the body has an external oblique muscle.
The external oblique muscle is one of the outermost abdominal muscles, extending from the lower half of the ribs around and down to the pelvis. Its lowest part connects to the the top corner of the pelvis (called the crest of the ilium), the bottom-front of the pelvis (the pubis), and the linea alba, a band of fibers that runs vertically along the inside of the abdominal wall. Together, the external oblique muscles cover the sides of the abdominal area. The intercostal and subcostal nerves connect the external oblique muscles to the brain.
The external obliques on either side not only help rotate the trunk, but they perform a few other vital functions. These muscles help pull the chest, as a whole, downwards, which compresses the abdominal cavity. Although relatively minor in scope, the external oblique muscle also supports the rotation of the spine.
Since the muscle contributes to a variety of trunk movements, strain or injury to the muscle can be debilitating. This may include movements that do not directly use the muscle. For example, ambulatory motions such as walking or running, which cause slight movements in the torso.