Full External Abdominal Oblique Muscle Description
[Continued from above] . . .
The external abdominal obliques have their origins along the lateral ribs 5 through 12 and insert into the linea alba of the abdomen, the pubis, and the iliac crest of the hip bones. Their shape is roughly rectangular with the long axis running anterior to posterior along the linea alba. Muscle fibers in the external obliques run medially and inferiorly from the origins to the insertions across the lateral sides of the abdomen and end just lateral to the rectus abdominis muscles.
The location and structure of the external abdominal obliques gives them many different possible actions. Contraction of both external obliques together results in the compression of the abdomen (as in sucking in the gut) or the flexion of the trunk (as in performing a crunch or sit-up). Contraction of one of the abdominal obliques results in the lateral flexion and rotation of the trunk on the opposite side; in other words, the left external oblique rotates and flexes the trunk to the right.
Prepared by Tim Taylor, Anatomy and Physiology Instructor