Which is an action of the rectus abdominis?

• A. Flex the vertebral column
• B. Compress abdominal contents
• C. Rotate head and neck to the same side
• D. Elevate the ribs

Answer: (A)

The rectus abdominis is the vertically running muscle of the front abdomen, and its primary job is to bend the trunk. When it contracts, it pulls the rib cage and pelvis closer together, producing flexion of the vertebral column and a forward bend of the torso. This direct movement on the spine is the clearest, defining action of this muscle. It can also help press the abdominal contents inward to increase intra-abdominal pressure, which is useful in tasks like forced expiration, but it does not rotate the head and neck or elevate the ribs—those actions are performed by other muscles.