What set of muscles create spinal flexion?

• A. Epaxial
• B. Hypaxial
• C. Axial
• D. Serratus anterior

Answer: (B)

Spinal flexion is produced by the hypaxial muscles, the ventral trunk group that lies along the front and sides of the torso. These include the rectus abdominis, external and internal obliques, and transversus abdominis. When they contract, they shorten the front of the trunk, pulling the rib cage toward the pelvis and bending the spine forward while often increasing intra-abdominal pressure. Epaxial muscles, located along the back, primarily extend the spine (and can assist with lateral movements) rather than flex it. Serratus anterior acts on the shoulder girdle and does not help bend the spine. The term axial is too broad to specify a distinct set for spinal flexion.