What set of muscles can create spinal extension?

• A. Epaxial
• B. Hypaxial
• C. Abaxial
• D. Transversospinalis

Answer: (A)

Spinal extension is produced by the muscles that run along the back of the spine, the epaxial group. These muscles lie dorsal to the vertebral column and attach along multiple vertebrae, so when both sides contract they pull the vertebrae posteriorly and reinforce an upright or arched spine. This dorsal/epaxial set includes the large back extensors (the erector spinae) and the deeper transversospinalis group, all of which can contribute to extending the spine and stabilizing it during movement.

Hypaxial muscles are located ventrally to the transverse processes and mainly contribute to flexion of the trunk, lateral movements, or respiration, not spinal extension. Abaxial isn’t a primary functional grouping for spinal extension. The transversospinalis is actually part of the epaxial set, and while it assists with extension and stabilization, the broader category capable of producing extension is epaxial.