Which muscle primarily flexes the spinal column?

Which muscle primarily flexes the spinal column?

• A. Rectus Abdominis
• B. External Oblique
• C. Internal Oblique
• D. Transversus Abdominis

Answer: (A)

Flexing the spinal column means bending the trunk forward. The rectus abdominis sits on the front of the abdomen and, when it contracts, it pulls the rib cage toward the pelvis, producing trunk flexion. Its straight, vertical fibers are well positioned to create pure flexion, which is why it’s the primary spinal flexor. The external and internal obliques can also contribute to flexion when both sides contract, but their oblique fiber directions mean they also help with rotation and lateral bending rather than acting as the main flexors. The transversus abdominis lies deepest with horizontal fibers and mainly stabilizes the trunk and increases intra-abdominal pressure rather than flexing the spine.

Flexing the spinal column means bending the trunk forward. The rectus abdominis sits on the front of the abdomen and, when it contracts, it pulls the rib cage toward the pelvis, producing trunk flexion. Its straight, vertical fibers are well positioned to create pure flexion, which is why it’s the primary spinal flexor.

The external and internal obliques can also contribute to flexion when both sides contract, but their oblique fiber directions mean they also help with rotation and lateral bending rather than acting as the main flexors. The transversus abdominis lies deepest with horizontal fibers and mainly stabilizes the trunk and increases intra-abdominal pressure rather than flexing the spine.