Which action is primarily produced by contraction of the erector spinae muscle group?

• A. Protraction of the scapula
• B. Flexion of the vertebral column
• C. Extension of the knee
• D. Extension of the vertebral column (and head/neck when acting bilaterally)

Answer: (D)

Verified step by step guidance

1. Identify the anatomical location and function of the erector spinae muscle group. This group runs longitudinally along the vertebral column and is primarily responsible for movements of the spine and head.
2. Understand the types of movements possible at the vertebral column: flexion (bending forward), extension (bending backward), lateral flexion (side bending), and rotation.
3. Recall that muscle contraction typically produces movement by pulling on bones or structures. The erector spinae muscles, when contracting bilaterally (both sides together), pull the vertebral column into extension, which means bending backward.
4. Compare the given options: protraction of the scapula involves muscles like the serratus anterior, flexion of the vertebral column involves muscles like the rectus abdominis, and extension of the knee involves muscles like the quadriceps femoris. None of these are primarily actions of the erector spinae.
5. Conclude that the primary action of the erector spinae muscle group is extension of the vertebral column (and head/neck when acting bilaterally), which aligns with the correct answer.