Which muscle is the prime mover for Shoulder Abduction?

Which muscle is the prime mover for Shoulder Abduction?

• A. Middle Deltoid
• B. Supraspinatus
• C. Anterior Deltoid
• D. Infraspinatus

Answer: (A)

Shoulder abduction is driven primarily by the middle portion of the deltoid. It provides the bulk of the upward lift once the arm moves away from the body, especially after the initial phase. Supraspinatus plays a crucial role at the start, initiating the first ~15 degrees of abduction and helping stabilize the humeral head, but it does not carry the movement through the majority of the range. The anterior deltoid mainly aids flexion and forward movement rather than pure abduction, and the infraspinatus is more about external rotation and joint stability. So the middle deltoid is the main mover for lifting the arm out to the side.

Shoulder abduction is driven primarily by the middle portion of the deltoid. It provides the bulk of the upward lift once the arm moves away from the body, especially after the initial phase. Supraspinatus plays a crucial role at the start, initiating the first ~15 degrees of abduction and helping stabilize the humeral head, but it does not carry the movement through the majority of the range. The anterior deltoid mainly aids flexion and forward movement rather than pure abduction, and the infraspinatus is more about external rotation and joint stability. So the middle deltoid is the main mover for lifting the arm out to the side.