Which muscle is the primary mover in shoulder extension and adduction?

Which muscle is the primary mover in shoulder extension and adduction?

• A. Latissimus Dorsi
• B. Serratus Anterior
• C. Subscapularis
• D. Supraspinatus

Answer: (A)

Shoulder extension and adduction require pulling the upper arm backward and toward the body. The latissimus dorsi is the strongest muscle for both actions, with a broad attachment from the lower back and pelvis to the humerus. Its line of pull directs the arm downward and backward, producing extension, and toward the midline to create adduction, especially when the arm is away from the body. While other muscles have related roles—serratus anterior stabilizes the scapula, subscapularis handles internal rotation and joint stability, and supraspinatus initiates abduction—the latissimus dorsi is the primary mover for extending and adducting the shoulder.

Shoulder extension and adduction require pulling the upper arm backward and toward the body. The latissimus dorsi is the strongest muscle for both actions, with a broad attachment from the lower back and pelvis to the humerus. Its line of pull directs the arm downward and backward, producing extension, and toward the midline to create adduction, especially when the arm is away from the body. While other muscles have related roles—serratus anterior stabilizes the scapula, subscapularis handles internal rotation and joint stability, and supraspinatus initiates abduction—the latissimus dorsi is the primary mover for extending and adducting the shoulder.