What is the primary muscle responsible for shoulder adduction?

The primary muscle responsible for shoulder adduction is the latissimus dorsi. This muscle plays a significant role in pulling the arm down and back toward the body. It is a large, broad muscle located primarily in the back but extends to the sides, making it highly effective in activities that involve drawing the arms closer to the torso.

Shoulder adduction occurs when the humerus is moved toward the midline of the body, and the latissimus dorsi is particularly effective at this movement due to its anatomical position and orientation of muscle fibers. It aids in movements such as pulling or reaching downward, making it crucial for various upper body activities, including swimming, rowing, and climbing.

While other muscles listed contribute to shoulder movements, their primary functions do not directly emphasize adduction as strongly as the latissimus dorsi. The trapezius assists with scapular movement and stabilization, the deltoid is primarily involved in arm abduction and flexion, and the rhomboid major mainly focuses on retracting the scapula rather than adducting the arm.