Which muscle is responsible for scapula retraction?

The trapezius is a large, kite-shaped muscle that spans the upper back and neck. It plays a critical role in various movements of the scapula, including retraction, which refers to pulling the scapulae towards the spine. This action is particularly important for stabilizing the shoulder girdle during arm movements.

The upper fibers of the trapezius elevate the scapula, the middle fibers retract it, and the lower fibers assist in depression and upward rotation. When the middle fibres contract, they pull the scapula medially, effectively retracting it. This retraction is essential for maintaining proper posture and for movements that require the shoulders to move back, such as pulling actions and rowing.

In contrast, while other muscles mentioned have roles involving the scapula, they do not primarily focus on the retraction of the scapula. The latissimus dorsi mainly aids in the adduction and internal rotation of the arm, the levator scapulae elevates the scapula, and the rhomboids also contribute to retraction but are not as prominent or powerful as the trapezius in this specific movement. Thus, the trapezius is the most significant muscle responsible for scapula retraction.