Which of the following muscles contributes to external rotation of the shoulder?

The infraspinatus is primarily responsible for the external rotation of the shoulder. It is one of the four rotator cuff muscles, which play a crucial role in stabilizing the shoulder joint and facilitating its movement. The infraspinatus originates from the infraspinous fossa of the scapula and inserts into the greater tubercle of the humerus. When it contracts, it pulls the humerus in a lateral direction, effectively rotating it outward.

The subscapularis, on the other hand, is involved in internal rotation, while the supraspinatus assists in shoulder abduction but not specifically in external rotation. The teres major, though it plays a role in shoulder adduction and internal rotation, does not contribute to external rotation. Thus, the infraspinatus is the muscle specifically identified for its primary function in externally rotating the shoulder.