Which muscles act as primary agonists for shoulder adduction?

• A. Pectoralis Major, Latissimus Dorsi, Triceps Brachii, Infraspinatus, Teres Minor
• B. Supraspinatus, Deltoid
• C. Deltoid (Anterior), Pectoralis Major
• D. Subscapularis, Latissimus Dorsi

Answer: (A)

Shoulder adduction is driven mainly by muscles that pull the humerus toward the body. The primary agonists are the pectoralis major, latissimus dorsi, and teres major. These three provide the strongest inward pull across a range of arm positions, making them the main movers for bringing the arm down toward the midline. The deltoid, supraspinatus, and other muscles listed mostly contribute to abduction, stabilization, or external rotation rather than primary adduction. The subscapularis helps with internal rotation and stabilization, and the triceps long head can assist in adduction only in certain positions, but it is not considered a primary adductor. So, the key idea is that the main players for shoulder adduction are pectoralis major, latissimus dorsi, and teres major, with the others not serving as primary movers in this action.