For shoulder abduction, which muscles are listed as antagonists?

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

Answer: (B)

Shoulder abduction is resisted by muscles that pull the arm toward the midline or rotate it in a way that reduces upward lifting. Latissimus dorsi and pectoralis major are strong adductors and internal rotators of the humerus, so their action counters the upward, outward pull of the abductors. The long head of the triceps crosses the shoulder and can extend and adduct the arm, which also opposes the abductive movement, especially when the arm is raised. The infraspinatus and teres minor are external rotators and help stabilize the shoulder, countering internal-rotation components that accompany some abductive actions, thereby providing antagonistic control in this range. Together, these muscles oppose shoulder abduction, aligning with how they function to draw the arm back toward the body or stabilize it against the abducting effort.