Which statement accurately describes the clavicular portion of the pectoralis major?

• A. It primarily extends the shoulder.
• B. It primarily flexes the shoulder.
• C. It primarily abducts the shoulder.
• D. It primarily medially rotates the shoulder.

Answer: (B)

The clavicular portion of the pectoralis major is best understood by its line of pull: the upper fibers originate on the clavicle and pull the humerus forward and upward when they contract, which produces shoulder flexion. This is why flexing the shoulder is described as its primary action, especially from a neutral or extended position. The sternal portion, by contrast, is more involved in extending the shoulder from a flexed position and supports adduction and medial rotation, so it’s not the main action of the clavicular fibers. Abduction isn’t a primary action of this muscle portion, since the chest muscles are more about adduction and internal rotation, with initial abduction mainly handled by the deltoid and rotator cuff. Medial rotation occurs as a secondary effect of the chest muscles, but the defining action of the clavicular portion is flexion of the shoulder.