What is the primary action of the pectoralis major muscle?

The primary action of the pectoralis major muscle is shoulder adduction. This muscle plays a crucial role in moving the arm towards the body’s midline, which is the definition of adduction. In addition to this primary action, the pectoralis major also assists in other movements such as shoulder flexion and medial rotation, but its most significant and defining action is indeed adduction. This characteristic makes it an essential muscle for various activities that involve bringing the arms closer to the body, such as reaching across the chest or performing pushing movements. Understanding its primary role in shoulder mechanics is vital for assessing and developing training regimens, particularly in strength training and rehabilitation contexts.