What is the primary action of the pectoralis major?

The primary action of the pectoralis major is adduction and flexion of the arm. This muscle is a large, fan-shaped muscle located in the upper chest, and it plays a critical role in upper body movements.

During adduction, the pectoralis major draws the arm closer to the body’s midline. This is particularly evident in movements like bringing the arms together in front of the torso. In terms of flexion, the muscle assists in lifting the arm forward and upward, especially when the arm starts from a position at the side of the body. For example, during actions like lifting a weight or performing a push-up, the pectoralis major engages to move the arms upwards and towards the body’s center.

Understanding this muscle's function is vital in any training or rehabilitation context, as it directly influences performance in various activities and exercises that involve the upper body. Moreover, emphasizing this muscle's adduction and flexion capabilities aids in identifying potential weaknesses or imbalances in upper body strength and movement patterns.