Which muscles are involved in horizontal adduction at the shoulder?

Horizontal adduction at the shoulder primarily involves the anterior deltoid and pectoralis major muscles. The anterior deltoid is responsible for flexing and aiding in adduction of the arm when it is in a horizontal position. Similarly, the pectoralis major, especially its clavicular head, contributes significantly to the horizontal adduction of the shoulder by pulling the arm toward the midline of the body.

The synergistic action of these two muscles allows for effective movement during activities such as reaching across the body or performing exercises that require bringing the arms together in front of the chest. Understanding the function and role of these muscles is crucial for both assessing shoulder motion and developing effective rehabilitation or strength-training programs for the upper extremities.