What action does the anterior deltoid perform?

The anterior deltoid is primarily responsible for flexion and horizontal adduction of the humerus at the shoulder joint. This muscle is located at the front of the shoulder, and when activated, it helps raise the arm forward (flexion) and assists in bringing the arm across the front of the body (horizontal adduction). This action is crucial during movements such as lifting the arms forward or when performing exercises like front raises or chest flies.

While extension and horizontal adduction, abduction, and pulling arms down involve different muscle groups and motions, the anterior deltoid's specific function focuses on flexion and horizontal adduction, making that choice the most accurate representation of its role. Understanding these muscle actions is essential for designing effective exercise programs and ensuring proper technique in various movements.