Which muscle would primarily be engaged during an overhead arm lift?

When performing an overhead arm lift, the trapezius muscle plays a crucial role in stabilizing and moving the shoulder girdle. The trapezius is a large, triangular muscle that spans the back of the neck down to the middle of the back, and is responsible for actions such as elevation, retraction, and rotation of the scapula.

During an overhead lift, the upper fibers of the trapezius assist in elevating the scapula, allowing the arm to move upward effectively. Moreover, the trapezius is essential for maintaining proper posture and stability of the shoulder joint while lifting, ensuring that the movement is smooth and controlled.

Other muscles, like the serratus anterior, do support shoulder function and help in protracting the scapula, but the primary engagement during an overhead arm lift mainly involves the trapezius due to its direct role in elevating and stabilizing the shoulder girdle throughout the movement. Meanwhile, the rhomboid minor and psoas major are not predominantly active in this specific action, as their functions relate to retraction of the scapula and hip flexion, respectively.