Variant 1: Neutral grip
Flexion occurs in the shoulder joint, which involves the anterior deltoid, the pectoralis major (upper portion), and the coracobrachialis. In this action the upper arm moves from a position behind the trunk to a position alongside the body. In the shoulder girdle the muscles involved are the pectoralis minor and the rhomboid in downward rotation of the scapulae. In addition, the scapulae move downward in a straight line from the pull of the lower trapezius and pectoralis minor. Extension occurs in the elbow joint, in which the upper arms move up and away from the forearms as the elbows come closer to the body.
Variant 2: Pronated grip
In the shoulder joint the latissimus dorsi, teres major, and lower pectoralis major are involved in adduction. In this action the upper arms move in toward the sides of the body from an up and out to the side position. In the shoulder girdle and elbow joints, the muscles and actions are the same as in Variant 1.