Final answer:
The four other medial rotators of the arm besides the subscapularis muscle are the deltoid, teres major, pectoralis major, and the latissimus dorsi. They all contribute to medial rotation but additionally have other roles in shoulder and arm movement.
Step-by-step explanation:
Besides the subscapularis muscle, there are four other muscles that act as medial rotators of the arm. These muscles include the deltoid, teres major, pectoralis major, and the latissimus dorsi. Although each of these muscles has multiple actions depending on the motion of the arm and shoulder joint, they all contribute to the medial rotation of the humerus.
The deltoid is known primarily as the major abductor of the arm, but it also plays a role in medially rotating the arm. The teres major assists in adduction and medial rotation of the arm. The pectoralis major and the latissimus dorsi both also contribute to medial rotation of the arm.