By, Sean Light CSCS
The subscapularis is the only muscle of the four rotator cuff muscles on the anterior side of the scapula. Along with basic stabilization of the glenohumeral joint, it also has a large role in internally rotating the arm.
For more information on general movements of the shoulder, read my article on the BIOMECHANICS OF BASEBALL PITCHING.
The subscapularis originates on the subscapular fossa, which is a small cavity on the anterior lateral portion of the scapula.
Contracting towards the origin is the point of insertion at the lesser tubercle of the humerus located just inferior to the humeral head.
It’s important to understand that the muscles of the rotator cuff will insert on the top of the humerus and pull the humerus medially thus stabilizing the shoulder.
SOURCE: Hosford DPT, Darryl, “Shoulder Girdle Musculature,” http://www.PTCentral.com/muscles