The rotator cuff, explained
Surrounding the glenohumeral joint is the rotator cuff, a group of four muscles that help negotiate the position of the humeral head within its socket. These muscles originate from different landmarks on the scapula and latch onto the head of the humerus. They are:
SUBSCAPULARIS (NOT SHOWN) Located on the front side of the scapula; helps you internally rotate the arm
SUPRASPINATUS Located on the top side of the scapula; initiates abduction, or the lifting of your arm out to the side
INFRASPINATUS The bigger muscle on the back surface of the scapula; externally rotates the arm bone and stabilizes the shoulder joint
TERES MINOR The smaller muscle on the back surface of the scapula; externally rotates the shoulder
To keep the rotator cuff muscles injury-free, it’s crucial to stabilize the entire shoulder girdle when you place weight on your hands—like in Plank Pose, for example. In an efficient Plank, the body recruits multiple muscles to stabilize the shoulder girdle. Two key muscles that stabilize the scapulae against your rib cage at the ScC joints are the serratus anterior muscles (which protract the shoulder blades, pulling them away from the spine) and the rhomboids (which retract the shoulder blades, pulling them toward the spine). While the serratus anterior and rhomboids have opposing actions, they work together to help keep your scapulae from winging off your back and wreaking havoc on the rest of your shoulder joints and muscles.