The major muscles that line and support the shoulder blade include the infraspinatus, supraspinatus, subscapularis and teres minor. These muscles are commonly referred to as the rotator cuff or, simply, the upper back muscles. To work these muscles most effectively, choose compound exercises, or those that build on one another and/or emphasize more than one muscle group at one time.
External and internal shoulder rotations work the muscles that line the back and front of the shoulder blade, or the infraspinatus and subscapularis, respectively. You can perform these exercises with a dumbbell, lying on your side, seated or standing at a cable machine. The main goal of this exercise is to use your shoulder blade to "rotate" your forearm with your elbow bent at a 90-degree angle, pinned to your side. To perform the external rotation with a low pulley cable, sit on the floor with your side facing the pulley, grasping the cable attachment with your far arm and holding it across your waist. Pull the attachment away from the body externally, rotating the shoulder. The internal rotation is performed the same way, only you grasp the low pulley with the arm closest to the cable and internally rotate the shoulder, bringing the pulley toward you until your forearm is across your belly. The teres minor and posterior deltoids are synergists, or helper muscles, for this exercise.
Seated rows involve backward movement toward the midline of the body, moving the shoulder blades back toward the spine as the shoulder girdle is retracted or pulled back. Seated rows work multiple muscles, including the posterior deltoids, teres minor and infraspinatus muscles. Seated on a bench or platform, closely grasp the cable attachment and pull it toward your waist. A common error made when performing this exercise is rounding the back or bending at the waist and reaching forward toward the cable machine. Your back should be erect and not move during this exercise. Concentrate on squeezing or pinching your shoulder blades backward and together as you pull the cable toward your waist.
Rear Deltoid Fly
The rear deltoid fly can be performed using a resistance band, deltoid fly machine or dumbbells. Sit on a stability ball as you perform this this exercise, as you must engage your core or abdominal muscles to keep your balance. Rear deltoid flies target the posterior deltoid, trapezius and infraspinatus muscles. Seated on a stability ball with your feet together, hold a dumbbell in each hand and bend forward at the waist, head in line and eyes focused downward. Pinch your shoulder blades together and use your upper back muscles to lift the dumbbells out to the side, at about shoulder-height. Pause and lower. Be sure to keep your shoulders pressed down, away from your ears, during this exercise.
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