The subscapularis is one of the four rotator-cuff muscles that act on your shoulder, facilitating inward rotation of the humerus bone within the shoulder socket. The muscle crosses in front of your shoulder joint, attaching to the scapula bone in your upper back on the inside and to the front of the humerus on the outside. Strengthening the subscapularis involves performing resistance exercises that activate the muscle on a regular basis as part of a well-designed program.
Performing isometric exercises that target the subscapularis involves contracting the muscle for five to 10 seconds at a time without moving your shoulder joint considerably. A physical therapist may recommend these exercises as part of a rehabilitation program for an injured rotator cuff.
Start on your back with your elbow about 6 inches away from your side and flexed to 90 degrees, so your forearm points upward. Place a large book by your hip on the same side. Inwardly rotate your shoulder, placing your hand on top of the book, and press downward for five to 10 seconds. Relax briefly, then move your elbow about 3 inches farther away from your side and repeat the same exercise. Perform the exercise twice more -- once with your upper arm pointed away from your shoulder and once with your elbow even with your ear. Repeat the series with your opposite arm.
Side-Lying Internal Rotation
Perform the side-lying internal rotation exercise with a dumbbell while lying on a flat bench or table. Start with the dumbbell in your left hand and lie on your left side with your elbow tucked into the left side of your abdomen and your forearm pointed forward, extended over the edge of the bench. Lift the weight until your forearm touches your belly, then lower it slowly and repeat. Complete at least eight repetitions, then turn over and switch arms.
You may perform several resistance-band exercises to strengthen the subscapularis muscle. The first is similar to the side-lying internal rotation exercise, but you execute the exercise from a standing position. You hold one end of the resistance band in your hand with the other end attached to a sturdy object at belly-button height.
A second example is the diagonal exercise, which is highlighted in a 2003 study published in "The American Journal of Sports Medicine." Stand with your left foot behind your right and the free end of the band in your left hand, with your arm pointing sideways and away from your shoulder. Your elbow should be flexed slightly and your palm should be facing forward. Inwardly rotate your upper arm and move your hand diagonally downward to stretch the band until your hand is in front of your right hip. Reverse to the starting position slowly and repeat. Do the exercise with your right arm as well.
The same investigation from "The American Journal of Sports Medicine" found that the pushup plus is another effective exercise for the subscapularis. Perform the exercise just like a traditional pushup, but press your shoulders forward to protract the scapula bones at the top of the upward-movement phase and begin the downward-movement phase by moving your shoulders backward to retract the scapula bones. Complete multiple repetitions per set.