Shoulder External Rotation (With Cable) Strengthening the muscles that support your shoulder will help keep your shoulder joint stable. Stand, hold the cable (or resistance band), bend the elbow upward to 90 degrees, and hold your upper arm at the side of the body. Place the body such that the cable pulls sideways toward the inactive arm. The target muscles are the shoulder external rotators. What muscles does external rotation work? In red we can see how the infraspinatus muscle externally rota