The rotator cuff refers to a group of four distinct muscles and tendons that connect to each shoulder and stabilize the humerus, the upper arm bone. These muscles are engaged when you move your shoulder, and work together to give you the needed range of motion to toss a ball or reach for an object on a high shelf.
Baseball pitchers and other athletes aren't the only people who experience rotator cuff injuries. The American Academy of Orthopaedic Surgeons estimates that nearly 2 million Americans see a doctor about a rotator cuff problem every year. Strengthening this group of muscles can help enhance the stability of this important joint and help you avoid injury.
Alternating arm and leg lifts: Position yourself on all fours. Your arms are straight, with hands directly below your shoulders and your knees directly below your hips. Tighten your core muscles and simultaneously extend your left leg and your right arm straight out so that they're both parallel to the floor. With control, lower them, and repeat 10 to 15 times. Then repeat the sequence with your right leg and left arm.
Stability ball pushups: Take pushups to another level by doing them with your hands on a stability ball. From the same position on all fours, place your hands on the ball, shoulder width apart, with your upper arms pressed against your sides. Straighten your legs, with toes flat on floor. Keeping your body in a straight line from head to feet, straighten your arms, pushing your body away from the ball. Hold briefly, then bend elbows to return to the start position. Repeat 10 to 15 times.
The American Council on Exercise has more on rotator cuff muscles and how to strengthen them safely.