The infraspinatus and supraspinatus are two of the four rotator cuff muscles that act on the humerus bone of your upper arm within your shoulder socket. Exercising these muscles regularly helps increase your shoulder joint's range of motion and muscular strength, and may prevent certain shoulder injuries that are common among athletes who execute overhead striking and throwing movements frequently. Consult a professional to determine which exercises are appropriate for you.
Anatomy and Biomechanics
The infraspinatus attaches to the infraspinous fossa on the back, inside portion of the scapula bone within your upper back on the inside and to the back of the humerus bone, near the shoulder joint, on the outside. The supraspinatus, on the other hand, attaches to the supraspinous fossa on the scapula bone on the inside and near the same location on the humerus bone as the infraspinatus on the outside. Both muscles assist with lateral, or outward, rotation of the humerus bone within the shoulder socket. Additionally, the infraspinatus helps with horizontal abduction and the supraspinatus with abduction.
Infraspinatus/Supraspinatus Exercises
Stretching the infraspinatus and supraspinatus muscles by medially, or inwardly, rotating your upper arms as far as is comfortable can help increase your shoulder joint's range of motion. Do this by placing the backs of your hands on your hips and pressing your elbows together in front of your abdomen until you feel a gentle stretch. Hold this position for 10 to 30 seconds.
Strengthening the muscles requires rotating your upper arms repeatedly in both directions against external resistance. For example, lie on your side on a bench, hold a dumbbell in your top hand, and repeatedly lift and lower the weight with your elbow anchored to your ribs and your forearm across your abdomen. Another variation involves executing the same movement from a standing position with a resistance band instead of a dumbbell.
Infraspinatus Exercises
Along with lateral rotation, the infraspinatus assists the middle and posterior portions of the deltoid muscle and the teres minor muscle with horizontal abduction, which occurs when you arc your arms away from each other from in front of your chest. You can stretch the infraspinatus, therefore, by pulling your arm across your chest with your opposite arm for at least 10 seconds, and strengthen the muscle by performing the reverse fly, which involves horizontally abducting your arms repeatedly while bending forward from a standing position or lying face-down on a bench.
Supraspinatus Exercises
The supraspinatus helps the middle portion of the deltoid with shoulder joint abduction, which occurs when you lift your arms sideways, away from your body. Stretch the muscle just like the horizontal abductors, but pull your arm across your neck so it's angled upward from your shoulder instead of across your chest, and perform lateral raises, which involves abducting your arms to shoulder height from your hips, to strengthen the supraspinatus in this fashion.
References
- "Basic Biomechanics"; Susan J. Hall; 2007
- "NSCA's Essentials of Personal Training"; Roger Earle and Thomas Baechle; 2004
- ExRx.net: Infraspinatus and Teres Minor
- ExRx.net: Shoulder Exercise Menu
