The sleeper stretch is a common mobility exercise, frequently employed by athletes who engage in repetitive overhead movements, such as baseball pitchers or swimmers. This passive stretch is performed lying on the side and is designed to improve the rotational movement of the shoulder joint. Its primary function is to increase the range of motion available for internal rotation, a movement often restricted in athletic and non-athletic populations. Understanding the structures this exercise targets is necessary for effective and safe performance.
The Primary Target: Posterior Shoulder Capsule
The sleeper stretch primarily aims to elongate the posterior shoulder capsule, a deep, non-contractile structure of the joint. The capsule is a network of ligamentous tissue that surrounds the glenohumeral joint, providing static stability to the shoulder. Tightening of the posterior capsule is a common issue, particularly in the dominant arm of throwing athletes.
When this tissue becomes stiff or shortened, it restricts the inward rotation of the arm. A tight posterior capsule can mechanically shift the humeral head forward and slightly upward within the socket during overhead movements. This altered positioning can lead to friction and irritation of the soft tissues at the front of the shoulder, contributing to shoulder pain and impingement symptoms. Successfully stretching this tissue requires a low-load, long-duration force to encourage plastic changes in the ligament structure.
Secondary Muscles Targeted
While the posterior capsule is the main focus, the sleeper stretch also elongates the muscles that cover the back of the shoulder joint. These include key components of the rotator cuff that perform external rotation, specifically the infraspinatus and the teres minor, which are stretched as the arm is pushed into internal rotation.
The posterior portion of the deltoid muscle is also placed on stretch during the movement. Although these muscles are receiving elongation, the stretch is not intended to be a primary muscle-stretching exercise. The positioning, with the scapula stabilized against the ground, helps direct the force deeply into the joint capsule, making it distinct from other muscular stretches like the cross-body arm pull.
Proper Technique for Safe Execution
To begin the sleeper stretch, lie on the side of the shoulder you intend to stretch, supporting your head with a pillow. Position the stretching arm so the shoulder is abducted to approximately 90 degrees, extending straight out from the body. Bend the elbow to 90 degrees with the forearm pointing toward the ceiling. Ensure the shoulder blade (scapula) remains stabilized against the floor to isolate the stretch to the glenohumeral joint.
Use the opposite hand to gently push the forearm down toward the floor, passively rotating the shoulder inward. Apply the force slowly and gradually, aiming for a mild to moderate stretching sensation in the back of the shoulder. Pinching or pain in the front of the shoulder indicates improper technique and potential impingement, requiring an immediate reduction in force or adjustment of the arm position. Holding the stretch for 30 seconds for multiple repetitions is a common recommendation to affect the capsular tissue.
Clinical Purpose: Addressing Internal Rotation Deficit
The sleeper stretch is a common intervention for a condition frequently seen in overhead athletes called Glenohumeral Internal Rotation Deficit, or GIRD. GIRD is defined as a loss of internal rotation range of motion in the dominant arm compared to the non-dominant arm. This deficit arises when the posterior shoulder structures, particularly the capsule, tighten due to the repetitive, high-velocity external rotation movements of throwing.
The primary biomechanical concern with GIRD is the increased risk of injury caused by altered shoulder mechanics during the late cocking and early acceleration phases of an overhead activity. The tight posterior capsule shifts the humeral head, increasing stress on the anterior joint structures and potentially leading to labral tears or internal impingement. Corrective exercises like the sleeper stretch seek to restore the lost internal rotation to re-center the humeral head within the joint socket. By improving the flexibility of the posterior capsule, the stretch helps normalize the rotational range of motion, reducing the strain on other joint structures and mitigating the risk of future injury.