In 2012, a groundbreaking study, Maenhout, et. al., have uncovered crucial insights into the shoulder mechanics of athletes who regularly engage in overhead sports, such as baseball, tennis, and swimming. The study, led by Annelies Maenhout and her team, investigated the link between glenohumeral internal rotation deficit (GIRD) and shoulder impingement, offering a promising intervention for affected athletes.

Athletes performing repetitive overhead motions often experience a loss of internal rotation range of motion (ROM) on their dominant side. This condition, known as GIRD, has been associated with altered shoulder and scapular movements, potentially leading to a decrease in the subacromial space, thereby contributing to subacromial impingement—a painful condition that can hinder athletic performance and daily activities.

The primary aim of the study was twofold: to quantify the acromiohumeral distance (AHD)—a critical measure of subacromial space—and compare it between the dominant and nondominant shoulders of overhead athletes with significant GIRD. Secondly, the study evaluated the effectiveness of a specialized stretching program in improving ROM and AHD.

Sixty-two overhead athletes with GIRD greater than 15 degrees participated in the study. Using a digital inclinometer, the researchers measured ROM, while ultrasound technology provided precise AHD measurements. The athletes were then randomly assigned to either a control group or a stretch group, with the latter engaging in a six-week sleeper stretch program targeting the dominant shoulder.

Initial measurements confirmed that athletes with GIRD had a notable internal rotation deficit (-24.7° ± 6.3°) and horizontal adduction deficit (-11.8° ± 7.4°) on their dominant side. Correspondingly, the AHD was significantly smaller on the dominant side, indicating a reduced subacromial space.

Post-intervention results were promising. The stretch group exhibited significant improvements: internal rotation increased by +13.5° ± 0.8°, horizontal adduction improved by +10.6° ± 0.9°, and AHD expanded by +0.5 to +0.6mm. No significant changes were observed in the control group or the nondominant shoulders of the stretch group, underscoring the targeted effectiveness of the sleeper stretch program.

The study’s findings highlight the potential of specific stretching programs to mitigate the effects of GIRD and possibly prevent subacromial impingement in overhead athletes. This research paves the way for further investigations to solidify the clinical applications of these results, aiming to enhance athletic performance and reduce injury risks.

As the understanding of shoulder mechanics continues to evolve, this study marks a significant step toward more effective treatment strategies for athletes, ensuring they remain at the top of their game while safeguarding their long-term health.

Reference: Maenhout, A., Van Eessel, V., Van Dyck, L., Vanraes, A., & Cools, A. (2012). Quantifying acromiohumeral distance in overhead athletes with glenohumeral internal rotation loss and the influence of a stretching program. The American journal of sports medicine, 40(9), 2105-2112.