A Comparative Study on the Kinetic and Kinematic Characteristics of the Shoulder Complex According to the GIRD in Amateur Baseball Players

PURPOSE: This study aimed to determine the differences in kinetic and kinematic variables of the shoulder complex in amateur baseball players based on the presence of a glenohumeral internal rotation deficit (GIRD).METHODS: Thirty-one participants were recruited for the study, including those with no history of neck or upper extremity injuries within the past six months. The range of motion (ROM) of the glenohumeral joint was evaluated, along with the isokinetic concentric and eccentric torques of the internal and external rotators. In addition, scapular alignment, isometric strength of the scapular muscles, and the Korean Kerlan–Jobe Orthopedic Clinic (K-KJOC) Shoulder and Elbow scores were assessed.RESULTS: Internal rotation ROM (<i>p</i>=.014), middle trapezius strength (<i>p</i>=.027), and K-KJOC scores (<i>p</i>=.022) were significantly lower in the GIRD group than in the non-GIRD group. Conversely, the scapular depression angle was significantly higher in the GIRD group (<i>p</i>=.008). Moreover, a fair positive correlation was observed between GIRD and scapular depression angle (r=.440), as well as between internal rotation ROM and K-KJOC score (r=.467).CONCLUSIONS: Our results emphasize the need for the regular assessment of key parameters, namely middle trapezius strength, scapular depression, and shoulder and elbow function, in amateur baseball players with GIRD. Moreover, implementing personalized intervention strategies to restore these variables may be crucial in reducing the risk of injury.