Normal shoulder and hip rotational range of motion in elementary school male baseball players

Background Shoulder and hip rotational range of motion (ROM) have been reported to be associated with throwing-related shoulder and elbow injuries in baseball players. However, there is a lack of studies reporting the normal shoulder and hip rotational ROM in elementary school baseball players. The purpose of this study was to report the normal shoulder and hip rotational ROM in elementary school male baseball players based on field position, grade of elementary school, and baseball experience. Methods A large database of annual medical check-ups conducted for elementary school baseball players between 2019 and 2023 were reviewed. Shoulder internal rotation (IR) angle, shoulder external rotation (ER) angle, total shoulder rotational ROM (shoulder ER + IR), hip IR angle, hip ER angle, and total hip rotational ROM (hip ER + IR) of the uninjured baseball players were evaluated. All ROM angles were measured using a standard goniometer. The shoulder and hip rotational ROM were compared by the bilateral sides (throwing vs. nonthrowing side), field position (pitchers vs. nonpitchers), grade of the elementary school (between third to sixth grades), and pitching or baseball experience. Results A total of 1210 healthy elementary male baseball players (pitchers/nonpitchers, 590/620) with a mean age of 10.0 ± 0.9 (range, 8-12) years were finally included in this study. There were significant differences in all shoulder rotational ROM between the throwing and nonthrowing sides in all baseball players (p < 0.001). There were significant differences in shoulder ER angle (107.1 ± 13.4° vs. 104.2 ± 14.4°, p < 0.001) and total shoulder rotational ROM (164.7 ± 21.5° vs. 161.7 ± 21.7°, p = 0.02) of the throwing side between the pitchers and nonpitchers. There were significant differences in shoulder IR angle (p = 0.04) and total shoulder rotational ROM (p = 0.04) of the throwing side by grade of elementary school in pitchers, although no significant differences were found in any shoulder ROM in nonpitchers. There were significant differences in bilateral hip IR angles according to elementary school grade, regardless of field position. Finally, no significant differences in shoulder or hip rotational ROM were detected according to pitching experience or baseball experience. Conclusion The present study reported normal shoulder and hip rotational ROM in elementary school male baseball players based on field position, elementary school grade, and pitching or baseball experience using a large sample size. The findings of this study will serve as a reference for evaluating shoulder and hip rotational ROM in elementary baseball players.