Influence of Humeral Retrotorsion on Glenohumeral Range of Motion in Healthy Collegiate Softball Players

Background Anatomic humeral retrotorsion (aHRT) influences objective measures of glenohumeral external (GER) and internal rotation (GIR) range of motion (ROM) in baseball players. Baseball players often display GER deficits within the context of aHRT; however, this has yet to be studied in a softball population. Hypothesis/Purpose: 1) To determine if there are differences in GER ROM, GIR ROM, total range of motion (TROM), aHRT, relative humeral retrotorsion (rHRT), and HRT-corrected motion between collegiate softball position players and pitchers, 2) to determine if differences exist between GER and HRT-corrected GER and GIR and HRT-corrected GIR in collegiate softball players, regardless of position. Study Design Retrospective Descriptive Study Methods Sixty-three healthy Division I softball players participated. Objective measures of GER, GIR, and aHRT on the throwing arm and non-throwing were collected using a digital inclinometer at various timepoints during the 2023-2024 seasons. TROM, rHRT, and HRT-corrected motions were calculated from objective measurements on the throwing arm and non-throwing arm. Independent t -tests were used to determine differences in objective ROM and HRT measures between position. Paired t-tests were used to determine differences between objective ROM and HRT-corrected ROM in both the pitching and position player cohorts. Effect sizes were calculated. Results There were no significant differences in GER, GIR, TROM, aHRT, rHRT, HRT-corrected GER, and HRT-corrected GIR by player position (p> 0.05). Effect sizes ranged from -0.27-0.57. There were differences in position players between GER (5 ± 8°) and HRT-corrected GER (-11 ± 14°) (p < 0.001) and GIR (-10 ± 10°) and HRT-corrected GIR (6 ± 12°) (p < 0.001). There were differences in pitchers between GER (1 ± 8°) and HRT-corrected GER (-11 ± 11°) (p < 0.001) and GIR (-7 ± 9°) and HRT-corrected GIR (5 ± 10°) (p < 0.001). Conclusion When glenohumeral ROM is interpreted within the context of rHRT, GIR deficits are not common in softball players. Based on the current findings, it is imperative that rHRT be assessed in all softball players as this information will aid in the identification of true motion restrictions.