The Relationship Between Relative Humeral Retrotorsion Difference and Shoulder Strength Measures in Collegiate Baseball Athletes.

Background: Humeral retrotorsion (HRT) has been linked to several throwing-related adaptations in baseball athletes, including glenohumeral range of motion, posterior capsule extensibility, throwing velocity, and injury risk. Studies have shown that rotational strength deficits can be linked to risk of injury, yet no studies have addressed the effect of side-to-side differences in HRT (relative HRT [rHRT]) and its relationship to rotational strength profiles. Purpose/Hypothesis: The purpose of this study was to determine the relationship between rHRT and shoulder strength measures. It was hypothesized that there would be a significant association between shoulder external rotation (ER) and internal rotation (IR) strength and rHRT in a cohort of uninjured collegiate baseball athletes. Study Design: Cross-sectional study; Level of evidence, 3. Methods: A total of 182 uninjured male collegiate baseball athletes participated in this study. Bilateral isometric rotational shoulder strength was measured for each participant utilizing a handheld dynamometer, while diagnostic ultrasound was used to measure humeral torsion. Multiple hierarchal regression was conducted to determine whether rHRT significantly contributed to measures of shoulder strength; additionally, subanalyses were conducted to determine if playing position or limb dominance significantly contributed to model fit. Results: Relative HRT did not significantly contribute to prediction models for dominant limb ER, nondominant limb ER, and nondominant limb IR strength ( Conclusion: Relative HRT is associated with dominant limb IR strength. Additionally, effects of playing position (pitcher) and limb dominance (left-handed) independently and positively contributed to these strength prediction models, demonstrating an association between shoulder IR strength and rHRT, playing position, and limb dominance.