Poster 161: Musculoskeletal Adaptations to Baseball Pitching Differ Markedly Between Righthand Dominant Versus Lefthand Dominant Pitchers

Objectives: Musculoskeletal adaptations on the dominant arm of baseball pitchers are typically (1) a gain in glenohumeral external rotation (ER) range motion (ROM), (2) loss internal (IR) ROM, (3) posterior shoulder tightness, (4) weakness empty can test, and (5) increased IR strength. The purpose this study was to determine if these differed between righthand (RHD) versus lefthand (LHD) pitchers. Based recent work it hypothesized that ROM would be less apparent LHD pitchers, but strength not differ RHD Methods: Shoulder were measured 327 preseason screening (91 tested more than one season, 418 player-seasons, 322 vs. 96 LHD). There 157 youth (age 11-15 yr) 146 adolescent 16-17 115 adult 18-24 yr). ER (Tyler test) with digital level. Empty can, ER, scapular retraction hand-held dynamometer. Differences nondominant arms, age groups, assessed using mixed model analysis variance (mean SD reported). Results: Adaptations had 11±10° (P<0.001) no difference (0±10°, P=0.685). unaffected by (P=0.829). for (10±11°) greater (5±10°). This (RHD 9±9° 1±9°, P<0.001) 12±10 5±11°, 9±14° 8±10°, P=0.863; Age Group P=0.040). Total (ER+IR ROM) also effect (Age P=0.027): 4±15° total side (P=0.007) while 7±10° (P=0.002). Posterior tightness affected dominance (P=0.038); there (youth 6±13° 10±11°, P=0.156; 5±10° 8±15°) (6±8° 1±11°, P=0.032). Strength For weaker (5±15%, arms (3±16% stronger P=0.100; P<0.001). strength, (7±17%, (2±21% P=0.360; By contrast, (6±19%, P=0.007) (0±15% P=0.723; P=0.003). Dominant different (P=0.323). Conclusions: typical seen mostly absent, or diminished, some dependent effects ROM. Adult paradoxically without associated shoulder. opposite case having absence loss. have been reported previously. Epidemiological studies examining role injury risk previously accounted differences lefthanded righthanded