Less Deviation of Shoulder Elevation Is Associated with Ball Velocity in National Collegiate Athletic Association...

Efficient baseball pitching relies on coordinated trunk-arm coupling during the acceleration phase. Shoulder elevation is commonly maintained near 90°, and prior work has focused on discrete metrics rather than continuous regulation. Our purpose was to examine whether the deviation of shoulder elevation from 90° during the acceleration period was associated with ball velocity. Markerless kinematic data were collected from 362 National Collegiate Athletic Association pitchers (7,239 pitches). Shoulder elevation was defined as the relative angle between the trunk and the upper arm, and root mean square deviation from the 90° reference was calculated across the acceleration period. Two-level linear mixed-effects models were used to evaluate within- and between-pitcher associations. Shoulder elevation deviation demonstrated high between-pitcher consistency (intraclass correlation coefficient=0.95). Reduced root mean square deviation was associated with higher ball velocity at both the between-pitchers (β=- 0.06 mph·deg^-1, p = 0.006) and within-pitchers (β=- 0.07 mph·deg^-1, p = 0.004) levels. Allowing pitcher-specific slopes significantly improved a model fit, indicating heterogeneity in the magnitude of this association and suggesting that the reduced deviation of shoulder elevation during acceleration is associated with higher ball velocity. Continuous quantification of shoulder elevation during the acceleration phase provides a complementary perspective to discrete joint angle analyses and may serve as an indicator of pitching performance.