BACKGROUND: A pitcher’s ability to locate the ball is a critical component of their performance. Research has shown that projection angle has the greatest influence on a throw’s location at target, yet limited literature exists regarding the relationship between release angles and kinematics. This study aimed to investigate kinematic predictors of vertical (VRA) and horizontal (HRA) release angles during Division I collegiate baseball games. METHODS: Kinematic data for seventy-seven Division I collegiate pitchers (1.88 ± 0.06m; 91.6 ± 9.2kg) were recorded using an 8-camera markerless motion capture system (KinaTrax Inc., FL, USA; 300 Hz). Ball flight metrics were collected with a Trackman V3 Game Tracking stadium unit. Kinematic and ball metric data were averaged for each pitcher, and variables exhibiting a significant relationship with VRA or HRA were included in two forward stepwise regressions (p = .05). VRA included 20 independent variables, whereas HRA included 15. RESULTS: Seven variables accounted for 69.4% of the variance in VRA (R2 = .694; F7,69 = 22.362; p < .001). Trunk lateral flexion at foot contact (FC) (β = -0.031) and maximal external rotation (MER) (β = 0.037); shoulder abduction angle at MER (β = -0.020); displacement of the center of mass (COM) in the anterior-posterior direction at ball release (BR) (β = 2.137); elbow pronation at BR (β = -0.012); ball velocity (β = -0.223); and the timing of maximal knee extension velocity relative to BR (β = .005) were all significant predictors (all p < .05). For HRA, pelvis tilt (β = 0.078) and COM velocity in the medio-lateral direction at FC (β = 1.164), and shoulder abduction angle at MER (β = 0.045) were all significant predictors (all p < .05), accounting for 43.2% of the variance (R2 = .432; F3,69 = 18.531; p < .001). CONCLUSION: Multiple kinematic factors appear to be key determinants of ball release angles during baseball pitching. By understanding the biomechanics associated with these release conditions, it is possible to determine which variables might be manipulated to improve ball projection towards target. For example, trunk lateral flexion might be used to alter VRA, whilst increasing shoulder abduction at MER may be used for either VRA or HRA.

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