Pitching Kinematics But Not Countermovement Jump Kinetics Increase With Fall Practice Phases In Collegiate Baseball

Assessment of sports performance is commonly relegated to off field evaluations due to the impractical nature of biomechanical analysis. With advances in markerless motion capture, previously immeasurable hypotheses can now be examined, such as whether variations in practice phase impact off-field testing or pitching mechanics. PURPOSE: This study assessed lower extremity (LE) and center of mass (COM) pitching kinematics and countermovement jump (CMJ) kinetics during the Fall baseball season. We hypothesized that practice phase would affect LE and COM pitching kinematics and CMJ kinetics. METHODS: 18 collegiate pitchers (RH/LH: 15/3; Mass: 92.01 ± 1.90 kg; Height: 1.90 ± 0.06 m; Pitch Speed: 39.62 ± 1.42 m/s), participated in the Fall season, divided into bullpen (BP), where only the pitcher and catcher occupied the field of play and simulated game (SG) phases with batters present. Kinematics were derived from tracked key points using an 8-camera markerless motion capture system (300 Hz), specialized for pitching analysis. In parallel, CMJ kinetics were collected during training sessions using a wireless dual force platform system (1000 Hz). Paired t-tests were used to compare practice phases to pitching kinematics, and CMJ kinetics. RESULTS: Max stride phase COM velocity (to home plate) (MD ± SE [CI95]: 8.73 ± 1.92 [4.58, 12.87] cm/s, p < .001, Cohen’s d: 1.216), post stride foot contact COM velocity (away from home plate) (MD ± SE [CI95]: 7.99 ± 2.60 [2.10, 13.88] cm/s, p < .001, Cohen’s d: 0.970), stride length (MD ± SE [CI95]: 0.98 ± 0.28 [0.39, 1.57] % height, p = .004, Cohen’s d: 0.760), max pelvis rotation velocity (MD ± SE [CI95]: 15.99 ± 15.75 [-34.15, 66.14] degrees/sec, p = .046, Cohen’s d: 0.508), and pitch speed (MD ± SE [CI95]: 0.91 ± 0.48 [2.09, 10.33] m/s, p < .001, Cohen’s d: 1.910) were greater during SG compared to BP. Average vertical concentric force (MD ± SE [CI95]: -25.96 ± 11.13 [-49.18, -2.73] N, p = .045, Cohen’s d: -0.509) decreased during SG compared to BP, without differences in eccentric rate of force development (p = .79), or vertical concentric impulse (p = .30). CONCLUSIONS: Progression in practice phases drives increases in pitching kinematics without differences in CMJ kinetics, highlighting the practice setting as a modifiable variable in player development and rehabilitation programs.