Joint and Segment Sequencing and Its Relationship to Ball Velocity and Throwing Arm Kinetics In Professional Pitchers.

Overview

abstract

BACKGROUND: Temporal variations during the pitch have demonstrated significant impacts on the kinetic chain, and as such, have implications in injury risk. PURPOSE: To determine the effect of varying chronological orders of maximum joint and segment velocities on ball velocity and upper extremity kinetics. METHODS: Professional baseball pitchers (n=287) were assessed with 3D-motion capture (480 Hz) while pitching. Pitches were categorized into one of the following groups dependent on the first maximum joint or segment velocity achieved out of chronological order in an inferior to super direction: knee extension (DscK), pelvis rotation (DscP), trunk rotation (DscT), shoulder rotation (DscS), forearm pronation (DscF), and Proper (for pitchers with the correct temporal sequence), and Total Population, for all pitchers. Ten normalized throwing arm kinetic variables were compared among groups. Regression analysis was conducted on the timing of maximum velocities with ball velocity. RESULTS: The majority of pitches were in the DscK group (64.5%). The DscK group had significantly slower maximum lead knee extension velocity compared to the Proper group (253 vs 316 º/s, p=0.017). The Proper group had significantly faster ball velocity compared to the Total Population (39.0±1.9 vs 38.3±2.1 m/s, p = 0.013). The DscP group had significantly slower maximum pelvis rotation velocity compared to the Proper group (596 vs 698 º/s, p<0.001). The Proper group had no significant difference in kinetics relative to the population. For every 1 standard deviation (SD) delay in attaining maximum lead knee extension velocity, ball velocity increased by 0.38 m/s (B=3.5, β=0.18, p<0.001). For every 1 SD delay in timing to achieve maximum pelvis rotation velocity, maximum pelvis rotation velocity and ball velocity increased by 22.5 º/s (B=1107.0, β=0.23, p<0.001) and 0.48 m/s (B=23.4, β=0.23, p<0.001), respectfully. CONCLUSION: Pitchers with discordant sequence of knee extension and pelvis rotation velocity timing had significantly slower corresponding segment/joint velocities. Conversely, pitchers with proper sequence had the fastest ball velocity with minimal differences in throwing arm kinetics. To maximize ball velocity, professional pitchers should consider achieving maximal velocities in an inferior to superior chronological sequence, with a particular focus on the knee and pelvis.