Investigating Drill Constraint Kinematics in Male Baseball Pitchers

Abstract

Pitching requires the development of high forces (Werner et al., 1993; Fleisig et al., 1995) to be generated in short periods of time (Werner et al., 1993; Seroyer et al., 2010). The ecological dynamics approach can be used to enhance these qualities through the use of constraint drills (Wilk et al., 2002; Wilk et al., 2009; Brady et al., 2020; Gray, 2020). In this framework, coaches aim to implement a variety of appropriate constraints to help facilitate an effective search for successful movement solutions (Renshaw et al., 2010). This study aimed to use pitchAITM (Dobos et al., 2022) to 1) determine kinematic differences that pitching constraint drills (e.g. medicine ball shot put drill, pivot pickoff drill, foot-up rocker drill, walk-in drill, towel drill, janitor drill, drop step drill, and long toss) elicit compared to a typical baseball pitch, and 2) determine the effect of experience, fatigue, intensity, height and weight on kinematics. 25 male baseball pitchers with average height (183.16 ± 6.28 cm), weight (87.48 ± 9.38 kg), and pitch velocity (34.57 ± 2.89 m/s) were included in this study. pitchAITM videos of pitches and drills were captured, and demographic information, prior drill experience, pre and post-testing fatigue collected at two different baseball training facilities. Extracted pitchAITM data included five joint angles, four maximum joint angles, five maximum rotational velocities, and nine timing related metrics. Multiple linear fixed effects models revealed a total of 127 unique significant kinematic differences in response variables across all measured pitching constraint drills compared to the pitching delivery. Prior drill experience, fatigue, intensity, height and weight also had significant influence on measured kinematics. This work demonstrates the first collective approach to studying the biomechanics of common constraint drills, in which coaches can refer to when choosing appropriate drills for effective practice design.