Variability in baseball pitching biomechanics among various levels of competition.

The aim of this study was to compare within-individual variability in baseball pitching among various levels of competition. It was hypothesized that variability decreases as level of competition increases. Five fastballs were analysed for 93 healthy male baseball pitchers (20 youth, 19 high school, 20 college, 20 Minor League, and 14 Major League level pitchers). Eleven kinematic, four temporal, and six kinetic parameters were quantified with a 240-Hz automated digitizing system. Three multiple analyses of variance were used to compare individual standard deviations for kinematic, temporal, and kinetic parameters among the five competition levels. There was a significant overall difference in kinematics and in six of the eleven kinematic parameters analysed: foot placement, knee flexion, pelvis angular velocity, elbow flexion, shoulder external rotation, and trunk forward tilt. Individual standard deviations tended to be greatest for youth pitchers, and decreased for higher levels of competition. Thus pitchers who advanced to higher levels exhibited less variability in their motions. Differences in temporal variation were non-significant; thus variability in pitching coordination was not improved at higher levels. Differences in kinetic variation were non-significant, implying no particular skill level has increased risk of injury due to variation in joint kinetics.