The relationship between variability in baseball pitching kinematics and consistency in pitch location.

The purpose of this study was to explore the relationship between variability in pitching kinematics and consistency in pitch location. Data were collected for 47 healthy baseball pitchers throwing ten full-effort fastballs to the centre of the strike zone. For each pitch, 20 kinematic parameters were calculated with an automated motion capture system while pitch location was measured with a PITCHf/x system. Variability of each kinematic parameter was defined for each pitcher as the standard deviation among his fastballs thrown. For calculating consistency, each pitcher's mean pitch location was first calculated. The distances from each individual pitch to the mean pitch location were then found for each pitcher tested. A consistency metric was then calculated for each pitcher by averaging these distances. A multiple linear regression model was developed using stepwise regression with backwards elimination. The resulting model explained 58% of the variance in the consistency metric and included five parameters, three at foot contact (upper trunk tilt, shoulder abduction, and shoulder horizontal abduction) and two at time of maximum shoulder external rotation (shoulder external rotation and shoulder horizontal adduction). Reducing variability at the shoulder during the early portions of the pitching motion may improve consistency of ball location.

The influence of mound height on baseball movement and pitching biomechanics.

OBJECTIVES: To determine whether mound height is associated with baseball movement (velocity, spin and break) and baseball pitching biomechanics (kinematics and kinetics). DESIGN: Controlled laboratory study. METHODS: Twenty collegiate baseball pitchers threw five fastballs and five curveballs from four different mound heights (15cm, 20cm, 25cm, 30cm) in a randomized order. Ball movement was computed by a ball tracking system, while pitching biomechanics were calculated with an 11-camera optical motion capture system. Repeated measures analysis of variance was utilized to detect significant differences among the four different mound heights (p<0.05) for the fastball and curveball pitches. RESULTS: There were no significant differences observed for ball movement. There were seven significant kinematic differences for fastballs and eight kinematic differences for curveballs. Although these differences were statistically significant, the magnitudes were small, with most joint angles changing by less than 2°. There were no significant kinetic differences for curveballs, but five kinetic parameters (elbow varus torque, elbow flexion torque, elbow proximal force, shoulder internal rotation torque, and shoulder anterior force) varied with mound height for fastballs. In general, fastball kinetics were 1%-2% less from the lowered (15cm, 20cm) mounds than from the standard (25cm) or raised (30cm) mounds. CONCLUSIONS: Lowering the mound may not affect a pitcher's ball movement, but may slightly reduce shoulder and elbow kinetics, possibly reducing the risk of injury.