(57) CONTRIBUTIONS OF BAT SWING METRICS TO EXIT VELOCITY IN COLLEGIATE BASEBALL PLAYERS

Purpose: The purpose of this study was to examine what contributions of bat swing metrics influence exit velocity in collegiate baseball players. Methods: Collegiate baseball players (n=11; Mean±SD; age=20.4±1.4 yrs, height=1.82±0.08 m, bodyweight=86.8±7.7 kg) performed testing procedures including 10 swings for maximum batted ball velocity off a tee. Each swing condition was performed with a Blast accelerometer (Blast Motion, San Marcos, CA) attached to the end of their own baseball bats. A zero-order correlation matrix was run between all of the independent variables (accelerometer metrics), in order to remove variables with high shared variance. Following the zero order correlation, a forward-entry-model multiple regression analysis was used to determine significant contributing metrics to batted ball velocity (p< 0.05). A Jackknife statistical analysis was performed to estimate bias. Results: Seven variables significantly contributed to the regression, Bat Power (kW) (r=0.396), On-Plane Efficiency (%) (r= 0.467), Connection Score (r=0.509), Peak Hand Speed (mph) (r=0.528), Early Connection (degrees) (r=0.547), Vertical Bat Angle (degrees) (r=0.557), Time-to-Contact (seconds) (r=0.562). The adjusted R-square indicated that 56.2% of the variance in batted ball velocity was accounted for by the multiple regression. The standard error of the resulting prediction equation for exit velocity was 4.38 mph. All variables entered into the multiple regression exhibited no bias and had homogeneity of variance for all independent variables. Conclusions: The findings of the present study found 7 out of 12 metrics contributed significantly to the 56.2% variance accounted for by bat swing metrics alone. The other 43.8% of unexplained variance or variance unaccounted for may come from other factors such as ground reaction forces, body kinematics, and more. Practical Applications: By understanding the contributions that influence ball exit velocity, coaches can understand what areas of focus that some athletes may need in order to achieve max exit velocity. As pitch type and pitch location will likely affect swing mechanics and the decision-making process, further research is warranted to investigate how these factors play a role in may affect swing-related metrics, especially when facing a live pitcher. Acknowledgements: This project was supported by the Clara Wu and Joseph Tsai Foundation.