Relationship Between Physiological Variables and Linear Bat Swing Velocity of High School Baseball Players

PURPOSE: To determine the relationship of physiological variables to linear bat swing velocity before and after completing a 12-week resistance training program. METHODS: Forty-nine high school baseball players (age = 15.4 ± 1.2 yr) were randomly assigned to 1 of 2 training groups. Group 1 (n = 24) and group 2 (n = 25) both performed a stepwise periodized resistance exercise program and took 100 swings a day, 3 days a week for 12 weeks with their normal game bat. Group 2 performed additional rotational and full-body medicine ball exercises 3 days a week for 12 weeks. Ten physiological and sport-specific skill variables were measured pre-and posttraining. Parallel squat (PS) and bench press (BP) were measured by a 3 repetition maximum (RM) strength test. Estimation of 1RM for both tests was then calculated. Dominant (DTRS) and non-dominant torso rotational strength (NDTRS) were measured by a torso rotation machine. Sequential hip-torso-arm rotational strength was measured by a medicine ball hitter's throw. A 3-site skinfold test was used to determine percent body fat (%BF) and lean body mass (LBM). Angular hip velocity (AHV), angular shoulder velocity (ASV), and linear bat swing velocity (BV) were measured by a motion capture system which identified and digitally processed reflective markers attached to participant's bat and body. RESULTS: Correlation coefficients were calculated for all variables by utilizing a correlation matrix from raw scores for both the pre and posttraining data. Statistical analysis indicated a significantly high positive relationship (p < 0.05) between BV and post-NDTRS (r = 0.83). Significant moderately high positive relationships were indicated between BV and pre-NDTRS (r = 0.62) and post-DTRS (r = 0.74). Significantly moderate positive relationships were indicated between BV and pre- LBM, PS, BP, and ASV (r = 0.58, 0.48, 0.49, and 0.53); BV and post-LBM, medicine ball hitter's throw, PS, and BP (r= 0.59, 0.57, 0.55, & 0.48). CONCLUSION: These data suggest that significant relationships do exist between physiological variables and BV, but one cannot interpret this to mean a causal relationship. It also suggests that strength training programs designed to improve BV should emphasize improving rotational strength, LBM, lower and upper body strength, and explosive rotational power.