Szymanski, D. J., McIntyre, J. S., Szymanski, J. M., Bradford, T. J., Schade, R. L., Madsen, N. H., & Pascoe, D. D. (2007). Effect of torso rotational strength on angular hip, angular shoulder, and linear bat velocities of high school baseball players. Journal of Strength and Conditioning Research, 21, 1117-1125.

This investigation examined the effect of torso rotational strength on angular hip, angular shoulder, linear bat-end, and hand velocities, and three repetition maximum torso rotational and sequential hip-torso-arm rotational strength (medicine ball hitter's throw) in high school baseball players (N = 49). Ss were randomly assigned to either of two 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, three days a week, for 12 weeks with their normal game bat. Group 2 performed additional rotational and full-body medicine ball exercises three days a week for 12 weeks. A 3 RM parallel squat and bench press were measured at 0 and after 4, 8, and 12 weeks. Ss were pre- and post-tested for 3 RM dominant and non-dominant torso rotational strength and medicine ball hitter's throw. Angular hip velocity, angular shoulder velocity, linear bat-end velocity, and hand velocity were recorded pre- and post-training by a motion capture system that identified and digitally processed reflective markers attached to each S's bat and body.

Both groups increased linear bat-end velocity, hand velocity, 3 RM dominant and non-dominant torso rotational strength, and medicine ball hitter's throw after 12 weeks. Group 2 increased angular hip velocity and angular shoulder velocity. Group 2 showed greater improvements in bat-end velocity, angular hip velocity, angular shoulder velocity, 3 RM dominant and non-dominant torso rotational strength, and medicine ball hitter's throw than did Group 1. Groups 1 and 2 increased similarly in 1 RM parallel squat and bench press strength after 12 weeks [since both groups did the same amount of training on these exercises].

Implication. Performing additional rotational medicine ball exercises two days a week for 12 weeks significantly improves variables associated with the exercise. [There is no evidence in this study that suggests extra improvements in the study-variables resulted in better hitting performance, although that suggestion permeates the discussion and expression within the article.]

This study essentially showed that greater volumes of training on certain exercises produce more improvements in the variables associated with those exercises.

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