Effects of strength training on throwing velocity and shoulder muscle performance in teenage baseball players

Exercise protocols designed to improve muscle function and athletic performance are continually developed and revised, often without published research supporting their efficacy. This study compared the effects of isokinetic (IKN) and accommodative isotonic training in the individualized, dynamic, variable resistance (IDVR) mode. Twenty-seven teenage baseball players were tested isokinetically for dominant shoulder rotational peak torque and power and for throwing velocity. They were then randomly assigned to 5 weeks of IKN training, IDVR training, or a control group of no training. Following the training period, pretest protocols were repeated. Analysis of variance of differences in means and Newman-Keuls post hoc tests showed statistically significant increases in throwing velocity and external rotator torque in the IDVR group but not the IKN group. External rotator power improved in both groups. Internal rotator torque and power were not improved in either group. Results suggest that IDVR may be more effective than IKN training in improving throwing velocity and external rotator torque production. Clinicians should consider using IDVR protocols in improving shoulder muscle function and throwing performance. J Orthop Sports Phys Ther 1992;15(5):223-228.