Long-term training effects of weighted ball throwing programs have been well documented. However, the mechanisms by which these effects are facilitated are poorly understood due to the difficulty of measuring biomechanics in the baseball throwing motion. The purpose of this study is to replicate previous methods investigating within-session effects of throwing overload and underload baseballs to provide mechanistic evidence for weighted baseball training methods. We hypothesized that varying the pitched ball weight between three, four, five, six, and seven ounces will affect pitched ball velocity, upper body kinematics, lower body kinematics, kinematic velocities, and throwing arm joint kinetics during a maximum intent throwing workout. Twenty-six collegiate and professional level baseball pitchers ages 20-30 (mean age 23.5 ± 2.7 years) participated in a pitch velocity and biomechanical evaluation while pitching a series of leather weighted baseballs from a regulation pitching mound. A one-way repeated measures ANOVA was used to evaluate the within-subject effect of ball weight on a total of 15 parameters: pitch velocity, five kinematic positions, four kinematic velocities, and five kinetics. We found that as ball weight increased, pitch velocity, maximum elbow flexion, maximum pelvis rotation velocity, maximum shoulder internal rotation velocity, and maximum elbow extension velocity decreased, while anterior trunk tilt at ball release increased. Training with three- to seven-ounce baseballs can be used to work on increasing pitching velocity without increasing throwing arm joint kinetics or changing pitching mechanics in a practically significant way.
Kinesthetic orientation judgments during later al head, body and trunk tilt
