2000 Volume 4 Issue 2 Pages 116-124
Although many investigations have been done on baseball pitching, there are little information on the wrist and fingers movement during releasing phase. The purposes of this study were to analyze motion of the fingers of the hand and to estimate the forces exerted on the ball by the fingers to increase the ball velocity.
Twelve baseball pitchers were selected as subjects. The movement of their hand and fingers during overarm pitching was videotaped with two high-speed VTR cameras operating at 1000 Hz. Three dimensional coordinates of nine landmarks on the wrist and the second and third fingers and the center of the ball were obtained by a direct linear transformation (DLT) method. Velocities of the ball and the joints of the fingers, joint angles of the finger joints and the force exerted on the ball were calculated. The motion of the hand and fingers were divided into two phases; the first phase begins at the instant of the maximal wrist velocity (WVmax) and ends at the instant of the maximal velocity of the metacarpophalangeae joint (MP) of the third finger (MPVmax), and the second phase was from MPVmax to the ball release (REL).
Four subjects (Group A) of twelve subjects could increase the ball velocity significantly larger than others (Group B) during the second phase. At WVmax, the wrist velocity of Group A was significantly larger than that of Group B (p < 0.05). Although the wrist velocity significantly correlated with the ball velocity at WVmax (r=0.894, p < 0.001), there were no significant correlations at MPVmax and REL. Deceleration of the wrist velocity during the first phase significantly correlated with the increase in the ball velocity during the first phase (r=0.785, p < 0.01). Subjects of Group A flexed their PIP joint more largely than Group B at WVmax, and did not extend so rapidly as Group B. The maximal forces exerted on the ball by the fingers showed significant correlations with the ball velocity at REL (r=0.92, p < 0.001), and subjects of Group A could exert significantly larger force than that of Group B.
These results suggest that the wrist and the finger flexions are important factors to increase the ball velocity just before the ball release, and that the flexed finger joints can exert large force to accelerate the ball and to control the direction of ball projection.
