ABSTRACT

　We investigated the finger forces and kinematics during overarm throwing of balls with two different textures, from the perspective of the sensorimotor control of dexterous throwing. Five males threw two different balls, one with a smooth silk surface and the other with a sandpaper surface, at a target located 2.7m away as accurately as possible. The force of the middle finger was measured using a three-dimensional force transducer at a frequency of 2kHz. The kinematics were recorded using eight motion-capture cameras at 500Hz. Ball texture did not affect the ball velocity, range of wrist movement, or peak resultant force. However, the peak shear force and range of elbow movement were significantly smaller with the silk ball than the sandpaper ball. The resultant and shear forces had two peaks before the ball release. The first peak of the resultant force corresponded to the timing of maximal wrist dorsiflexion, 100ms before the ball was released, suggesting that this force during the first half of the forward swing is the propulsive force that imparts the ball velocity. The second peak, 30ms before the ball was released, roughly corresponded to the time when the hand passed the wrist in the direction of the throw, suggesting that this force contributed to the spin of the ball. In addition, the ball texture affected the shear force acting on the ball.

DESCENTE SPORTS SCIENCE Vol.38/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE