A kinematic study on the volleyball spiking motions in international players : The effective hitting motion on the finger height at the impact and on the ball velocity just after impact

This study was designed to analyze the spiking motions of international players, and to provide these information with clarifying the effective hitting motion on the finger height at impact and on the ball velocity just after impact. Soviet, Cuban, Polish and Japanese male players who participated in the 1981 World Cup Volleyball Games held in Tokyo were filmed at 100 f.p.s. with two 16mm cinecameras during the games. 23 spikings performed successfully were selected for the analysis, and were digitized from the start of the approach run to the end of the swing in the air. 24 three dimensional coordinates for the segment endpoints and the ball were computed by the Direct Linear Transformation Method. The kinematic data were obtained from the 3D coordinates. The results and findings were summarized as follows ; The finger height from the court floor at the impact ranged from 2.93 to 3.33m. The average impact position of the ball was 23cm forward, 27cm right-side, and 54cm above from the center of the head. The heigher impact position seemed to result from the extention of the right arm joints during the forward swing of the spiking. The extension of the right arm joints almost synchronized with flexion of the left arm joints and the extension of the knee joints. This suggested that swinging the left arm and shanks downward should be one of the important motions in increasing the impact position. Peak velocities of the finger, elbow, and shoulder during the forward swing increased nearly twice as much in order of the shoulder, elbow and finger. With the increase in the peak shoulder velocity, the finger velocity at impact increased. The larger peak shoulder velocity seemed to result from the increase in the trunk angular displacement. These results suggested that swinging the trunk forward should be one of the important motions in increasing the finger velocity at impact. On the other hand, the ball velocity just after impact should be influenced by the flight length of the body in the air.The horizontal displacement of CG from the release to the landing ranged from 0.51 to 2.06m. The ratio of the CG velocity at impact to the ball velocity just after impact ranged from 3.9 to 13.7