バレーボールのスパイク技術に関する研究 : 高く飛ぶための踏切技術について
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A study on volleyball spike-motion with respect to take off technique for height
The purpose of this study was to kinematically investigate the spiking motions of international-class players and to collect the informations of take off technique for height. 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 successfully performed spikings were selected for the analysis, and were digitized from the start of the approach run to the end of the swing in the air. 21 three dimensional coordinates for the segment endpoints were computed by the Direct Linear Transformation Method. Various kinematic parameters were obtained from the 3D coordinates. The results and findings were summarized as follows : 1) The locations and directions of the CG pathways were different from player to player (Fig.1). Therefore, 3D frame of reference during the take off phase was specified, where Y axis represented forward-backward directions, and the origin of the coorinate system was the point on the court floor which CG located at the end of former half. Averaged take off motion of 23 spikings was obtained by the normalization and averaging of the displacement data for 21 segment endpoints (Fig.2). The motion seemed to represent the take off technique for height, because the analyzed spikings were successfully performed spikings by internationa-class players. 2)Jumping height ranged 73-97cm, and significantly correlated with the CG height from the release to the maximum point in the air (H2). The decrease in vertical velocity of CG before the release almost synchronized with the extension of the ankle joints (Fig.3). This may suggest that H2 can be increased by the powerful extension of the ankle joints. The backward lean angle at the touch down and the angular displacements of the hip, knee and ankle joints during the take off significantly correlated with the vertical displacement of CG (Fig.4). This suggested that learning the body backward and extending the range of leg-joint motion should be one of the important motions in increasing H2.