サッカーのゴールキーパーにおけるダイビング動作の力発揮特性

抄録

It is believed that the success of the goalkeeper (GK) in saving difficult shots by diving is a key factor in soccer because it can influence the outcome of the game to a large extent. However, the most appropriate way to exert force during the diving motion according to the course of the shot from either leg is still unclear. Therefore, the purpose of this study was to clarify the fundamental mechanism of a GK's diving motion according to the height and distance of the shot. We performed an experiment in which 11 university GKs participated. They were asked to dive toward balls set at 3 different heights located a short or a long distance from the GK. By examining the GKs' diving motions, we calculated the ground reaction force (GRF), joint angular velocity, and joint torque. The results indicated that the magnitude of the GRF under both legs and the direction of the GRF under the ball-side (BS) leg differed with the ball height. We also found that a higher dive by the GKs corresponded to a larger counter-movement of the contralateral-side (CS) leg and a higher stopping power of the BS leg in order to increase the vertical velocity, and more exertion of extension torques at the hip and foot for takeoff compared to those in lower dives. Furthermore, a lower dive of the GKs corresponded to a larger angular impulse of the BS hip adduction after the BS leg touched the ground. These findings suggest that during the takeoff part of the diving motion of a GK, depending on the ball height, the CS leg controls the magnitude of power and the BS leg controls both the magnitude and the direction of power in order for the GK to dive directly towards the ball.