ABSTRACT
Along with the forward swing of the kicking leg, ball impact is one of the most important factors for fast ball kicking in soccer. Ball impact is a phase during which the players transfer the momentum of their kicking limb to the ball. Through daily training, the players acquire ways to impart the leg and foot momentum into the ball effectively. In most instep kicking, rapid passive motion of the kicking foot occurs due to large ball reaction force during ball contact (Asai et al., 2002; Nunome et al, 2006; Shinkai et al, 2009). To enhance the ball impact efficiency, it has been considered that the magnitude of the foot deformation needs to be minimized by ankle rigidity at ball contact (Asami and Nolte, 1983; Rodano and Tavana, 1993; Lees and Nolan, 1998).
