The present study aimed to identify the features of movement involved in a quick change of backward direction (COD) in response to a light stimulus. Thirteen male soccer players performed the Reactive Agility Test (RAT) involving a light stimulus and sprint running. For this analysis, the players were classified into 2 groups according to RAT time: fast and slow. Sprint time, step parameters, and various kinematic variables were compared between the 2 groups. In terms of sprint time, no significant inter-group difference was observed, but in terms of RAT time, the fast group showed significantly greater speed from 0 to 3 m, from 5 to 13 m including the COD, and from 0 to 13 m, than the slow group. Among step parameters before and after the COD, the fast group showed a significant increase in step frequency before the COD, and the time until the COD foot contact and the time until the lowest point of the velocity of the center of gravity were significantly shorter. In the movements before and after the COD, the fast group tilted the body backwards while maintaining a low center of gravity and performed a recovery action of the swing leg by bending the hip joint of the COD foot in the pre COD phase. In the COD phase, the knee joint of the COD foot was considered the flexion position, and the angular displacement of the knee was small, the body tilting inwards and forwards. Furthermore, the body and the shank tilted forwards in after COD phase. Therefore, it was clarified that deceleration occurred and ended early, and that the movement for deceleration was initiated before COD in order to perform it quickly. The findings of this research can be considered basic knowledge for training in order to improve COD performance and to create new indicators for evaluating it.
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