A Critical Interpersonal Distance Switches between Two Coordination Modes in Kendo Matches

In many competitive sports, players need to quickly and continuously execute movements that co-adapt to various movements executed by their opponents and physical objects. In a martial art such as kendo, players must be able to skillfully change interpersonal distance in order to win. However, very little information about the task and expertise properties of the maneuvers affecting interpersonal distance is available. This study investigated behavioral dynamics underlying opponent tasks by analyzing changes in interpersonal distance made by expert players in kendo matches. Analysis of preferred interpersonal distances indicated that players tended to step toward and away from their opponents based on two distances. The most preferred distance enabled the players to execute both striking and defensive movements immediately. The relative phase analysis of the velocities at which players executed steps toward and away revealed that players developed anti-phase synchronizations at near distances to maintain safe distances from their opponents. Alternatively, players shifted to in-phase synchronization to approach their opponents from far distances. This abrupt phase-transition phenomenon constitutes a characteristic bifurcation dynamics that regularly and instantaneously occurs between in- and anti-phase synchronizations at a critical interpersonal distance. These dynamics are profoundly affected by the task constraints of kendo and the physical constraints of the players. Thus, the current study identifies the clear behavioral dynamics that emerge in a sport setting.在诸多竞技体育运动中，运动员需快速且持续地做出动作，以适配对手与赛场实体对象所作出的各类动作。在剑道（kendo）这类格斗武术中，运动员需熟练调整人际距离以取胜。然而，目前关于影响人际距离的战术动作及其专业属性的相关研究资料仍十分匮乏。本研究通过分析剑道比赛中专业运动员的人际距离变化，探究了对抗任务背后的行为动力学机制。对偏好人际距离的分析显示，运动员会根据两种距离阈值，向对手靠近或远离。最受偏好的距离可让运动员即时完成击打与防守动作。对运动员靠近与远离动作的速度进行相对相位分析（relative phase analysis）后发现，运动员在近距离时会形成反相同步（anti-phase synchronization）模式，以与对手保持安全距离。而在远距离时，运动员则切换为同相同步（in-phase synchronization）模式以接近对手。这种突发的相位转换现象，是一种典型的分岔动力学（bifurcation dynamics）特征：在临界人际距离处，同步模式会在同相与反相之间规律性地瞬时切换。上述动力学机制深受剑道的任务约束与运动员自身生理约束的显著影响。因此，本研究明确了竞技体育场景中涌现出的清晰行为动力学模式。