Previous studies have reported kinematic coupling between shank and foot segment. However, it remains unclear whether as to kinematic coupling among foot segments. The purpose of this study was to investigate the effects of kinematic coupling between hindfoot and midfoot segments at different modes of run and normal gait. Six healthy young men participated in this study. Subjects were instructed to run (at 2. 5 m/ s) or gait (at 1. 3 m/ s) on the treadmill at speeds set by the examiner. The changes in angles of foot segments during stance phase were calculated based on 3D Foot model. The degree of kinematic coupling between hindfoot and midfoot segments was evaluated by Pearson’s correlation coefficient. Positive correlation indicated the occurrence of the kinematic coupling of pronation of the hindfoot with plantar flexion, pronation and abduction of the midfoot. Similarly, kinematic coupling of supination of the hindfoot with dorsi flexion, supination and adduction of the midfoot were expressed by positive correlation. In running, strong correlations were observed between pronation/supination of hindfoot and three movements of midfoot; 1) plantar/dorsi flexion (r = - 0. 79), 2) pronation/supination (r = 0. 99) and 3) abduction/adduction (r = 0. 85). In gait, the correlation between pronation/supination of hindfoot and plantar/dorsi flexion of midfoot became weak (r = 0. 24). Abnormal responses of the kinematic coupling between the foot segments to changes in modes would be an indicator of dysfunction of the foot segment.
