Comparison of feet shapes during gait between low group and normal group of medial longitudinal arch

Abstract We classified the subjects into the normal arch group and the lower arch group, and compared the configuration changes of medial longitudinal arch as well as the ground reaction forces during gait movement. As for the subjects, which numbered 12 in total, the low arch group was composed of 6 legs of 3 persons and the normal arch group was also composed of 6 legs of 3 persons. We measured the configuration of arch and the ground reaction force during gait movement at the time of heel strike, foot-flat, mid-stance, heel-off, and toe-off and compared them. For the medial longitudinal arch, the changes of the medial arch angle were line connecting between the medial heel and the navicular bone and navicular bone and the first metatarsal head. Two units of high-speed cameras were used to measure this angle. Also measured with two force plates were the ground reaction force applied to the hind foot and the ground reaction force applied to the forefoot. As compared between the normal arch group and the low arch group, the average change of the medial arch angle in the low arch group during the time from the mid-stance to the heel-off was found to be 0.5i, which was smaller than that of the normal arch group. From the measured force components using force plates, it appears that the low arch group, having lost the spring stiffness of the foot, is unable to make forward smoothly.