階段昇降時の床反力特性解析

Abstract

Human motions during steady-state gait have been extensively investigated and their average characteristics are well understood. In recent years, studies of transient gaits, such as initiation and stopping or turning during steady gait, have attracted the interest of some researchers. But most of these studies have been done with level walking. Going up and down stairs is a common activity of daily living. From the mechanical viewpoint, stair gait is quite different from level walking, because the vertical motion of the body is added. A study of the characteristics of the ground reaction forces during stair gait is an important step toward the understanding of the motion of the stair gait. In this study, the characteristics of both the reactions and the points of application during ascending and descending stairs were investigated, and the differences between them are discussed. The initiation and stopping of the stair gait were investigated also. These results are compared with the data on level walking. In experiments, two large force plates and two staircase models composed of five steps were used. Each model had standard dimensions in height and depth for an indoor staircase, and both were set on the large force plate. The results of this study showed many interesting characteristics. In the steady stair gait, the peak-to-peak transition in the longitudinal reaction force diagram was not monotonous, as it is in level walking. The value of the peak in the vertical force diagram was generally larger than that for level walking. It was produced in the double support phase in going up stairs, and in the single support phase in going down stairs. The point of application in the longitudinal direction moved backward once in the single support phase. The reason for this is that the first contact with floor is not the heel but the toe. In the initiation and stopping of the stair gait, the most remarkable characteristics was that the magnitude of the peak of the vertical force component during the first single support phase in initiation differed from that of the last single support phase in stopping. This difference was closely related to the vertical driving and breaking forces, which were produced at the time of initiation and stopping, respectively.