2016 Volume 5 Pages 13-18
In this study, balancing capability in the longitudinal direction during rising from the seated position in the elderly was evaluated. In particular, the influence of the rising speed at the moment of leaving the seat, referred to as “seat-off,” on balancing capability was examined, since it affects the occurrence of falls. Twenty-eight elderly individuals participated in the study. They were divided into two groups based on their past experience of falls: 19 in the stable rising group and 9 in the unstable rising group. Body movement and the corresponding ground reaction forces during rising motion were measured at two different speeds in each subject, using a motion capture system and a force plate, respectively. From the measurements, “seat-off parameters” that characterize the seat-off motion were obtained. Seat-off parameter values in the stable and unstable rising groups were distributed separately in the seat-off parameter space, forming two distinct clusters. The cluster for the unstable rising group could be further divided into two sub-clusters. The results imply two types of instability during rising from seated position: instability in the forward direction and instability in the backward direction.