立位人体の強制振動に対する同期的な応答の解析

抄録

Assessment and improvement of balance ability is an important issue in the medical field. The balance ability should be divided into static balance ability and dynamic balance ability, and it is necessary to notice the dynamic balance ability from the viewpoint of fall prevention. To check the dynamic balance ability, there is a method of single frequency oscillation of support surface on sagittal plane. The response of steady-state oscillation was obtained when the support surface swayed around 0.6-1.0 Hz. The purpose of this study is to clarify the control objective in the balance control. We focused on the joint strategies and defined modal coordinates to discriminate between the ankle joint strategy mode and the hip joint strategy mode. Experimental results showed that amplitude of head in world coordinate was almost zero and the hip joint strategy mode was much smaller than the ankle joint strategy mode. To explain the motion in theory, we calculated the stationary solution on the basis of a hypothesis that ankle joint strategy is dominant in the motion. From the experimental result, we found that the theoretical solution coincided with experimental result. This indicates that balance control under single frequency oscillation of support surface around 0.7Hz is dominated by ankle joint strategy.