スチュワートプラットフォーム型短下肢装具を用いた歩行中の内反摂動からのバランス回復動作に関する研究

抄録

According to a survey by WHO, approximately one third of elderly persons aged 65 or above experience one or more falls every year, and the falls cause serious injuries. One of the risk factors for falls is impairment of the balance control function that is necessary to recover from perturbations during gait. Several previous studies have analyzed the motion of recovering from perturbations in the anteroposterior direction during gait to prevent human fall. For example, one method was to introduce an obstacle suddenly while walking during a treadmill test, and to suddenly stop the belt of the treadmill during gait. However, as these methods do not introduce perturbation to lose balance sideways (in frontal plane) during gait, the reactive balance control motion of recovering from an inversion perturbation remains unclear. In the present study, we investigated the differences in the reactive balance control motions to recover from perturbations in the anteroposterior direction and those to recover from perturbations in the mediolateral direction, using an ankle foot orthosis that we developed. The orthosis can reproduce the input motions of the ankle joint in six degrees of freedom by controlling six pneumatic cylinders simultaneously. We investigated the pattern of recovery motion from inversion perturbation during gait while the subject walked with the orthosis on a treadmill. In this experiment, the orthosis randomly increased the power of the subject's right ankle joint in the inversion direction during the right loading response phase as attempt to introduce inversion perturbation. The results of this experiment demonstrated that there were significant differences between the width of a non-perturbed step and the width of the step after inversion perturbation. On the other hand, the patterns of step length and step time after inversion perturbation were similar to those after anteroposterior perturbation during gait. The results also showed that there were significant differences between muscle activities (gastrocnemius, tibialis anterior, biceps femoris and rectus femoris) after perturbation in the anteroposterior direction and those in the mediolateral perturbation during gait.