Age-related Changes in Dynamic Postural Control Ability in the Presence of Sensory Perturbation
For the development of fall prevention programs, the dynamic postural control of elderly persons under conditions when their senses are perturbed needs to be investigated. The present study investigates the manner in which elderly persons respond to external perturbations when their visual and somatic senses are disturbed. The subjects included 4 healthy older adults and 6 young adults. In the experiment, external perturbation was introduced through a platform that was movable in four directions (forward, backward, right, and left). The effects of sensory disturbance created by wearing translucent goggles and standing on a soft floor were examined. The responses were measured in terms of the center of pressure (COP) on the force plate, the electromyographic (EMG) activity, and the joint angle from video analysis. The COP analysis showed that the older group, especially in the presence of sensory disturbances, required a longer time than that for the younger group to return to an erect standing position after external perturbations (recovery time). The EMG indicated that the older group used the articular muscles of the knee to respond to postural perturbations involving up-and-down movements. The recovery time is a characteristic parameter of the response to external perturbations in the presence of sensory disturbances, and thus a potentially useful indicator in evaluating balance ability. The increases in knee muscle’ activities were due to reduced ankle joint torque, which is presumably one of the causes of the prolonged recovery time. These findings could be applied to the development of fall prevention training.