高齢者の姿勢制御機構について-重心動揺での位置・速度・加速度解析における健康成人との比較から

抄録

The postural control system is considered to be comprised of vestibular, visual and proprioceptive endo-organs. When a person stands on a moving platform, changes of the center of gravity are measured and analyzed as displacements of vertical force on the platform constructed on the strain gauge principle. The vestibular endo-organ perceives the change of head movement and responds to velocity and acceleration of head movement. Also the visual system detects a moving target and responds to velocity. The proprioceptive system responds to changes of displacement of the center of gravity and the distention of the muscle spindles of the calf muscles. Postural control was studied in 48 healthy volunteers and 18 very old subjects with posturography and 20, 40, 60, 80, 100 Hz vibration to the calf muscles, which send misleading signals to the central nervous system. The purpose of this investigation was to determine the kind of postural testing to be used in healthy volunteers and very old persons. The postural control system was analzsed with cumulative recordings of position, velocity and acceleration. Postural control was amazingly stable in healthy subjects. However, variance of velocity and acceleration were greater in very old persons with and without vibration. Postural instability in the elderly was interpreted as a deterioration of many sensory organs : visual, vestibular and proprioceptive endo-organs.
Vestibular endo-organs are well known to be a major part of the control system at times of sudden perturbation, and reciprocal sensory systems are well constituted to keep postural control. It is impossible to explore further which one of these parameters is primarily responsible for postural control and to what degree because of good correlation between velocity and acceleration values. At least in the vestibular system, the acceleration parameter has a major function in posture control.