Postural Responses under the Gradually Increasing Horizontal Perturbation

Abstract

It is important to consider a measurement and an evaluation of the postural responses in human to perturbation such as trips or slips. In this study we gave healthy young subjects backward translation of table as horizontal perturbation, and measured the body sway by the perturbation. The sixteen subjects attached the sensor to an ankle joint, a thigh and a back near the center of gravity. They are kept upright position on the table and then given the perturbation. The experiments were performed with 20 trials of different acceleration from 0.6m/s² to 4.4m/s² by 0.2m/s² in gradually increase. As a result, it was classified in three patterns about a process they shifted from an ankle strategy to a stepping strategy by the peak value of the angular velocity, when they are given the perturbation sequentially. It is no correspondence relationship between classified shift process, static balance inspection and perturbation that begin to support by a stepping strategy. The experiment performed with perturbation in gradually increase identified that postural sway increased with magnitude of perturbation and postural strategy shifted gradually. Therefore it suggested that the experiment performed with perturbation in ascending order was useful to see the gradualshift process unlike with the experiment performed randomly.