A Study of Control Mechanism for of Standing-up Achieving a Motion Task

Biomechanical Motion Analysis of Standing-up

Abstract

The purpose of this study was to identify the control mechanism of changing movement of the body's center of mass (CM) during standing up from a chair. One of the requirements of stand-up motion from a chair is that the movement of the CM must be controlled from forward horizontal direction to upward vertical direction, in order to secure upright balance at the termination of the standing. The CM trajectory and velocity for stand-up motion were computed at three movement speeds (natural, fast, and slow) by a motion analysis system (VICON). Eleven events were identified in each trial. The main events were the time of the peak propulsive power and the peak braking power, the time of the peak horizontal component of the CM velocity occurrnce, and the time from the beginning to the completion the body losing contact with the seat. The timing and sequence of these events were investigated. The results showed that the peak propulsive power in the slow speed group had the earliest timing and in the fast group had the latest at the beginning and at the completion of the body losing contact with the seat. There were statistical significant differences in the sequential times compared with the other group of events. The feature of the timing of events suggests that the control mechanism of changing movement of the CM is produced by the braking power progressively increasing before the time the subject leaves the seat. The timing of these events varied with the conditions of standing up from the chair.