Evaluation of body balance system using postural sway data

Abstract

This thesis is concerned with the evaluation and understanding of the static performance of postural control system. A computer-aided instrumentation system for the automatic measurement of postural sway has been developed. We used only the Kistler force platform and amplifiers, and developed the data acquisition and analysis software using an IBM PC. This system was used to obtain the continuous records of center of pressure location. Also, an attempt was made to determine the effect of respiration on standing balance. Ten able-bodied subjects were asked to stand upright on a force platform and were asked to hold their breath after inspiration and after expiration, and to breathe regularly, 4, 6, and 8 respirations per 20 seconds. Sway was measured over 20-second periods with eyes open and eyes closed. The results show that both respiration and eye condition affect the sway distance of the center of pressure on body balance. The sway distance in holding breath after inspiration is significantly greater than in holding breath after expiration, and increasing the respiration rate produces a greater postural sway. Also, the grade of visual compensation for body balance is higher in the regular respiration condition than in breath holding. Finally, this thesis is concerned with the contour representation and analysis of postural sway trajectory in posturography. We proposed two methodologies to derive the contour of postural sway based on the boundary points of sway area. An algorithm for finding the sway contour in each method was developed, and the experiments were performed to examine the computational efficiency between the methods proposed. Fourteen able-bodied men were asked to stand upright on a force platform to compare the numerical measures of sway shape with other quantitative sway measures used in previous researches into balance. The results show that numerical measures of sway contour (area, perimeter, and complexity of sway shape) and radius leng...