Enhancing posturography stabilization analysis and limits of stability assessment

Date of Award

2016

Degree Name

Ph.D. in Mechanical Engineering

Department

Department of Mechanical and Aerospace Engineering

Advisor/Chair

Advisor: Kimberly E. Bigelow

Abstract

Posturography is the study of an individual's regulation of balance and much posturography research is dedicated to studying the effect of aging on postural control. The study of the postural stability of this population is motivated by a need to understand physiological changes caused by the aging process in older adults. While posturography is commonly used in research with older adults, there is need to improve and enhance current data collection procedures and data analysis approaches. This work identified and addressed four research gaps in current posturography knowledge with an emphasis on older adult populations. A single session of data collection was conducted to obtain the necessary data for each aim which were then each addressed independently. Ninety older adults participated in this research. The objective of the first aim was to evaluate use of Time to Stabilization method to gauge the stabilization time for older adults stepping onto a firm and a compliant surface, with an emphasis on first identifying methods to assess the appropriateness of the data trend and to determine the success of the curve fit. The results of this study suggest the majority of older adult data is appropriate for this analysis. The authors suggest using a signal-to-noise cutoff of 2.5 when evaluating data trends and a R2 cutoff of .25 when evaluating curve fit. The objective of the second aim was to determine if incorporating a foam surface, nonlinear analysis, and age stratification would improve the insightfulness of the Limits of Stability (LOS) assessment. The findings of this work indicated differences in LOS performance between age groups and that the assessment benefits from nonlinear analysis. The objective of the third aim was to determine whether LOS assessment inertial measurement unit (IMU)-based outcome measures demonstrated greater differences between fallers and non-fallers than the traditional center of pressure (COP)-based outcome measures. The results showed the IMU-based measure of jerk was better than the tradition posturography measures at differentiating between fallers and nonfallers. The final aim's objective was to assess the degree of correlation between both sensors to evaluate whether the older adults in this study performed the LOS assessment correctly. Results indicated participants moved with a moderately high degree of correlation in the M/L plane but less in the A/P plane. This raises questions regarding implementation of the LOS assessment as it appears the ankle strategy is not being fully adhered to, especially in the A/P plane. Study limitations include only a single curve fitting method was explored, signal-to-noise ratio and R2 values were the only two metrics by which the data trend and curve fit were evaluated, falls were self-reported, and sensor positioning. Future work includes a study evaluating two clinical groups could utilize the time to stabilization method and jerk measures and a study to explore the fact that participants who visually appear to be correctly conducting the LOS assessment actually display a wide range of correlation between upper and lower body segments.

Keywords

Posture, Older people Orientation and mobility, Human beings Attitude and movement, Mechanical Engineering, Biomechanics, biomechanical engineering, fall prevention, sample entropy, stabilize, wearable sensors, jerk

Rights Statement

Copyright © 2016, author

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