A Dynamical Systems Analysis of Upright Stance: Exploring the Effect of Unstable Surfaces, Aging, and Pathology
Understanding human balance is a multifaceted problem that is studied by both researchers and clinicians. A decrease in the ability to balance is a predictor for fall risk, which is a major issue for aging and pathological populations. By understanding the underlying mechanisms behind balance deficiencies, we can identify what physiological changes are occurring, and potentially train participants to improve. This thesis focuses on the use of dynamical systems to understand human upright posture, specifically when affected by unstable surfaces, aging, and pathology. First, a literature review is presented that helps emphasize why studying human balance is important. Next, the development of an active balance board with tunable active stiffness and board time-delay is presented. A mathematical model of a person standing on this active balance board is used to simulate results and complete a bifurcation analysis. These theoretical results are used to develop experiments on the active balance board involving young, healthy adults. Next, the differences between young adults and older adults on the active balance board are explored. This includes various analyses of the board angle, as well as an application of principal component analysis to determine movement patterns of participants while on the board. Following this, a novel contact mechanics based posture model is presented to predict behavior during quiet standing due to diabetic neuropathy. Model predictions are validated with experimental results from ten diabetic patients with neuropathy and ten age-matched controls. The thesis concludes with a summary of key findings as well as proposed future work.
Raman, Purdue University.
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