How to use exoskeletons to improve self-selected walking speed in older adults

Older adults are becoming the majority population across the globe and as we age quality of life and ability to live on our own declines. Self-selected walking speed is highly correlated with these declining traits and slows with age. The reason for slowing walking speed with age is unknown. Exoskeletons tested in younger adults have shown success to increase walking speed, decrease energetic consumption, and affect biomechanics across the lower limb, presenting an opportunity to understand more about walking speed. In this work, we (1) apply ankle neuromuscular model-based control to investigate the effects of exoskeleton assistance on user target joint neuromechanics, (2) optimize impedance control at the hip to reduce metabolic cost across walking speeds, (2) optimize hip and ankle assistance profiles independently to increase overground self-selected walking speed, and (4) determine if/how older adults are optimally selecting their walking speed. This work has contributed to understanding the effects of various exoskeleton control strategies at the hip and ankle on user energetics and neuromechanics during walking. In Chapter 2, we discuss how neuromuscular model-based control at the ankle may not benefit walking metabolic cost but increase total torque production and decrease user moment. In Chapter 3, we demonstrate how impedance torque mimicking a semi-active device applied to the hip can provide metabolic benefits and how these are driven by local muscle activity changes. In Chapters 4 and 5, we apply a novel torque optimization strategy to increase SSWS in younger and older adults to (4) understand the important mechanical characteristics of assistance to increase walking speed and (5) understand the physiological drivers of walking speed selection.

Date

2023-11-13

Resource Type

Text

Resource Subtype

Dissertation

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