Kinematic and motor variability and stability during gait: effects of age, walking speed and segment height

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Title: Kinematic and motor variability and stability during gait: effects of age, walking speed and segment height
Author: Kang, Hyun Gu, 1978-
Abstract: To understand how falls occur during walking in older adults , we need to understand how the nervous system maintains stability , and how aging affects walking . Four studies were conducted to better understand the effect of age on gait . Older adults display higher gait variability compared to young adults , possibly because of their slower walking . We compared gait stability at multiple controlled walking speeds . Greater gait variability in healthy elderly existed independent of slower walking . Their diminished strength and flexibility partly explained this difference . To explain slower walking in the elderly , some have suggested that muscle weakness and stiffness may force people to walk slower . Others have suggested that people choose to walk slower to be more stable . We compared dynamic stability of gait at multiple speeds . Healthy older adults also exhibited more stability at slower speeds , yet walked at speeds comparable to young adults despite the lower strength and flexibility . Therefore , weakness and stiffness may not force healthy older adults to walk slower . The goal of the nervous system during walking may be to maintain stability of superior segments . We tested whether superior segments are more stable than inferior segments during walking . Superior segments exhibited less orbital stability during preferred walking speed , in contrast to previous suggestions . This highlighted the importance of trunk control during gait . The effects of aging on the fluctuations in the muscle activity during gait are not well understood . We quantified the stride -to -stride fluctuations of EMG as a measure of muscle activation patterns in state -space . Variability increased with speed except in the gastrocnemius . Orbital stability was less in older adults , suggesting that deviations in the EMG amplitude pattern were not readily corrected . Less local stability was seen in older adults , suggesting that older adults were more sensitive to perturbations . Together , these findings suggest that trunk control is important during gait . Strength and flexibility deficits help explain higher variability and lower stability in older adults . Future work will need to address the effect of strength interventions , neurophysiological decline on gait stability and fall risk .
URI: http : / /hdl .handle .net /2152 /3799
Date: 2008-08-29

Citation

Kinematic and motor variability and stability during gait: effects of age, walking speed and segment height. Doctoral dissertation, The University of Texas at Austin. Available electronically from http : / /hdl .handle .net /2152 /3799 .

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