Date of Award

Summer 8-2016

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Rehabilitation Sciences

Program/Concentration

Kinesiology and Rehabilitation

Committee Director

Heather M. Hamilton

Committee Member

Hunter J. Bennett

Committee Member

Patrick B. Wilson

Abstract

Aging is accompanied by slower walking speed and higher metabolic cost of walking (MCoW), yet the mechanisms linking coordination and efficiency across the adult lifespan remain poorly understood. This dissertation examined how lower extremity coordination, sequencing of leg forces during the step-to-step transition (STST), and the relationship between leg forces sequencing during STST and MCoW differ with age and relate to MCoW in healthy young, middle-aged, and older adults across different walking speeds. Guided by a dynamical systems framework, age-related gait patterns were viewed as movement solutions that emerge from changing organismic constraints rather than as a failed version of young-adult gait.

In Study 1, a gait phase normalization method and continuous relative phase analysis were used to compare intra- and interlimb coordination at participants’ preferred walking speed (PWS). Age-related differences were not uniform across the gait cycle. They were concentrated around the STST, where older adults exhibited altered coordination timing compared to younger adults.

In Study 2, the Sequence (S) index, a measure of overlap between push-off and collision forces during walking gait, was evaluated as a marker of STST mechanical efficiency across speeds scaled to PWS. Older adults showed consistently higher S index values compared to young adults, driven by both altered timing and reduced single-support impulses, indicating greater cancellation of positive and negative work during STST among older adults.

In Study 3, the relationship between S index and MCoW was examined in young, middle-aged, and older adults walking at 80%, 100%, and 120% of PWS. Older adults exhibited higher S index values and higher MCoW than both young and middle-aged adults. Higher S index predicted greater MCoW during slow walking, but this relationship was not significant at PWS or during fast walking. The S index–MCoW relationship did not differ significantly among age groups.

Together, these findings further characterize age-related differences in STST by showing that they are expressed through phase-specific coordination timing and differences in the sequencing of push-off and collision forces. They also provide condition-specific evidence relating STST mechanical efficiency to MCoW, with a significant relationship between S index and MCoW during slow walking but not at preferred or fast speeds. The S index may therefore be useful for characterizing STST coordination and evaluating interventions intended to improve walking economy, particularly during slow walking; however, experimental studies are needed to explore clinical applications of these findings.

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DOI

10.25777/rheh-gw04

ISBN

9798193214519

ORCID

0000-0002-9751-7094

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