First Advisor

Heise, Gary D.

Second Advisor

Smith, Jeremy D

Document Type

Dissertation

Date Created

7-1-2016

Abstract

In this dissertation, the impacts of increased mass and footwear on walking mechanics and energetics were investigated. In the first study, non-obese individuals were asked to walk on a treadmill with added load to the trunk (~15% of body mass) and with and without shoes. Metabolic costs of walking increased ~12% with added load, but walking barefoot did not significantly change metabolic costs. Trunk loading increased knee and hip range of motion but failed to alter spatiotemporal measures. In study 2, non-obese individuals were asked to complete the same tasks, but this time they walked overground instead of on a treadmill. The focus of this study was on lower extremity kinetics, which were not addressed in the first study. Loading increased stance and double support times, ground reaction forces, and joint moments and powers. Walking barefoot decreased spatiotemporal measures and ground reaction forces, but increased hip and knee moments and powers. Finally, in study three, rather than increasing body mass artificially by adding an external mass to the trunk, obese individuals with BMIs greater than 30 kg∙m-2, but less than 40 kg∙m-2, were recruited. Similar to Study 2, walking barefoot reduced stride length, stance time, and double support time. Barefoot walking also decreased vertical and anteroposterior ground reaction forces. However, joint moment and power responses to footwear conditions were dependent on body morphology, as the Obese and Non-Obese groups responded differently to these footwear conditions. Therefore, footwear condition should be reported and considered when comparing conclusions of multiple studies. Statistical outcomes for kinetic dependent measures also differed with normalization. Four joint kinetic measures (including ankle dorsiflexor and hip extensor moments, and knee and hip powers), were larger in the Non-Obese group than the Obese group after normalization, but did not differ when considered in absolute units. On the other hand, ten joint kinetic measures, including ankle, knee, and hip joint moments and powers, were larger in the Obese group in absolute terms. All ten of these were not different from the Non-Obese group after normalization. Varying normalization schemes partially explains differing outcomes reported in the literature regarding obesity’s impact on gait mechanics. Based on outcomes of the three studies presented here, ground reaction forces appear to scale with total weight, whether this is an external load (Study 2) or a consequence of obesity (Study 3). Walking barefoot decreased stride length, stance time, and double support time and ground reaction forces regardless of loading or obesity. However, joint kinetic responses to footwear appear to be dependent on body morphology, as the Obese and Non-Obese groups responded differently to these conditions.

Keywords

Footwear, Load Carriage, Obesity

Extent

138 pages

Rights Statement

Copyright is held by the author.

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