Date of Award

Fall 12-1-2020

Degree Type


Degree Name

Master of Science (MS)


Kinesiology and Health

First Advisor

Feng Yang, Ph.D.


Previous studies have tackled the effect of sole thickness on falls and suggested a significant relationship between the sole thickness and fall risk. However, the prior studies were based on qualitative survey. No quantitative studies have been conducted to closely examine the causal effect of the sole thickness on the risk of falls. The purpose of this cross-sectional study was to explore the effect of the sole thickness on fall risk and the body’s reactions in response to an unexpected slip during stance among young adults. Our overall hypothesis was that thick soles would impair dynamic stability, delay the body’s reactions to the external slip perturbation, and show effective reactional muscle activation. Specifically, I hypothesized that 1) individuals in the groups with thin soles would display greater dynamic stability than the thick groups at recovery step onset and touchdown; 2) the step latency in the thin sole groups would be shorter than the thick groups, contributing to the observed higher stability; and 3) the leg muscles would be activated faster along with a lesser EMG burst in the thin-soled groups than thick-soled groups. Nine young adults aged between 18 and 45 years were recruited and evenly randomized into three groups in terms of the thickness of the sole: barefoot (0 mm), thin (5 mm), and thick (10 mm). After warmup exercise and the familiarization process with the assigned sole, all groups experienced an identical unexpected stance-slip perturbation induced by quickly moving the treadmill belt. Full-body kinematics were collected by a motion capture system and used to calculate the kinematics of the body’s center of mass (COM). Then dynamic gait stability, as the primary outcome measure, was determined based on the COM’s position and velocity relative to the base of support. Other spatiotemporal parameters and electromyography of leg muscles after the slip were the secondary outcome measures, including the recovery step latency, duration, length, slip distance, muscle latency, and the EMG burst. Both the primary and secondary outcomes were compared among groups by using one-way ANOVA followed by appropriate post-hoc tests to test three hypotheses. The results showed instable balance status at the initiation of the recovery step with the thicker soles, changes in spatiotemporal parameters such as a prolonged step latency and duration and larger step length, and a shorter EMG latency and lower EMG burst in TA and GA. This study will advance our understanding of the influence of sole thickness on the risk of falls.


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