Date of Award

Spring 2013

Document Type


Degree Name

Doctor of Philosophy (PhD)


Human Movement Sciences


Human Movement Sciences

Committee Director

Steven Morrison

Committee Director

Bonnie Van Lunen

Committee Member

Daniel M. Russell

Committee Member

Sheri R. Colberg


The aim of this study was to examine changes in postural and locomotor control under varying task demands. Three experiments were designed to address the impact that fast walking had on standing posture over time, slow walking had on gait dynamics over time, and the extent to which gait speed interacts with the ability to walk randomly.

For experiment I, the aim was to identify the time course in which postural adaptation occurred while walking at faster than preferred speeds. Postural motion was assessed at specific intervals over a 35-min walking trial. Findings revealed that walking at a faster speed increased the amount, variability, and structure (Approximate Entropy-ApEn) of postural motion compared to baseline assessments. Subsequent trials following baseline assessments revealed a leveling-off for specific center of pressure (COP) variables and decline in path length, although heart rate (HR) and rate of perceived exertion (RPE) increased over the entire walking trial.

In experiment II, the aim was to examine changes in stride-to-stride variability over time while walking at slower than preferred speeds. The results revealed an increased stride-to-stride variability and signal regularity (lower ApEn) during walking at 80% preferred walking speed (PWS) compared to PWS. After 10-15 mins a decrease stride-to-stride variability and increase in signal irregularity was seen. Changes leveled-off for the remainder of the session.

Experiment III was designed to examine the effect that intentionally increasing variability (random) had on gait dynamics. Participants were asked to vary their gait while walking on a treadmill at three different speeds. The results revealed gait speed was a significant factor in the amount of variability (CV, range), with higher levels produced during the slower speed than at PWS and the faster speed. Higher levels of complexity (higher SampEn) were seen in stride time and knee joint motion during the random condition irrespective of gait speed.

Overall, young adults are able to walk at speeds faster or slower than preferred as well as increase gait variability when instructed. These changes in postural and locomotor dynamics reveal that a healthy motor control system can quickly adapt to the task demands imposed upon it.


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