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Author ORCID Identifier

https://orcid.org/0000-0002-4583-4418

Document Type

Campus-Only Access for Five (5) Years

Degree Name

Doctor of Philosophy (PhD)

Degree Program

Kinesiology

Year Degree Awarded

2019

Month Degree Awarded

September

First Advisor

Richard van Emmerik

Second Advisor

Joe Hamill

Third Advisor

Chris Palmer

Fourth Advisor

Wesley Autio

Subject Categories

Motor Control

Abstract

We examined the role of head movements and orientation and the coordination between lower limb swing movement and body center of mass (COM) during walking while avoiding multiple visual obstacles. The faster we walk the less time there is to interact with or gather new visual information. Therefore, we examined gait speed induced visual information exposure on obstacle avoidance. We examined the effects of constant versus changing walking speeds and systematic increases in gait speed on head reorientation (the Proximal Visual Intersect; PVI) and biphasic vertical accelerations imparted on the head (Harmonic Ratio; HR). Also, how swing foot and body COM coordinated movement towards physical boundaries (Kp) of single stance and boundaries of future anticipated (Ka) foot placements impacted obstacle avoidance. First, we found, when given the opportunity to change speed, individuals slowed down and contacted fewer obstacles. Individuals reoriented their heads downward (smaller PVI) and delayed their swing foot towards the physical boundary (larger Kp) to a greater extent when encountering obstacles compared to no obstacles regardless of walking speed constraints. Secondly, systematic increases in gait speed impacted head orientation, vertical head accelerations and both gait coordination measures. While walking at very fast speeds individuals had the least biphasic vertical accelerations (lower HR). Very fast walking, compared to the two slowest speeds, also delayed the swing foot to the anticipated boundary (larger Ka). These adaptations in head movement and coordination at the very fast speeds resulted in fewer obstacle collisions. Lastly, during walking over visual arrays with increasing obstacle density, when allowed to slow down compared to maintaining a constant speed, individuals avoided the obstacles best by reorienting their heads down (smaller PVI) with more biphasic head accelerations (high HR). This dissertation reveals delaying swing foot early and late in the swing phase towards upcoming “safe” foot placements is beneficial depending on the specific task. Additionally, at faster walking speeds increases in obstacle collision rates are avoided through a decoupling of the head and gait dynamics, as shown by a reduction in the biphasic vertical head accelerations.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

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