Date of Award

Summer 8-2023

Document Type


Degree Name

Doctor of Philosophy (PhD)


Rehabilitation Sciences


Kinesiology and Rehabilitation

Committee Director

Steven Morrison

Committee Member

Daniel M. Russell

Committee Member

Anastasia Raymer


The purpose of this work was to study the age effects on average performance and variability of movement responses in children, young adults, and older adults across multiple motor tasks. Optimal motor performance is observed in healthy young adults with declines observed at either end of the lifespan. This pattern has been represented as a U-shaped/inverted U-shaped curve. Little is known about if this pattern persists in chewing dynamics. While chewing has been found to improve aspects of attention, a cognitive function, research is limited on the relationship between chewing and other motor tasks.

The first aim of this research was to conduct a scoping systematic review to identify what measures of variability are reported for preferred performance of chewing and walking in children, young adults, and older adults and the age-related differences across these age groups. The available research was insufficient across these groups and does not support the perspective that children and older adults are more variable than young adults.

The second aim was to examine age-related differences in averages and variability of chewing, reaction time, balance, and walking responses across children, young adults, and older adults. A U-shaped curve was revealed for reaction time and postural sway with the young adults producing faster reaction times and decreased postural sway than the children and older adults. Chewing rates followed a similar curve but with children chewing at faster rates than young and older adults. No age-related differences were observed for normalized gait speed.

The final aim was to examine dual task relationships between chewing and secondary motor tasks in children. Sixteen healthy children completed finger tapping, reaction time, and walking while chewing at different speeds. Chewing rates varied when produced with a secondary motor task and the secondary motor tasks were differentially influenced by chewing. Reaction times slowed during chewing while walking rates increased/decreased with changes in chewing rates. This relationship was not as strong as previous reports in adults.

Overall, the anticipated patterns across the age groups were only partially revealed within this work. Understanding normal movement patterns is the foundation to identifying variations in atypical populations.


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