Document Type


Date of Degree

Fall 2016

Access Restrictions


Degree Name

PhD (Doctor of Philosophy)

Degree In

Physical Rehabilitation Science

First Advisor

Shields, Richard K

First Committee Member

Casey, Darren

Second Committee Member

DeJong, Stacey

Third Committee Member

Frey Law, Laura

Fourth Committee Member

Gutmann, Laurie


Injury occurs when people are exposed to an unexpected event. There is a knowledge gap regarding whether people can learn to respond to unexpected events and whether this learning is moderated by age, physical activity level, cognitive function, and motor cortical excitability. The purpose of this research was to examine the influence of: 1) age, 2) physical activity, 3) cognitive function, and 4) motor cortical excitability on motor performance and learning during a novel visual motor task of the wrist.

The major outcomes of this research revealed that the ability to respond to unexpected events is reduced with age; however, with practice, older people retain the capacity to learn to respond to unexpected events. This work also demonstrates that elderly people use both feed-forward and feedback strategies to improve their response to unexpected events. Conversely, young people predominantly use a feed-forward strategy to improve their ability to respond to an unexpected event. Importantly, active older people show greater capacity to respond to unexpected events and to learn to improve responses than less active older people. Older people with higher cognitive function demonstrate a greater capacity to respond to unexpected events than those with lower cognitive function. Furthermore, merely increasing motor cortex excitability does not translate into improved performance after young people have learned a motor task. Taken together, age, physical activity, and cognitive function impact human performance and the capacity to learn to respond to unexpected events. These findings have important implications as to how to rehabilitate and/or prevent injury to unexpected events in older people.


xiii, 147 pages


Includes bibliographical references (pages 137-147).


Copyright © 2016 Chu-Ling Yen