Document Type


Date of Degree

Spring 2010

Degree Name

PhD (Doctor of Philosophy)

Degree In

Physical Rehabilitation Science

First Advisor

Shields, Richard K

First Committee Member

Cook, Thomas M

Second Committee Member

Darling, Warren

Third Committee Member

Yack, John H

Fourth Committee Member

Fattal, Deema


Approximately 20% of the general population is affected by a vestibular disorder. Vestibular dysfunction is recognized as an important intrinsic factor leading to falls. Despite research on balance strategies with platform perturbations, limited information exists on neuromuscular performance of the knee with perturbations during functional tasks. Improved understanding of the effects of BVL on neuromuscular control of the knee will aid researchers and clinicians in developing rehabilitation programs that address the adaptations and balance deficits that occur with vestibular loss. Hence, the main purpose was to examine accuracy of performance, knee muscle activation patterns and long latency responses in response to unexpected perturbations during a controlled single leg squat in healthy individuals and those with bilateral vestibular loss (BVL).

The first study provided information about the ability to improve performance accuracy with perturbations based on the feedback available. It also showed concomitant changes in the LLR of quadriceps muscles with learning. In the second study, it was found that competent subjects with BVL show similar performance accuracy as healthy individuals during the SLS, with the exception of endpoint error. Muscle strategies are slightly different and vary on firm and foam surfaces. A significant finding was that the LLR is reduced in this group in response to unexpected perturbations, especially when visual feedback is absent. Rehabilitation and/or time living with bilateral vestibular deficiency can lead to a reorganization of the central nervous system, which may partly explain the alterations in neuromuscular control. More research is needed to determine the relationship between the long latency response and fall risk and if different training dosages with perturbations affect these in both healthy and vestibular-deficient populations.


xii, 150 pages


Includes bibliographical references (pages 139-150).


Copyright 2010 Nora Havlik Riley