Document Type


Date of Degree

Spring 2015

Degree Name

PhD (Doctor of Philosophy)

Degree In

Physical Rehabilitation Science

First Advisor

Shields, Richard K

First Committee Member

Cole, Kelly J

Second Committee Member

Cook, Thomas M

Third Committee Member

Grosland, Nicole M

Fourth Committee Member

Law, Laura A Frey


Mechanical loading can modulate tissue plasticity and has potential applications in rehabilitation science and regenerative medicine. To safely and effectively introduce mechanical loads to human cells, tissues, and the entire body, we need to understand the optimal loading environment to promote growth and health. The purpose of this research was 1) to validate a limb vibration and compression system; 2) to determine the effect of limb vibration on neural excitability measured by sub-threshold TMS-conditioned H-reflexes and supra-threshold TMS; 3) to determine changes in center of pressure, muscle activity, and kinematics during a postural task following limb vibration; 4) to determine the effect of vibration on accuracy and long latency responses during a weight bearing visuomotor task.

The major findings of this research are 1) the mechanical system presented in the manuscript can deliver limb vibration and compression reliably, accurate, and safely to human tissue; 2) sub-threshold cortical stimulation reduces the vibration-induced presynaptic inhibition of the H-reflex. This reduction cannot be attributed to an increase in cortical excitability during limb vibration because the MEP remains unchanged with limb vibration; 3) limb vibration altered the soleus and tibialis EMG activity during a postural control task. The vibration-induced increase in muscle activity was associated with unchanged center of pressure variability and reduced center of pressure complexity; 4) healthy individuals were able to accommodate extraneous afferent information due to the vibration interventions They maintained similar levels of accuracy of a visuomotor tracking task and unchanged long latency responses during an unexpected perturbation.

Public Abstract

Mechanical loading, particularly vibration, has recently been incorporated into rehabilitation programs to treat individuals with musculoskeletal and neurodegenerative diseases. Prior research has shown that vibration impacts stem cells, bone, muscle, cartilage, and balance. To safely and effectively introduce mechanical loads to human cells, tissues, and the entire body, we need to understand the optimal loading environment to promote growth and health. The research contained in this manuscript presents a novel device which can safely deliver vibration and compression to a human leg and the impact this system has on the nervous system and movement control. Vibration of the leg changes the excitability of the nervous system and therefore has the potential to be integrated into current treatments for those with nervous system injuries. This type of human limb vibration was also shown to change balance strategies and thus could be incorporated into rehabilitation techniques for individuals at risk for a fall. Finally, vibration offers a novel intervention in which all types of human populations can train movement control strategies and muscle responses geared towards injury prevention. Taken together, vibration has immediate applications in physical therapy and medicine to improve human health.


publicabstract, cortical excitability, H-reflex, long latency reponse, mechanical loading, posture, regenerative


x, 126 pages


Includes bibliographical references (pages 110-126).


Copyright 2015 Colleen Louise McHenry