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Barnes Udel 0060D 14276.Pdf AN INVESTIGATION OF THE NEUROPLASTICITY UNDERLYING AN IMPROVED REACTIVE BALANCE RESPONSE by Jennifer H Barnes A dissertation submitted to the Faculty of the University of Delaware in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Biomechanics and Movement Science. Summer 2020 © 2020 Jennifer H Barnes All Rights Reserved AN INVESTIGATION OF THE NEUROPLASTICITY UNDERLYING AN IMPROVED REACTIVE BALANCE RESPONSE by Jennifer H Barnes Approved: __________________________________________________________ John J. Jeka, Ph.D. Chair of the Department of Kinesiology and Applied Physiology Approved: __________________________________________________________ Kathleen S. Matt, Ph.D. Dean of the College of Health Sciences Approved: __________________________________________________________ Douglas J. Doren, Ph.D. Interim Vice Provost for Graduate and Professional Education and Dean of the Graduate College I certify that I have read this dissertation and that in my opinion it meets the academic and professional standard required by the University as a dissertation for the degree of Doctor of Philosophy. Signed: __________________________________________________________ Jeremy R. Crenshaw, Ph.D. Professor in charge of dissertation I certify that I have read this dissertation and that in my opinion it meets the academic and professional standard required by the University as a dissertation for the degree of Doctor of Philosophy. Signed: __________________________________________________________ Jonathan R. Wolpaw, M.D. Member of dissertation committee I certify that I have read this dissertation and that in my opinion it meets the academic and professional standard required by the University as a dissertation for the degree of Doctor of Philosophy. Signed: __________________________________________________________ John J. Jeka, Ph.D. Member of dissertation committee I certify that I have read this dissertation and that in my opinion it meets the academic and professional standard required by the University as a dissertation for the degree of Doctor of Philosophy. Signed: __________________________________________________________ Christopher A. Knight, Ph.D. Member of dissertation committee ACKNOWLEDGMENTS Special thanks go to the following individuals: Dr. Jeremy Crenshaw for serving as my academic advisor, for always being encouraging and supportive, and for providing insightful advice and direction. Dr. Jonathan Wolpaw for serving as my scientific advisor and for providing both the guidance and resources needed for conducting this research. Dr. Jonathan Carp for sharing his scientific expertise. Drs. John Jeka and Christopher Knight for taking the time to serve on my committee. Dr. Amir Eftekhar, Mr. Timothy Fake, and Mr. Steve Carmack for their technological support in hardware and software development. My incredible research assistants: Ms. Susan Heckman, Ms. Allegra Wu, Ms. Kelly Fitzpatrick, for help with data collection; and importantly Dr. Edward Greenberg for assistance with data collection and processing throughout the entire project – thank you Ed, for your steadfast commitment! This manuscript is dedicated to my family, especially my husband Joe and daughters Anja and Marissa. Thank you for your unwavering love, support, patience, and encouragement – you are the best!! iv TABLE OF CONTENTS LIST OF TABLES ...................................................................................................... viii LIST OF FIGURES ....................................................................................................... ix ABSTRACT .................................................................................................................. xi Chapter 1 INTRODUCTION .............................................................................................. 1 1.1 Overview ................................................................................................... 1 1.2 Specific Aims and Hypotheses .................................................................. 5 1.3 Significance and Innovation ...................................................................... 7 2 AIM 1: THE EFFECT OF TRAINING ON PERFORMANCE OF A NON- STEPPING RESPONSE TO POSTERIOR SURFACE TRANSLATIONS ... 11 2.1 Introduction ............................................................................................. 11 2.2 Methods ................................................................................................... 14 2.2.1 Participants .................................................................................. 14 2.2.2 Protocol ....................................................................................... 14 2.2.3 Data Collection and Processing .................................................. 20 2.3 Results ..................................................................................................... 21 2.4 Additional Analyses ................................................................................ 24 2.4.1 Effect of Displacement Range on Outcome ................................ 25 2.4.2 Effect of Baseline Stepping Threshold on Outcome ................... 26 2.4.3 Effect of Age on Stepping Threshold .......................................... 27 2.5 Discussion ............................................................................................... 29 2.6 Additional Applications .......................................................................... 30 3 AIM 2: THE EFFECT OF TRAINING A NON-STEPPING RESPONSE TO POSTERIOR SURFACE TRANSLATIONS ON THE SOLEUS H- REFLEX ........................................................................................................... 32 3.1 Introduction ............................................................................................. 32 v 3.1.1 Short-term and Long-term Adaptation of the Soleus H-reflex ... 34 3.1.2 Perturbation-based Reactive Balance Training and the Soleus H-reflex ....................................................................................... 39 3.2 Methods ................................................................................................... 42 3.2.1 Participants .................................................................................. 42 3.2.2 Protocol ....................................................................................... 43 3.2.3 Data Collection and Processing .................................................. 46 3.3 Results ..................................................................................................... 48 3.3.1 Effect of Reactive Balance Training on the Soleus H-reflex ...... 48 3.3.2 Correlation between Change in Stepping Threshold and Change in Soleus H-reflex Behavior ........................................... 52 3.4 Additional Analyses ................................................................................ 54 3.4.1 Effect of Baseline H-max/M-max on Change in H-reflex Control Trial Amplitude .............................................................. 55 3.4.2 Effect of Baseline H-max/M-max on Baseline Stepping Threshold ..................................................................................... 56 3.5 Discussion ............................................................................................... 58 3.5.1 Differences in the Direction of H-reflex Change ........................ 59 3.5.2 Between-leg Differences in H-reflex Behavior ........................... 64 3.6 Conclusions ............................................................................................. 67 3.7 Limitations and Future Directions .......................................................... 67 4 AIM 3: THE EFFECT OF TRAINING A NON-STEPPING RESPONSE TO POSTERIOR SURFACE TRANSLATIONS ON POSTURAL STEADINESS .................................................................................................. 70 4.1 Introduction ............................................................................................. 70 4.2 Methods ................................................................................................... 74 4.2.1 Participants .................................................................................. 74 4.2.2 Protocol ....................................................................................... 74 4.2.3 Data Collection and Processing .................................................. 76 4.3 Results ..................................................................................................... 78 4.3.1 Effect of Reactive Balance Training on Postural Steadiness ...... 78 vi 4.3.2 Correlation between Change in Postural Steadiness and Change in Soleus H-reflex Behavior ........................................... 80 4.4 Additional Analyses ................................................................................ 84 4.5 Discussion ............................................................................................... 86 4.6 Conclusions ............................................................................................. 89 4.7 Limitations and Future Directions .......................................................... 90 5 SUMMARY ..................................................................................................... 93 5.1 Summary of Results ................................................................................ 93 5.2 Important Remaining Questions ............................................................
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