Muscle Structure and Function in Older Adults with a Rotator
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MUSCLE STRUCTURE AND FUNCTION IN OLDER ADULTS WITH A ROTATOR CUFF TEAR BY MEGHAN ELISE VIDT A Dissertation submitted to the Graduate Faculty of WAKE FOREST UNIVERSITY GRADUATE SCHOOL OF ARTS AND SCIENCES In Partial Fulfillment of the Requirements for the Degree of DOCTOR OF PHILOSOPHY Biomedical Engineering May 2014 Winston-Salem, North Carolina Approved By: Katherine R. Saul, Ph.D., Advisor, Chair Thomas L. Smith, Ph.D. Anthony P. Marsh, Ph.D. Michael L. Madigan, Ph.D. Jessica L. Sparks, Ph.D. ACKNOWLEDGEMENTS There is an African proverb that states “it takes a village to raise a child” and the same holds true for graduate students. The work and achievements I have accomplished over the past several years would not have been possible if it were not for the support and devotion of several people. First and foremost, my advisor, Kate. When I first learned of your lab and research activities, I honestly had no idea what most of it was. I was eager to go back to school, so I took a huge leap of faith and joined your lab. And I am so glad that I did! There have certainly been some adventures throughout the years, like when travelling to conferences and to meet with collaborators, as well as the highs and lows with the passage of various life events. You have pushed me to explore questions from various angles, become independent yet collaborative, and to take chances. I have grown as a researcher and as a person under your tutelage. It has been quite a journey! Thank you for all of your support and instruction throughout the years and for taking a chance on me as your first recruited student for the lab. My NRSA Sponsors, Kate, Dr. Marsh, and Dr. Hegedus. You all have been fantastic. I have enjoyed having bi-monthly meetings to discuss my project and how the data is coming together. This has been such a positive experience for me. Your genuine interest in not only the research at hand but my academic and professional development has truly meant a great deal to me. You have challenged me to think critically, defend my conclusions, and be creative. I have the utmost respect for each of you as people, researchers, and clinicians, and I am so grateful for your guidance. Thank you, thank you, thank you. ii To the rest of my committee, Dr. Smith, Dr. Marsh, Dr. Madigan, and Dr. Sparks. Thank you for your willingness to serve on my examination committee. Your insightful thoughts and comments have played a fundamental role in shaping the study and the way I have approached this project. Your different areas of expertise have helped me learn to “take a step back” and consider research from different points of view. Thank you for your time and effort. The Department of Orthopaedics, Dr. Beth Smith, Dr. Tuohy, Dr. Poehling, Dr. Freehill, and all of your support staff. I have truly enjoyed collaborating with you on this project. Your willingness to allow me to shadow in the clinic and the O.R. has provided academic enrichment, and such a great excuse to leave the lab once in a while! It is rare to have the chance to learn from some of the best people in the field, and I am very grateful to have had the opportunity to learn from you. Thank you for being such patient and enthusiastic teachers. Statistical guidance from Dr. Miller. I am appreciative for your patience with me and my myriad of questions. Your work with statistical designs and analysis has been an integral component of this work. I am grateful for all of your effort and your commitment to my educational endeavors and this project. Subjects from the community. Without your willingness to participate in these research studies, I wouldn’t have any data for this dissertation. Thank you for being generous with your time. You were all so pleasant to chat with during the testing sessions, and I am thankful to each of you who participated. Previous and current labmates, Melissa Daly, Dustin Crouch, and Anthony Santago. I have enjoyed working with each of you, as well as getting to know you outside iii of the lab. In fact, some of my fondest memories were from times when we were not in the lab! You have each provided support in more ways than you probably realize and I am thankful for each of you. Without your hard work, I would probably still be recruiting and testing participants. Not only have you been irreplaceable for data collection and study preparation, but in academic conversations, journal clubs, and the dozens of my practice talks you have sat through. Although, I think it is safe to say that my biggest regret is that we never followed through on our intentions to run a zombie biomechanics study. It would have been spectacular! My former officemate, Jennifer Jordan. You get your own paragraph, my dear, because you just can’t be combined with anything else. It is an understatement to say I genuinely enjoyed sharing an office with you for two years. We really were like “peas and carrots” and my organizational skills grew by leaps and bounds during our tenure in the back hall office of MRI. I am going to miss catching up with life, work, and quilting progress over coffee. Although, maybe we should skip the coffee and plan a second visit to Argentina! But, most importantly, thank you for being such a true and genuine friend. Life outside the classroom is sometimes, if not always, more important. Friends and student groups have played such an integral role in my ability to relax (yes, I did do that every now and again!). First Presbyterian Church, you have provided me with spiritual rejuvenation to sustain me and challenges that have helped me to grow. Graduate Christian Fellowship has played such an integral role in maintaining my emotional and spiritual balance. Rob and Rebecca Alexander, thank you for your special love of graduate students – and of course the delicious homemade meals you make for us every Wednesday! You have given me an example that I hope to follow and pay-forward to iv other graduate students one day. Megan Johnston, Meredith Greene, and Katherine Williford, you are dear friends that I have loved spending time with. Our sidewalk conversations and breakfast dates have been wonderful and I will miss them terribly! Megan, of course we were destined to be “birds of a feather” once we realized that both our first and middle names are off by just one letter. I am so glad that we have become such close friends throughout grad school, and being known to all of GCF as “H” and “H-less” has just been fun. Last, but certainly not least, my family. You have been my unwavering support system and there truly are no words to express just how thankful I am to each of you. Mom and Dad, you have laughed and cried right alongside of me. You have talked to me on the phone for countless hours and driven through the never-ending mountains of West Virginia to come and visit me. There should be an award of some type for parents of graduate students, because you have certainly earned one for your supportive role in this adventure of mine! Grandma and Grandpap, you have shown me nothing but love and encouragement. You have been faithful prayer warriors on my behalf, and I am grateful for our weekly phone calls, which helped keep me grounded and from taking things too seriously. Outside of my advisor and committee, Grandma is probably one of only a few other people who would have read this dissertation from cover to cover. While she isn’t here for the last part of this journey and won’t get to read this, I know she is rejoicing over this accomplishment. Stacey, you are my sister, my confidant, and my dearest friend. You have shared in so much of this journey with me and I am grateful for your company along the way. You have understood the highs and lows in ways that most folks can’t, and you’ve always been supportive. Max, you are such a loving and faithful (and v very fuzzy!) companion. You’ve taught me that there is always time for a snuggle and a purr; I’m not sure who “rescued” whom. To all my family, thank you for your love and support. This work would not have been possible without the generous support of my funding sources. Resources for the various parts of research contained in this dissertation were provided by: The Ruth L. Kirschstein National Research Service Award (NRSA) from the National Institute on Aging of the National Institutes of Health (#F31AG040921), Wake Forest University Claude D. Pepper Older Americans Center, National Institute on Aging (#P30AG021332), National Science Foundation (#1405246), Wake Forest School of Medicine Center for Biomolecular Imaging, Wake Forest University Cross-Campus Collaboration, Wake Forest University Science Research Fund. vi TABLE OF CONTENTS TABLE OF CONTENTS .................................................................................................. vii TABLE OF FIGURES ....................................................................................................... xi TABLE OF TABLES ...................................................................................................... xiii LIST OF ABBREVIATIONS .......................................................................................... xvi ABSTRACT .................................................................................................................... xvii 1. INTRODUCTION ........................................................................................................ 1 1.1 Muscle Anatomy and Physiology ........................................................................ 4 1.2 Aging .................................................................................................................