A Comparison of Multipath and Conventional Neuromuscular Electrical Stimulation

Abstract

....................................................................................................................... ii ACKNOWLEDGMENTS ................................................................................................. iv DEDICATION .................................................................................................................... v LIST OF TABLES ............................................................................................................ xv LIST OF ILLUSTRATIONS ........................................................................................... xvi LIST OF ABBREVIATIONS ........................................................................................ xviii CHAPTER I – INTRODUCTION ...................................................................................... 1 Statement of the Problem ................................................................................................ 1 Manuscript 1 Research Questions and Hypotheses ........................................................ 8 Manuscript 1 Research Questions ............................................................................... 8 Manuscript 1 Research Hypotheses ............................................................................ 9 Manuscript 2 Research Questions and Hypotheses ...................................................... 10 Manuscript 2 Research Questions ............................................................................. 10 Manuscript 2 Research Hypotheses .......................................................................... 11 Assumptions .................................................................................................................. 12 Delimitations ................................................................................................................. 12 Limitations .................................................................................................................... 13 Definitions..................................................................................................................... 15 CHAPTER II – REVIEW OF RELATED LITERATURE .............................................. 19 vii Overview ....................................................................................................................... 19 Muscle Fatigue .............................................................................................................. 19 Fatigue Overview ...................................................................................................... 19 NMES-induced Fatigue ............................................................................................ 20 Motor Unit Recruitment ................................................................................................ 22 Voluntary Motor Unit Recruitment .......................................................................... 22 NMES Motor Unit Recruitment................................................................................ 24 Central and Peripheral Pathways .............................................................................. 27 Strategies to Reduce NMES-induced Fatigue............................................................... 31 Overview ................................................................................................................... 31 Frequencies and Pulse Durations .............................................................................. 32 Systematically Altering Frequencies ........................................................................ 37 On:Off Ratio or Duty Cycle ...................................................................................... 41 Stimulus Intensity ..................................................................................................... 43 Variable Frequency Trains ........................................................................................ 44 Accommodation ............................................................................................................ 46 Strategies to Enhance Patient Comfort ......................................................................... 50 Overview ................................................................................................................... 50 Electrode Size ........................................................................................................... 51 Electrode Placement.................................................................................................. 55 viii Current Parameters.................................................................................................... 57 Blunting Strategies .................................................................................................... 63 Additional Comfort Strategies .................................................................................. 65 Patient Characteristics Influencing NMES Tolerance and Comfort Levels ................. 65 Strategies to Maximize NMES-induced Force Production ........................................... 70 Overview ................................................................................................................... 70 Current Parameters.................................................................................................... 71 Variable Frequency Trains ........................................................................................ 75 Electrode Placement.................................................................................................. 76 Joint Position ............................................................................................................. 79 Multipath NMES ........................................................................................................... 80 Visual Analog Scale Validity Evidence ........................................................................ 85 Conclusion .................................................................................................................... 87 CHAPTER III METHODOLOGY ................................................................................. 88 Study Design ................................................................................................................. 88 Design Strengths and Weaknesses ............................................................................ 89 Power Analysis and Sample.......................................................................................... 91 A Priori Power Analysis ........................................................................................... 91 Sample....................................................................................................................... 93 Instrumentation ............................................................................................................. 96 ix Torque Recording ..................................................................................................... 96 Conventional Neuromuscular Electrical Stimulation ............................................... 97 Pencil Electrode ...................................................................................................... 100 Multipath Neuromuscular Electrical Stimulation ................................................... 102 Visual Analog Scale ................................................................................................ 102 Procedures ................................................................................................................... 103 Participant Inclusion and Exclusion Criteria .......................................................... 103 Overview ................................................................................................................. 104 Familiarization Sessions (Days 1-2) ....................................................................... 108 Test Sessions (Days 3-6) ......................................................................................... 110 MVIC Procedures ................................................................................................... 111 NMES and Stimulus Intensity Standardization Procedures .................................... 114 Outcome Measures...................................................................................................... 119 Percent Decline in MVIC Torque ........................................................................... 119 Percent Decline in NMES-induced Torque ............................................................ 120 Percent Decline in Torque-time Integral ................................................................. 120 Total Torque-time Integral ...................................................................................... 122 Self-Reported Discomfort ....................................................................................... 122 Maximum Comfortable Stimulus Intensity ............................................................ 122 Initial Normalized NMES-induced Torque ............................................................ 123 x Statistical Analysis ...................................................................................................... 124 Data Screening ........................................................................................................ 124 Two-way Repeated Measures ANOVA.................................................................. 127 Dependent t-test ...................................................................................................... 128 Effect Sizes ............................................................................................................. 128 CHAPTER IV – STUDY 1 MANUSCRIPT .........................................