Neuromuscular Coordination during Slope Walking Andrea N. Lay

253 Pages·2005·2.29 MB·English

Neuromuscular Coordination during Slope Walking

A Thesis
Presented to
The Academic Faculty

by

Andrea N. Lay

In Partial Fulfillment
Of the Requirements for the Degree
Doctor of Philosophy in Bioengineering

School of Mechanical Engineering
Georgia Institute of Technology
December 2005
Neuromuscular Coordination during Slope Walking

Approved by:

Dr. Robert J. Gregor, Advisor Dr. T. Richard Nichols, Advisor
School of Applied Physiology Department of Physiology
Georgia Institute of Technology Emory University School of Medicine
Department of Rehabilitation Medicine Department of Biomedical Engineering
Department of Physiology Emory University and Georgia Tech
Emory University School of Medicine

Dr. Thomas J. Burkholder Dr. Richard L. Segal
School of Applied Physiology Department of Allied Health Sciences
Georgia Institute of Technology Division of Physical Therapy
University of North Carolina

Dr. Lena H. Ting Dr. Imme Ebert-Uphoff
Department of Biomedical Engineering School of Mechanical Engineering
Emory University and Georgia Tech Georgia Institute of Technology

Approved: October 19, 2005
ACKNOWLEDGMENTS

I am deeply grateful to the many people who, throughout the course of my life,
have helped to shape my personality, guide my education, and forge new pathways for
my future. Although I cannot possibly mention all of them individually, I realize it is
because of my interaction with each of them that I am writing this thesis today.
I would first like to thank my master’s thesis advisors, Drs. Glen Livesay and Kay
C Dee, for their incredible enthusiasm as teachers and mentors, for encouraging my
interest in biomedical research, and for pushing me to apply to graduate school. I truly
appreciate their guidance and friendship.
There are numerous people here at Georgia Tech who deserve thanks for helping
me through my dissertation work. I would like to thank the students who have helped me
with this project over the last three years: Chris Herman, Sam Hale, and Daniel Lai.
Their enthusiasm and inquisitiveness helped motivate me, and their hard work was
invaluable in finishing this project. I would also like to acknowledge my colleagues from
the School of Applied Physiology, Drs. Boris Prilutsky, Guay-Haur Shue, Young-Hui
Chang, and Huub Mass, as well as Webb Smith, who have so generously helped me with
everything from designing experiments, to modifying programs, to reading manuscripts
and thesis chapters, to generating ideas when I was stuck. I have truly enjoyed working
with them. I sincerely appreciate the support and guidance of Drs. Lena Ting and Tom
Burkholder, whose ideas and suggestions challenged me to think beyond the obvious
answers in developing this project. I would like to thank Drs. Rick Segal and Imme
Ebert-Uphoff for their encouragement and guidance as members of my thesis committee.
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I owe a very special ‘Thank you’ to Dr. Richard Nichols for his role as my co-advisor. In
spite of his incredibly busy schedule, he has provided valuable feedback, suggestions,
and advice at every step during this process. He is a wonderful person and an incredible
scientist, and I am grateful that he has been involved in my project. Dr. Chris Hass has
been an unofficial mentor to me throughout my time here at Georgia Tech, and for that he
deserves my most heartfelt thanks. Without his teaching, support, positive attitude, and
encouragement, which continued even after he left Georgia Tech, this project would not
have been successful. More than that, though, his friendship made my time here a lot
more enjoyable. I expect that he will be a great advisor to many students in the future.
And last, but not least, I would like to thank Dr. Robert Gregor. He accepted me as a
student when it seemed like I was out of options and he helped me learn a whole new
field of study; through it all he has been an incredible mentor. I deeply appreciate that he
was interested in my life, and not just my work, and I consider myself incredibly lucky to
have “ended up” here at Georgia Tech in Bob’s lab.
My time at Georgia Tech has included a lot more than just earning a degree. The
friends I have made here in Atlanta are an outstanding group of people; without them my
experience here would have been unquestionably less enjoyable. Thank you Adam,
Allison, Anne Claire, Chris L., Chris W., Diane, Geke, Gretchen, Huub, Jeff, Jesse, John
C., John W., Mary, Meghan, Nimisha, Sarah, and Stacey!
It almost goes without saying that I am incredibly grateful to my entire family for
their unfailing love, support, confidence and encouragement. I would especially like to
thank my parents for everything they have done for me over the years. I thank them for
pushing me to excel, for teaching me to love learning, for encouraging me to be a better
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person, and for always being there to help me sort through my problems. My brother and
sister also deserve special recognition. Although we did not always get along as kids I
have really enjoyed becoming friends with them as we have gotten older. I thank them
both for their love and friendship. Finally, I am indebted to Brian for his constant love
and support. Whether halfway around the world or here in Atlanta, he was there to listen
to me and encourage me. I am truly blessed to have him in my life.
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TABLE OF CONTENTS

ACKNOWLEDGMENTS.................................................................................................i
LIST OF TABLES..........................................................................................................vii
LIST OF FIGURES.........................................................................................................ix
LIST OF ABBREVIATIONS.......................................................................................xiii
SUMMARY.....................................................................................................................xv
CHAPTER 1: INTRODUCTION...................................................................................1
Aims........................................................................................................................8
Significance...........................................................................................................13
Limitations............................................................................................................14
CHAPTER 2: BACKGROUND...................................................................................17
Historical Perspective...........................................................................................17
CPGs in Humans...................................................................................................19
Biomechanics and Neural Control........................................................................20
Perturbations and Control Strategies....................................................................28
Slope Walking in Quadrupeds..............................................................................30
Slope Walking in Humans....................................................................................34
Backward Locomotor Tasks in Humans...............................................................39
CHAPTER 3: THE INSTRUMENTED RAMPED WALKWAY.............................41
Introduction...........................................................................................................41
The System............................................................................................................42
Experimental Analyses.........................................................................................45
Natural Frequency...........................................................................................45
Center of Pressure...........................................................................................46
Force...............................................................................................................47
Ground Reaction Forces.................................................................................48
Marker Tracking.............................................................................................49
Results...................................................................................................................49
Natural Frequency...........................................................................................49
Center of Pressure...........................................................................................50
Force...............................................................................................................50
Ground Reaction Forces.................................................................................52
Marker Tracking.............................................................................................53
Discussion.............................................................................................................57
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CHAPTER 4: METHODS............................................................................................59
Participant Preparation..........................................................................................59
Experimental Protocol..........................................................................................60
Data Processing.....................................................................................................62
Gait Cycle Parameters...........................................................................................68
CHAPTER 5: FORWARD DOWNSLOPE WALKING...........................................71
Introduction...........................................................................................................71
Results...................................................................................................................72
Joint Kinematics..............................................................................................72
Ground Reaction Forces.................................................................................74
Joint Kinetics..................................................................................................78
Joint Power......................................................................................................81
Muscle Activity...............................................................................................83
Correlations between Muscle Activity and Kinetics......................................88
Discussion.............................................................................................................91
Joint Kinematics..............................................................................................91
Ground Reaction Forces.................................................................................91
Joint Kinetics..................................................................................................92
Joint Power......................................................................................................92
Knee Joint Biomechanics................................................................................93
Muscle Activity...............................................................................................95
Joint Kinetics and Muscle Activity at the Hip and Knee................................96
Joint Kinetics and Muscle Activity at the Knee and Ankle............................98
Conclusions...........................................................................................................99
CHAPTER 6: FORWARD UPSLOPE WALKING.................................................101
Introduction.........................................................................................................101
Results.................................................................................................................102
Joint Kinematics............................................................................................102
Ground Reaction Forces...............................................................................105
Joint Kinetics................................................................................................108
Joint Power....................................................................................................111
Muscle Activity.............................................................................................113
Correlations between Kinetics and EMG.....................................................118
Discussion...........................................................................................................122
Joint Kinematics............................................................................................122
Ground Reaction Forces...............................................................................122
Joint Kinetics................................................................................................123
Joint Power....................................................................................................123
Hip Joint Biomechanics................................................................................124
Muscle Activity.............................................................................................126
Joint Kinetics and Muscle Activity at the Hip and Knee..............................126
Joint Kinetics and Muscle Activity at the Ankle and Knee..........................128
Conclusions.........................................................................................................131
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CHAPTER 7: BACKWARD SLOPE WALKING...................................................136
Introduction.................................................................................................................136
Part I: A Brief Comparison to Forward Walking...............................................139
Part II: Backward Upslope Walking..................................................................147
Joint Kinematics and GRF............................................................................147
Joint Kinetics................................................................................................147
Joint Power....................................................................................................151
Muscle Activity.............................................................................................153
Correlations between Kinetics and Muscle Activity....................................158
Discussion.....................................................................................................163
Comparison to Forward Slope Walking.......................................................165
Part III: Backward Downslope Walking............................................................168
Joint Kinematics and GRF............................................................................168
Joint Kinetics................................................................................................168
Joint Power....................................................................................................172
Muscle Activity.............................................................................................174
Correlations between Kinetics and Muscle Activity....................................178
Discussion.....................................................................................................182
Comparison to Forward Slope Walking.......................................................184
Conclusions.........................................................................................................186
CHAPTER 8: GENERAL SUMMARY AND FUTURE WORK...........................190

APPENDIX A
FORWARD WALKING ENSEMBLE AVERAGE EMG SIGNALS.....................198

APPENDIX B
ADDITIONAL BACKWARD UPSLOPE WALKING DATA................................205
Joint Kinematics..................................................................................................205
Ground Reaction Forces.....................................................................................209
Muscle Activity...................................................................................................211
APPENDIX C
ADDITIONAL BACKWARD DOWNSLOPE WALKING DATA.........................216
Joint Kinematics..................................................................................................216
Ground Reaction Forces.....................................................................................218
Muscle Activity...................................................................................................221

WORKS CITED............................................................................................................226

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LIST OF TABLES

Table 1. Average (SD) Position of the Calculated COP (in m).......................................51
Table 2. Average (SD) (in N) and Coefficient of Variability (%) of Force Output........52
Table 3. Repeatability of Ground Reaction Force Data...................................................53
Table 4. Average (SD) Stance Times (s).........................................................................56
Table 5. Difference in Average Marker Position between Conditions A and B (in m)...56
Table 6. Participant Information......................................................................................59
Table 7. Number of Forward Walking Trials Used in Processing...................................63
Table 8. Number of Backward Walking Trials Used in Processing................................63
Table 9. Forward Walking Points of Interest used for Statistical Analysis.....................65
Table 10. Backward Walking Points of Interest used for Statistical Analysis................66
Table 11. Forward Walking Gait Cycle Parameters........................................................69
Table 12. Backward Walking Gait Cycle Parameters.....................................................70
Table 13. Downslope Walking Joint Angle POI Data.....................................................74
Table 14. Downslope Walking GRF Component POI Data............................................77
Table 15. Downslope Walking Joint Moment POI Data.................................................80
Table 16. Average Percent of Stance Phase when Power is Absorbed...........................81
Table 17. Upslope Walking Joint Angle POI Data........................................................104
Table 18. Upslope Walking GRF Component POI Data...............................................107
Table 19. Upslope Walking Joint Moment POI Data....................................................110
Table 20. Average Percent of Stance Phase when Power is Generated.........................113
Table 21. Backward Upslope Walking Joint Moment POI Data...................................150
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Table 22. Power Generation during Backward Upslope Walking Stance.....................151
Table 23. Backward Downslope Walking Joint Moment POI Data..............................171
Table 24. Power Generation during Backward Downslope Walking Stance................172
Table 25. Backward Upslope Walking Joint Angle POI Data.......................................207
Table 26. Backward Upslope Walking GRF Component POI Data..............................209
Table 27. Backward Downslope Walking Joint Angle POI Data..................................218
Table 28. Backward Downslope Walking GRF Component POI Data.........................219

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