Physiology of Exercise in Spinal Cord Injury (eBook)

Dr. Taylor is an integrative physiologist with a research focus on the human cardiovascular system and the effects of aging, exercise, and pathophysiology. He has conducted clinical/translational research on cardiovascular autonomic control at Harvard Medical School for over twenty years. His work has ranged across various pathophysiologic conditions, including chronic fatigue syndrome, disorders of sleep, and traumatic brain injury. A current primary area of research is exercise for those with spinal cord injuries to prevent inactivity-related cardiovascular deficits.

Contents 6
Chapter 1: The Physiology of Exercise in Spinal Cord Injury (SCI): An Overview of the Limitations and Adaptations 8
1.1 Motor Limitations and Potential Adaptations 9
1.2 Cardiovascular Implications 10
1.3 Ventilatory Limitations 11
1.4 Thermoregulatory Considerations 11
1.5 Alterations in Body Composition and Inflammation 12
1.6 Impact on Bone Fracture Risk 12
1.7 Pain 13
1.8 Conclusion 13
References 14
Chapter 2: Physiology of Motor Deficits and the Potential of Motor Recovery After a Spinal Cord Injury 19
2.1 Introduction 19
2.2 Adaptation of Neuromuscular Properties After a SCI 22
2.3 Animal Studies 22
2.3.1 Adaptations Post-injury 22
2.3.2 Rehabilitation Strategies 23
2.4 Human Studies 24
2.4.1 Adaptations Post-injury 24
2.4.2 Rehabilitative Strategies 25
2.5 Bases for Automaticity in the Control of Movement 26
2.6 Sensory Input to the Spinal Cord Defines the Dynamics of the Physiological States in Controlling Movement After a SCI 27
2.7 Fundamental Elements of Controlling Movement After a SCI 28
2.8 SCI and Motor Unit Properties and Recruitment Order 29
2.8.1 Frequency of Motor Unit Firing 30
2.8.2 Amplitude of Motor Unit Potentials 30
2.9 Spinal Learning of a Motor Skill After a SCI 31
2.10 Assist-as-Needed Experiments Reflect Inherent Stochastic Variation in Spinal Networks 31
2.11 Conceptualizing Neuromodulation as a Network Phenomenon 34
References 36
Chapter 3: Role of Activity in Defining Metabolic and Contractile Adaptations After SCI 42
3.1 Metabolic and Contractile Alterations After SCI 43
3.1.1 Muscle Atrophy 44
3.1.2 Myotypology 45
3.1.3 Muscle Metabolism 45
3.1.4 Muscle Contractile Properties 46
3.1.5 Vascularization 47
3.2 Effects of Activity on Muscle Adaptations After SCI 48
3.2.1 Electrical Stimulation (ES) 49
3.2.2 Effects on Muscle Atrophy 49
3.2.3 Effects on Myotypology 50
3.2.4 Effects on Metabolism 51
3.2.5 Effects on Contractile Properties 52
3.2.6 Effects on Vascularization 52
References 53
Chapter 4: Respiratory System Responses to Exercise in Spinal Cord Injury 56
4.1 Respiratory Function at Rest 57
4.2 Breathing Patterns During Exercise 60
4.3 Control of Exercise Hyperpnea 63
4.4 Respiratory Limitations 64
4.5 Cardiopulmonary Interactions 66
4.6 Methods to Augment Respiratory Function 68
4.6.1 Exercise Training 68
4.6.2 Respiratory Muscle Training 69
4.6.3 Abdominal Binding 71
4.7 Concluding Remarks and Future Directions 74
References 74
Chapter 5: Alterations in Cardiac Electrophysiology After Spinal Cord Injury and Implications for Exercise 81
5.1 Introduction 82
5.2 Mid-Thoracic SCI 83
5.3 Myocardial Damage Following SCI 84
5.4 Altered Autonomic Control of the Heart and Vasculature Following SCI 85
5.5 Altered Cardiac Electrophysiology Following SCI 87
5.6 Autonomic Neuroplasticity Following SCI 89
5.6.1 Incidence of Cardiac Arrhythmias Among Individuals with SCI 90
5.7 Susceptibility to Ventricular Arrhythmias Following SCI 92
5.8 Implications for Exercise Following SCI 93
5.9 Exercise and the Importance of Venous Return 95
5.10 Exercise and Autonomic Dysreflexia 96
5.11 Summary and Integration 98
References 99
Chapter 6: Cardiovascular Responses to Exercise in Spinal Cord Injury 108
6.1 Impact of a Spinal Cord Injury on the Cardiovascular System 109
6.1.1 Cardiac Function and Structure 109
6.1.2 Vascular Structure 111
6.1.3 Vascular Function 113
6.1.4 Time-Course of Adaptation 116
6.2 Exercise and Cardiac Responses 117
6.3 Exercise and Exercise-Induced Blood Flow 119
6.3.1 Active Areas 119
6.3.2 Non-active, Paralyzed Areas 119
6.3.3 Blood Redistribution 120
6.4 Adaptations to Exercise Training 121
6.5 Summary 123
References 123
Chapter 7: Thermoregulatory Considerations for the Performance of Exercise in SCI 130
7.1 Introduction 130
7.2 Anatomy and Physiology of Normal Thermoregulation 132
7.3 Evidence for Impaired Thermoregulation Following SCI 135
7.3.1 Importance of Level of SCI 135
7.3.2 Evidence of Thermoregulatory Impairment 136
7.4 Autonomic Mechanisms Underlying Thermoregulatory Impairment 139
7.4.1 Set-Point Theory 139
7.4.2 Reduced Afferent Input 139
7.4.3 Reduced Efferent Output and Target Sensitivity 141
7.4.3.1 Insensate Skin 141
7.4.3.2 Sensate Skin 143
7.4.4 Cardiovascular Impairments that Affect Thermoregulation 144
7.4.5 Medications 145
7.4.6 Compensatory Mechanisms 146
7.5 Considerations Based on Exercise Modalities 146
7.5.1 Upper vs. Lower Body Exercise 147
7.5.2 Training Status 148
7.6 Strategies for Mitigating Thermoregulatory Dysfunction 149
7.6.1 Cooling 150
7.6.1.1 Microclimate Cooling Vests 150
7.6.1.2 Refrigerated Headpieces 151
7.6.1.3 Hand/Foot Cooling 151
7.6.1.4 Pre-cooling 152
7.6.2 Artificial Sweating/Water Spray 152
7.6.3 Heat Acclimation 153
7.6.4 Body-Weight-Supported Treadmill Training 155
7.6.5 Strategies for Thermoregulation During Exercise in Cool Environments 155
7.7 Conclusions 156
References 156
Chapter 8: Increased Bone Fracture After SCI: Can Exercise Reduce Risk? 164
8.1 Bone Adaptations After Spinal Cord Injury 164
8.2 Risk for Fractures 166
8.3 Bone Imaging After Spinal Cord Injury 166
8.4 Fracture Risk Assessment After Spinal Cord Injury 167
8.5 Pharmaceutical Interventions 168
8.6 Bone Response to Training 169
8.7 Conclusions 172
References 173
Chapter 9: Alterations in Body Composition After SCI and the Mitigating Role of Exercise 178
9.1 Overview 178
9.2 Adipose Tissue Pathophysiology 179
9.3 Obesity Definitions 180
9.4 Body Composition Assessment 181
9.5 Two Compartment Models 182
9.5.1 Hydrodensitometry 182
9.5.2 Air Displacement Plethysmography 187
9.5.3 Hydrometry 188
9.5.4 Bioelectrical Impedance Analyses 189
9.5.5 Anthropometry 191
9.6 Three Compartment Models 192
9.7 Four Compartment Model 194
9.7.1 Exercise on Body Composition After SCI 194
9.8 Conclusion 197
References 197
Chapter 10: Cardiometabolic Syndrome in SCI: The Role of Physical Deconditioning and Evidence-Based Countermeasures 202
10.1 Introduction 203
10.2 Physical Deconditioning in the Origins of Post-SCI Cardiometabolic Disease 205
10.3 Exercise as an Evidence-Based Countermeasure to CMS Risk Components 206
10.4 Volitional Exercise 208
10.4.1 Volitional Exercise and Dyslipidemia After SCI/D 208
10.4.2 Volitional Exercise to Improve Insulin Sensitivity/Glycemic Response 209
10.4.3 Volitional Exercise to Attenuate Central Obesity 210
10.5 Exercise as Part of a Therapeutic Lifestyle Intervention (TLI) Plan for CMS Risk Reduction 210
10.6 Exercise After SCI: Knowledge Limitations 212
10.7 Conclusion 213
References 214
Chapter 11: The Effect of Acute and Chronic Exercise on Inflammatory Markers in SCI 219
11.1 Inflammation and Exercise 220
11.1.1 Inflammation and the Autonomic Nervous System 221
11.1.2 Inflammation and Humoral Factors 223
11.2 Autonomic Function and Inflammation Following SCI 224
11.2.1 Catecholamines 224
11.2.2 Acute Exercise and the Inflammatory Response 225
11.2.3 Inducing an Inflammatory Response Despite Sympathetic Dysfunction 227
11.2.4 Chronic Exercise and the Inflammatory Risk Marker Profile 229
11.3 Conclusion and Outlook 230
References 231
Chapter 12: Role of Exercise in Alleviating Chronic Pain in SCI 234
12.1 Introduction 234
12.2 Definitions of Pain 235
12.3 Definitions of Exercise 235
12.4 Survey Evidence of Exercise as a Pain Intervention 235
12.5 Exercise as a Pain Intervention in General for Pain After SCI 236
12.6 Associated Psychological Factors Related to Exercise and Pain 238
12.7 Exercise as a Pain Intervention for Shoulder Pain After SCI 239
12.8 Exercise May be Under-utilized by Many Persons with SCI 239
12.9 Conclusion 239
References 240
Chapter 13: Autonomic Alterations After SCI: Implications for Exercise Performance 243
13.1 Introduction 244
13.2 Autonomic Control of the Cardiovascular System 245
13.3 Pathophysiological Mechanisms of Cardiovascular Dysfunction Following SCI 248
13.4 Clinical Consequences of Cardiovascular Control Following SCI 249
13.4.1 Low Resting Blood Pressure 250
13.4.2 Autonomic Dysreflexia 250
13.4.3 Orthostatic Hypotension 253
13.5 Implications of Autonomic Dysfunctions After SCI on Exercise 256
13.5.1 Boosting 258
13.5.2 Ensuing Equality and Safety Using Standardized Autonomic Testing 260
13.6 Summary 261
References 262
Chapter 14: Hybrid Functional Electrical Stimulation Exercise for Improved Cardiorespiratory Fitness in SCI 269
14.1 Introduction 269
14.2 FES of Skeletal Muscles 270
14.2.1 Applications of FES 270
14.2.2 Parameters of FES 271
14.2.3 Muscle Fatigue 271
14.3 Three Types of FES Exercise 272
14.3.1 FES-Cycling Exercise 272
14.3.2 Hybrid FES-Cycling Exercise 273
14.3.3 FES-Rowing Exercise 273
14.4 Aerobic Benefits 273
14.4.1 Acute Response 274
14.4.2 Arms-Only Exercise 274
14.4.3 FES-Cycling Exercise 277
14.4.4 Hybrid FES-Cycling and Hybrid FES-Rowing Exercise 278
14.4.5 Responses to Exercise Training 279
14.4.5.1 Arm-Only Exercise 279
14.4.5.2 FES-Cycling Exercise 279
14.4.5.3 Hybrid FES-Cycling and FES-Rowing Exercise 280
14.5 Discussion 282
References 283