The working back : a systems view

A systems approach to understanding and minimizing the causes of low back pain in the workplace

Low back pain affects 80% of the population at some point during their lifetime; it is responsiblefor over 40% of the compensation costs for work-related injuries. This book provides an understanding of the mechanisms influencing low back pain in the workplace and indicates how low back pain might be prevented, saving employers extraordinary amounts in medical costs and protecting workers from the most common on-the-job injury. With a unique, multidisciplinary perspective that shows how various influences or risk factors can be considered collectively, The Working Back: A Systems View:

Explains basic concepts in anatomy and physiology that are essential to understanding and preventing low back pain

Provides a systems perspective on the occupational causes of back pain, not only addressing factors such as spine loading, but also considering the potential impact of psychosocial and organizational interactions, genetics, and physiology

Discusses implementing preventive engineering and administrative controls and integrating risk interventions into the workplace

Offers an expert analysis of current medical research on low back pain in one comprehensive, accessible reference

This book gives readers the knowledge to assess a work environment and prescribe effective interventions. It is a hands-on reference for ergonomists, manufacturing engineers, process engineers, industrial engineers and managers, safety engineers, nurses, therapists, chiropractors, physicians, and workers with back pain. It is also an excellent resource for graduate or undergraduate students of kinesiology, physiology, ergonomics, physical therapy, nursing, industrial design, engineering, and general medicine.

Author Notes

William S. Marras is a Professor in the College of Engineering and the College of Medicine at The Ohio State University and a Fellow of the American Institute of Medical and Biological Engineers, the Human Factors and Ergonomics Society, the International Ergonomics Society, and the Ergonomics Society.

Acknowledgments	p. ix
Chapter 1 Introduction	p. 1
1.1 Audience for the Book	p. 3
1.2 Apolitical Causality Assessment	p. 4
1.3 A Systems View of Low Back Pain Causality	p. 4
1.4 The Reality of Work	p. 5
1.5 How Might the Different Aspects of Work Be Associated with Back Pain	p. 6
1.6 Organization of the Book	p. 8
Chapter 2 Back Pain Magnitude and Potential Risk Factors	p. 11
2.1 What is Back Pain?	p. 11
2.2 How Common is Back Pain?	p. 11
2.3 Back Pain at Work	p. 12
2.4 Epidemiology of Work Risk Factors	p. 13
2.5 Epidemiology of Physical Risk Factors	p. 16
2.6 Epidemiology of Individual (Personal) Risk Factors	p. 18
2.6.1 Age	p. 18
2.6.2 Gender	p. 18
2.6.3 Anthropometry	p. 19
2.6.4 Fitness/Strength	p. 20
2.6.5 Alcohol	p. 20
2.6.6 Smoking	p. 21
2.6.7 Heredity/Genetics	p. 21
2.6.8 Social Class and Psychological Factors	p. 21
2.7 Epidemiology of Work-Related Psychosocial/Organizational Factors	p. 22
2.8 Potential Interaction of Physical and Psychosocial Factors	p. 23
Key Points	p. 25
Chapter 3 Function, Structure, and Support of the Back	p. 29
3.1 Body Coordinates	p. 29
3.2 Bony Structures of the Spine	p. 29
3.3 The Disc (and the Spinal Joint)	p. 31
3.4 Functional Spinal Unit	p. 31
3.5 Spine Support	p. 32
3.6 Ligaments	p. 32
3.7 Muscles	p. 35
3.8 Fascia	p. 35
3.9 Nerves	p. 37
3.10 Blood Vessels	p. 39
3.11 End Plates and Nutrition	p. 40
3.12 Facets	p. 40
3.13 The System	p. 41
Key Points	p. 41
Chapter 4 The Process of Pain	p. 43
4.1 What is Pain?	p. 43
4.2 Origins of Pain	p. 44
4.3 Pain Transmission	p. 44
4.4 The Pain Process	p. 46
4.5 The Inflammatory Process (Cytokines)	p. 48
4.6 Peripheral Nervous System Sensitization	p. 50
4.7 Neuropathic Pain: The Cytokine Cascade and Nerve Sensitization	p. 51
4.8 Pain Mechanisms of the Central Nervous System	p. 51
4.9 Role of the Environment in Central Sensitization	p. 52
4.10 Implications for Low Back Pain	p. 53
4.11 Nerves at Risk of Sensitization	p. 53
4.12 Tissues at Risk of Sensitization	p. 53
4.13 Disk and Nerve Roots	p. 54
4.14 Facet Joints	p. 54
4.15 Muscular-Based Pain	p. 55
4.16 Lumbar Nerve Roots	p. 56
4.17 Relationship between Tissue Loading and Pain	p. 56
4.18 Conclusions	p. 56
Key Points	p. 56
Chapter 5 Potential Pathways to Back Pain	p. 60
5.1 Views of Back Pain Causality	p. 60
5.2 A Unifying Model of Low Back Pain Pathways	p. 63
5.3 The Support Structure Disruption Pathways	p. 65
5.3.1 Support Structure Tolerance	p. 66
5.4 Disc Tolerance Summary	p. 73
5.5 Pain Tolerance	p. 74
5.6 The Muscle Function Disruption Pathway	p. 74
5.7 The Role of Individual Differences in the Pain Pathways	p. 79
5.8 System Feedback	p. 81
5.9 Summary	p. 81
Key Points	p. 82
Chapter 6 The Assessment of Biomechanical Forces Acting on the Low Back	p. 87
6.1 Biomechanical Concepts Applicable to the Back	p. 88
6.1.1 Load Tolerance	p. 88
6.1.2 Moments and Levers	p. 89
6.1.3 External Versus Internal Loading	p. 90
6.2 How can we Modify Internal Spine Loads?	p. 92
6.2.1 Biomechanical Arrangement of the Musculoskeletal Lever System	p. 92
6.2.2 Length-Strength Relationship	p. 92
6.2.3 The Impact of Velocity on Muscle Force	p. 93
6.2.4 Temporal Relationships	p. 94
6.3 Incorporating Spine Load Reductions into the Work System	p. 95
6.4 Loading of the Lumbar Spine	p. 95
6.5 Spine Load Assessments	p. 96
6.6 Models of Spine Load	p. 97
6.7 Biologically Driven Modeling of Spine Loading	p. 100
6.8 Stability-Driven Spine Loading Models	p. 106
6.8.1 Predictions of Muscle (Motor) Control within Torso	p. 108
6.9 What Drives Motor Control? The Mental Model	p. 110
6.10 Summary	p. 112
Key Points	p. 112
Chapter 7 The Influence of Physical Work Factors on Muscle Activities and Spine Loads	p. 117
7.1 Introduction	p. 117
7.2 Industrial Quantitative Surveillance of Physical Exposure	p. 118
7.3 Strength Capacity Assessments of Work Load	p. 119
7.3.1 Static Analyses of Work Load	p. 120
7.4 Dynamic Analyses of Work Load	p. 121
7.5 Surveillance Conclusions	p. 127
7.6 Spine Loading and Task Performance	p. 127
7.7 Spine Loading and Primary Physical Workplace Factors	p. 128
7.7.1 Moment Exposure	p. 128
7.8 Role of Trunk Muscle Cocontraction in Spine Loading	p. 129
7.9 Trunk Motion	p. 130
7.10 Nonsagittal Plane Loading	p. 133
7.10.1 Lateral Motion	p. 134
7.10.2 Twisting Motion	p. 136
7.10.3 Task Asymmetry	p. 138
7.10.4 Lift Height	p. 139
7.10.5 One-Handed Versus Two-Handed Lifting	p. 142
7.11 Lifting Versus Lowering	p. 146
7.11.1 Cumulative Exposure	p. 147
7.12 Duration of Exposure to Lifting Tasks	p. 148
7.13 Worker Experience, Task Frequency, and Moment Exposure	p. 150
7.14 Spine Loading Associated with Modification of Physical Workplace Factors	p. 154
7.14.1 Handles	p. 154
7.15 Lifting While Supporting the Body	p. 156
7.16 Team Lifting	p. 158
7.17 Pushing and Pulling	p. 160
7.18 Seated and Constrained Work Postures	p. 164
7.19 Physical Work Factor Summary	p. 166
7.20 Summary	p. 169
Key Points	p. 170
Chapter 8 Psychosocial and Organizational Factor Influence on Spine Loading	p. 174
8.1 Introduction	p. 174
8.2 Psychosocial and Organizational Interactions	p. 175
8.3 Biomechanical Responses to Psychosocial Environment	p. 176
8.4 Biomechanical Responses to Mental Stress at Work	p. 178
8.5 Expectation	p. 182
8.6 Conclusions	p. 183
Key Points	p. 183
Chapter 9 Individual Factors Role in Spine Loading	p. 187
9.1 Introduction	p. 187
9.2 Gender	p. 187
9.2.1 Personality	p. 193
9.3 Experience	p. 196
9.4 Conclusions	p. 198
Key Points	p. 198
Chapter 10 Physical, Individual, and Psychosocial/Organizational Risk Factor Interactions	p. 200
10.1 When Risk Factors Collide	p. 200
10.2 The Magnitude of Influence of the Three Risk Factor Categories	p. 201
10.3 Can Risk Factor Interactions be Predicted?	p. 206
10.4 Conclusions	p. 207
Key Points	p. 208
Chapter 11 Engineering Controls to Mediate Back Pain at Work: Tools for the Assessment of Physical Factor Impact on Spine Loads and Intervention Effectiveness	p. 210
11.1 Introduction	p. 210
11.2 Static Strength Prediction Programs	p. 211
11.3 Psychophysical Tolerance Limits	p. 212
11.4 Job Demand Index	p. 214
11.5 NIOSH Lifting Guide and Revised Equation	p. 214
11.5.1 The 1981 Lifting Guide	p. 214
11.5.2 The 1993 Revised Equation	p. 216
11.6 Video-Based Biomechanical Models	p. 218
11.7 Lumbar Motion Monitor Risk Assessment	p. 219
11.8 Lifting Threshold Limit Values (TLVs)	p. 222
11.9 Workplace Assessment Comparisons	p. 226
11.10 Conclusions	p. 229
Key Points	p. 229
Chapter 12 Administrative Controls for the Workplace: Psychosocial and Organizational Interventions	p. 232
12.1 Implementing Psychosocial and Organizational Change	p. 232
12.2 Elements of the Process	p. 234
12.3 Traditional Administrative Controls	p. 236
12.3.1 Worker Selection	p. 236
12.3.2 Worker Rotation	p. 236
12.3.3 Training	p. 237
12.3.4 Stretching Programs	p. 237
12.3.5 Back Belts	p. 238
12.4 Summary	p. 239
Key Points	p. 240
Chapter 13 Integrating Risk Interventions into the Workplace	p. 242
13.1 Introduction	p. 242
13.2 Systems Intervention	p. 242
13.3 Examples of Intervention Effectiveness	p. 243
13.3.1 Patient Handling Interventions	p. 243
13.3.2 Types of Physical Interventions	p. 246
13.4 Implementing Both Physical and Psychosocial Interventions	p. 247
13.4.1 Distribution Center Interventions	p. 248
13.5 Summary	p. 248
Key Points	p. 249
Chapter 14 Understanding Recurrent Low Back Pain and Implications for Return to Work	p. 251
14.1 Introduction	p. 251
14.2 The Natural History of Low Back Pain Recovery	p. 252
14.3 How can One Quantify the Extent of Low Back Pain?	p. 253
14.3.1 Impairment Assessment	p. 254
14.3.2 Effort Sincerity	p. 267
14.4 Spine Loading of those Experiencing Low Back Pain	p. 272
14.5 Can Kinematic Impairment Assessments Predict Changes in Spine Loading?	p. 281
14.6 Lifting Exposure Limits for Workers with LBP	p. 285
14.7 Recurrence of LBP and Work	p. 286
14.8 A Return-to-Work Strategy	p. 292
14.9 Conclusions	p. 292
Key Points	p. 293
Chapter 15 Conclusions	p. 298
15.1 Summary	p. 301
Index	p. 303

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