Mechanics, Modelling and Musculoskeletal Injuries
Andris Freivalds,
CRC Press, 2004
ISBN 0-7484-0926-2
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Biomechanics of the Upper Limbs Mechanics, Modelling and Musculoskeletal Injuries Andris Freivalds, CRC Press, 2004 ISBN 0-7484-0926-2 |
Preface
What is biomechanics and why study it?
Biomechanics is the science that deals with forces and their effects, applied to biological systems. For this book, though, the focus will be exclusively on the upper limbs of the human. Over the last twenty years or so, there has been a tremendous increase in the number of work-related musculoskeletal disorders (WRMSDs) in the upper limbs. Not only do these preventable injuries produce unnecessary pain, suffering, and expense in workers, they also place an undue financial burden on industry in our tight economy. By better understanding the forces and their effects on the human body, the ergonomist may have a better insight into the role of various job stressors on the development of these disorders. With better control of these job stressors and the work place environment, the current epidemic of WRMSDs may perhaps be brought under control. In thus so doing, both the workers and companies will benefit. Although, much effort has already been expended by NIOSH and the medical community in understanding WRMSDs and educating the practitioners, further work is still needed, and this book may help in the process.
Why this book was written?
The objectives of this book are to provide a practical up-to-date engineering-oriented graduate level textbook on the biomechanics of the upper limbs. There are numerous other books providing general introductions to cumulative trauma disorders and medical management to the lay person and several serious texts on the biomechanics of manual material handling and low back problems. However, none focuses solely on the upper limbs, where most of the work-related musculoskeletal disorders seem to reside. Furthermore, this textbook emphasizes the musculoskeletal components involved, engineering models of these components, and measurement and prediction of injury potential based on these models.
For whom was this book written?
This book was primarily intended as a university textbook for graduate-level engineering or kinesiology students, the future practitioners in the WRMSD research area. A large amount of material was collected from various research literature sources and technical reports from very diverse disciplines. It is hoped that this material was distilled into a happy medium of medical and engineering expertise, at a technical level that is appropriate for the reader. The book may also prove useful to researchers, industrial ergonomists, industrial hygienists, and medical professionals as a reference text to supplement their professional material.
How is the book organized?
The book is organized into ten chapters. The first three chapters provide an introduction to the human musculoskeletal system, neuromuscular physiology and the motor control system. Chapters 4 and 5 present the mechanics and models of the various components of the neuromuscular systems as well as models of larger systems. Chapter 6 discusses the various WRMSDs and their associated risk factors. The Chapters 7 and 8 present the types instruments and analyses tools than can be used to identify the WRMSDs in the industrial workplace. The last two chapters provide specific applications to hand tools and computer workstations, with which most of the upper limb WRMSDs have been associated. Thus, one chapter can be roughly covered every one and a half weeks in a typical semester-long course.
This textbook also attempts to assist the educator by providing numerous examples and problems with each chapter. A web site (http://www.ie.psu.edu/courses/ie552/index.htm) is available for on-line notes, background material, solutions, and sample exams. Comments and suggestions for improvement by users of this textbook are greatly appreciated. This is especially important if any outright errors are detected. Please simply respond to the OOPS! button on the web site or contact the author directly by e-mail: axf@psu.edu. As with any web site, this one will also continually evolve.
Acknowledgments
The author wishes to acknowledge Professor Don B. Chaffin for providing him with the training and tools, as well as a model, to proceed with this endeavor. He thanks his graduate students, Neil Davidoff, Lynn Donges, Gerald Fellows, Carol Heffernan, Hyunkook Jang, Dongjoon Kong, Yongku Kong, Kentaro Kotani, Cheol Lee, Brian Lowe, Glenn Miller, Seikwon Park, Vishal Seth, Roberta Weston, Heecheon You, and Myunghwan Yun, for working long hours in collecting the research data on which much of this book was based. Last, but not least, he expresses sincere gratitude to his wife, Dace Freivalds, for her patience, support, and valued assistance on the production of this textbook.
CONTENTS
Preface
Chapter 1 INTRODUCTION TO BIOMECHANICS
1.1 What is Biomechanics?
1.2 Basic Concepts
1.3 Coordinate Systems
1.4 Force Vector Algebra
1.5 Static Equilibrium
1.6 Anthropometry and Center of Mass Determination
1.7 Friction
1.8 Dynamics
Questions
Problems
References
Chapter 2 STRUCTURE OF THE MUSCULOSKELETAL SYSTEM
2.1 Gross Overview of Movements
2.2 The Skeletal System
2.3 Mechanical Properties of Bone
2.4 Soft Connective Tissue
2.5 Joints
2.5.1 Articular joints
2.5.2 Joint lubrication
2.5.3 Wear and osteoarthritis
2.5.4 Cartilaginous joints
Questions
Problems
References
Chapter 3 NEUROMUSCULAR PHYSIOLOGY AND MOTOR CONTROL
3.1 Introduction to Musculature
3.2 Structure of Muscle
3.3 Basic Cell Physiology
3.4 The Nervous System
3.5 The Excitation-Contraction Sequence
3.6 Motor Units
3.6.1 Types of motor units
3.6.2 Motor unit twitch
3.7 Basic Muscle Properties (Mechanics)
3.7.1 Active length-tension relationship
3.7.2 Passive length-tension relationship
3.7.3 Velocity-tension relationship
3.7.4 Active state properties
3.7.5 Developments leading to Hill’s muscle model
3.7.6 Fatigue and Endurance
3.8 Energy, Metabolism and Heat Production
3.9 Receptors
3.9.1 Muscle spindles
3.9.2 Golgi Tendon Organs
3.9.3 Other Receptors
3.10 Reflexes and Motor Control
3.10.1 Stretch reflex
3.10.2 γ-loop control
3.10.3 α-γ coactivation
3.10.4 Reciprocal inhibition
3.10.5 Clasp-knife reflex
3.10.6 Other polysynaptic reflexes
Questions
Problems
References
Chapter 4 MODELING OF MUSCLE MECHANICS
4.1 Laplace Transforms and Transfer Functions
4.1.1 Partial fraction expansion
4.1.2 Transfer functions
4.2 Viscoelastic Theory
4.3 Hill’s Muscle Models
4.3.1 Active muscle response
4.3.2 Force buildup
4.3.3 Stress relaxation
4.3.4 Creep
4.3.5 Time constant
4.4 Frequency Analysis
4.4.1 Generalized approach
4.4.2 Magnitude and phase angle in the frequency domain
4.4.3 Magnitude and phase angle in the Laplace domain
4.5 Frequency Analysis of Passive Muscle
4.6 Hatze’s Multi-element Model
4.7 Applications of the Hatze Muscle Model
4.8 Control Theory and Motor Control
4.8.1 Basic concepts
4.8.2 First-order system
4.8.3 Second-order system
4.8.4 Human information processing and control of movements
4.9 Root Locus Approach to Muscle Modeling
4.9.1 The root locus method
4.9.2 Muscle spindle model
4.9.3 Time delays
4.9.4 Velocity control
4.9.5 Reflex stiffness
Questions
Problems
References
Chapter 5 MODELS OF THE UPPER LIMBS
5.1 Anatomy of the Hand and Wrist
5.1.1 Bones of the hand and wrist
5.1.2 Joints of the hand
5.1.3 Muscle of the forearm, wrist, and hand
5.1.4 The flexor digitorum profundus and flexor digitorum superficialis
5.1.5 Flexor tendon sheath pulley systems
5.1.6 Wrist mechanics
5.1.7 Select finger anthropometry data
5.2 Static Tendon Pulley Models
5.3 Dynamic Tendon-Pulley Models
5.4 Complex Tendon Models
5.4.1 Reduction methods
5.4.2 Optimization methods
5.4.3. Combined approaches
5.5 A Two-Dimensional Hand Model
5.6 Direct Measurement Validation Studies
5.7 Critical Evaluation of Modeling Approaches
Questions
Problems
References
Chapter 6 MUSCULOSKELETAL DISORDERS AND RISK FACTORS
6.1 The Extent of the Problem
6. 2 Common Musculoskeletal Disorders and Their Etiology
6.2.1 Tendon disorders
6.2.2 Muscle disorders
6.2.3 Nerve disorders
6.2.4 Vascular disorders
6.2.5 Bursa disorders
6.2.6 Bone and cartilage disorders
6.3 Medical Diagnosis and Treatment of MSDs
6.4 Epidemiologic Approach to MSDs
6.4.1 Introduction to epidemiology
6.4.2 Statistical analyses
6.4.3 Multivariate modeling
6.4.4 Quality of epidemiological research
6.5 The Scientific Research and Evidence for Occupational Risk Factors
6.5.1 Neck disorders
6.5.2 Shoulder disorders
6.5.3 Elbow disorders
6.5.4 Hand/Wrist - Carpal Tunnel Syndrome
6.5.5 Hand/Wrist - Tendinitis
6.5.6 Hand/Arm - Vibration Syndrome
6.6 The Scientific Research and Evidence for Psychosocial Risk Factors
6.7 Iatrogenesis - A Contrarian View
Questions
Problems
References
Chapter 7 INSTRUMENTATION
7.1 Introduction
7.2 Wrist and Finger Motion Measurement
7.2.1. Types of measurement devices
7.2.2. Calibration methods
7.2.3 Static measurements - range of motion
7.2.4 Dynamic measurements - angular velocity and acceleration
7.3 Pressure and Force Distribution Measurements
7.3.1 Early pressure devices
7.3.2 Force sensing electronic components
7.3.3 Integrated touch glove system
7.4 Nerve Conduction Measurements
7.4.1 Basic concepts
7.4.2 Nerve stimulation and recording
7.4.3 Response measures
7.4.4 Limitations
7.5 Electromyography
7.5.1 EMG instrumentation
7.5.2 EMG analysis
Questions
Problems
References
Chapter 8 JOB AND WORKSITE ANALYSIS
8.1 The Need for Job Analysis
8.2 Reliability and Validity of Assessment Tools
8.2.1 Basic concepts
8.2.2 Reliability of assessments
8.2.3 Reliability of analysts
8.2.4 Accuracy and precision
8.2.5 Applications
8.3 Initial Identification of Musculoskeletal Injury Problems
8.4 Gross Posture and Task Analyses
8.5 Quantitative Upper Limb WRMSD Risk Assessment Tools
8.6 Data Driven Upper Limb WRMSD Risk Index
Questions
Problems
References
Chapter 9 HAND TOOLS
9.1 Introduction
9.1.1 Historical development of tools
9.1.2 Tools and musculoskeletal injuries
9.1.3 General tool principles
9.2 General Biomechanical Considerations of Tools
9.2.1 Anatomy and types of grip
9.2.2 The biomechanics of a power grip
9.2.3 The biomechanics of a precision grip
9.2.4 Measurement of skin coefficient of friction
9.2.5 Grip force coordination
9.2.6 Static muscle loading
9.2.7 Awkward wrist position
9.2.8 Tissue compression
9.2.9 Repetitive finger action
9.3 Handles for Single-Handled Tools
9.3.1 Handle length
9.3.2 Handle diameter
9.3.3 Handle shape
9.3.4 Texture and materials
9.3.5 Angulation of handle
9.4 Handles for Two-Handled Tools
9.4.1 Grip span
9.4.2 Gender
9.4.3 Handedness
9.5 Other Tool Considerations
9.5.1 Posture
9.5.2 Weight
9.5.3 Gloves
9.5.4 Vibration
9.5.5 Rhythm
9.5.6 Miscellaneous
9.6 Agricultural and Forestry Tools
9.6.1 Shovels and spades
9.6.2 Axes and hammers
9.6.3 Saws
9.6.4 Other agricultural tools
9.7 Industrial Tools
9.7.1 Pliers
9.7.2 Screwdrivers
9.7.3 Knives
9.7.4 Meat hooks
9.7.5 Power tools
9.7.6 Railroad tools
9.7.7 Mining tools
9.7.8 Miscellaneous tools
Questions
Problems
References
Chapter 10 THE OFFICE ENVIRONMENT
10.1 General Musculoskeletal Problems
10.2 The Seated Workplace
10.2.1 The seated posture
10.2.2 Seated posture at a computer workstation
10.2.3 Determination of seated comfort
10.2.4 Seat pressure
10.2.5 Sit-stand, forward-sloping, and saddle chairs
10.2.6 The work surface and line of sight
10.3 The Keyboard
10.3.1 Standard keyboard features
10.3.2 Split and sloped keyboards
10.3.3 Layout of keys
10.3.4 Chord keyboards
10.3.5 Numeric keypads
10.4 The Mouse and Other Cursor-positioning Devices
10.4.1 Cursor positioning
10.4.2 The mouse
10.4.3 Mouse alternatives
10.5 Notebooks and Hand-Held PCs
10.6 Control Measures
10.6.1 Rest pauses
10.6.2 Exercises
Questions
Problems
References
Glossary
Author Index
Subject Index