Biomechanics of the upper limbs : mechanics, modeling, and musculoskeletal injuries

1 Introduction to Biomechanics ....................................................... 1 1.1 What Is Biomechanics? .................................................................................1 1.2 Basic Concepts................................................................................................2 1.3 Coordinate Systems.......................................................................................3 1.4 Force Vector Algebra .....................................................................................5 1.5 Static Equilibrium ..........................................................................................8 1.6 Anthropometry and Center of Mass Determination .............................14 1.7 Friction...........................................................................................................20 1.8 Dynamics.......................................................................................................23 Questions................................................................................................................28 Problems.................................................................................................................29 References...............................................................................................................31 2 Structure of the Musculoskeletal System .................................. 33 2.1 Gross Overview of Movements ................................................................33 2.2 The Skeletal System.....................................................................................35 2.3 Mechanical Properties of Bone..................................................................40 2.4 Soft Connective Tissue................................................................................44 2.5 Joints ..............................................................................................................46 2.5.1 Articular Joints.................................................................................46 2.5.2 Joint Lubrication..............................................................................49 2.5.3 Wear and Osteoarthritis .................................................................50 2.5.4 Cartilaginous Joints.........................................................................50 Questions................................................................................................................52 Problems.................................................................................................................52 References...............................................................................................................53 3 Neuromuscular Physiology and Motor Control ........................................................................ 55 3.1 Introduction to Musculature......................................................................55 3.2 Structure of Muscle .....................................................................................57 3.3 Basic Cell Physiology..................................................................................59 3.4 The Nervous System ...................................................................................63 3.5 The Excitation–Contraction Sequence......................................................65 3.6 Motor Units ..................................................................................................68 3.6.1 Types of Motor Units......................................................................68 3.6.2 Motor Unit Twitch ..........................................................................69 3.7 Basic Muscle Properties (Mechanics) .......................................................72 3.7.1 Active Length–Tension Relationship ...........................................72 3.7.2 Passive Length–Tension Relationship..........................................73 3.7.3 Velocity–Tension Relationship ......................................................74 3.7.4 Active State Properties ...................................................................76 3.7.5 Developments Leading to Hill’s Muscle Model ........................76 3.7.6 Fatigue and Endurance ..................................................................78 3.8 Energy, Metabolism, and Heat Production .............................................79 3.9 Receptors.......................................................................................................83 3.9.1 Muscle Spindles...............................................................................84 3.9.2 Golgi Tendon Organs .....................................................................85 3.9.3 Other Receptors...............................................................................87 Questions................................................................................................................96 Problems.................................................................................................................98 References...............................................................................................................98 4 Modeling of Muscle Mechanics ................................................ 101 4.1 Laplace Transforms and Transfer Functions .........................................101 4.1.1 Partial Fraction Expansion...........................................................102 4.1.2 Transfer Functions.........................................................................108 4.2 Viscoelastic Theory ....................................................................................109 4.3 Hill’s Muscle Models ................................................................................ 116 4.3.1 Active Muscle Response .............................................................. 119 4.3.2 Tension Buildup.............................................................................121 4.3.3 Stress Relaxation............................................................................123 4.3.4 Creep ...............................................................................................124 4.3.5 Time Constant................................................................................125 4.4 Frequency Analysis ...................................................................................126 4.4.1 Generalized Approach..................................................................127 4.4.2 Magnitude and Phase Angle in the Frequency Domain........128 4.4.3 Magnitude and Phase Angle in the Laplace Domain.............133 4.5 Frequency Analysis of Passive Muscle ..................................................136 4.6 Hatze’s Multielement Model ...................................................................138 4.7 Applications of the Hatze Muscle Model..............................................149 4.8 Control Theory and Motor Control........................................................150 4.8.1 Basic Concepts ...............................................................................150 4.8.2 First-Order System........................................................................152 4.8.3 Second-Order System ...................................................................153 4.8.4 Human Information Processing and Control of Movements ...160 4.9 Root Locus Approach to Muscle Modeling ..........................................164 4.9.1 The Root Locus Method...............................................................164 4.9.2 Muscle Spindle Model..................................................................176 4.9.3 Time Delays....................................................................................181 4.9.4 Velocity Control .............................................................................184 4.9.5 Reflex Stiffness...............................................................................185 Questions..............................................................................................................189 Problems...............................................................................................................190 References.............................................................................................................191 5 Models of the Upper Limbs ...................................................... 195 5.1 Anatomy of the Hand and Wrist ............................................................195 5.1.1 Bones of the Hand and Wrist......................................................195 5.1.2 Joints of the Hand .........................................................................196 5.1.3 Muscle of the Forearm, Wrist, and Hand .................................197 5.1.4 Flexor Digitorum Profundus and Flexor Digitorum Superficialis ....................................................................................198 5.1.5 Flexor Tendon Sheath Pulley Systems.......................................200 5.1.6 Wrist Mechanics ............................................................................201 5.1.7 Select Finger Anthropometry Data ............................................204 5.2 Static Tendon–Pulley Models ..................................................................206 5.3 Dynamic Tendon–Pulley Models ............................................................210 5.4 Complex Tendon Models .........................................................................212 5.4.1 Reduction Methods.......................................................................212 5.4.2 Optimization Methods .................................................................213 5.4.3 Combined Approaches.................................................................214 5.5 A Two-Dimensional Hand Model...........................................................215 5.6 Direct Measurement Validation Studies ................................................221 5.7 Critical Evaluation of Modeling Approaches .......................................223 Questions..............................................................................................................227 Problems...............................................................................................................228 References.............................................................................................................228 6 Musculoskeletal Disorders and Risk Factors .......................... 233 6.1 The Extent of the Problem .......................................................................233 6.2 Common MSDs and Their Etiology.......................................................234 6.2.1 Tendon Disorders ..........................................................................236 6.2.2 Muscle Disorders...........................................................................237 6.2.3 Nerve Disorders ............................................................................239 6.2.4 Vascular Disorders ........................................................................242 6.2.5 Bursa Disorders .............................................................................242 6.2.6 Bone and Cartilage Disorders .....................................................243 6.3 Medical Diagnosis and Treatment of MSDs .........................................243 6.4 Epidemiologic Approach to MSDs .........................................................250 6.4.1 Introduction to Epidemiology.....................................................250 6.4.2 Statistical analyses.........................................................................258 6.4.3 Multivariate Modeling .................................................................267 6.4.4 Quality of Epidemiological Research.........................................273 6.5 Scientific Research and Evidence for Occupational Risk Factors......275 6.5.1 Neck Disorders ..............................................................................275 6.5.2 Shoulder Disorders .......................................................................280 6.5.3 Elbow Disorders ............................................................................282 6.5.4 Hand/Wrist — Carpal Tunnel Syndrome ................................282 6.5.5 Hand/Wrist — Tendinitis............................................................286 6.5.6 Hand/Arm — Vibration Syndrome...........................................288 6.6 Scientific Research and Evidence for Psychosocial Risk Factors.......288 6.7 Iatrogenesis — A Contrarian View.........................................................291 Questions..............................................................................................................294 Problems...............................................................................................................296 References.............................................................................................................299 7 Instrumentation........................................................................... 311 7.1 Introduction ................................................................................................ 311 7.2 Wrist and Finger Motion Measurement ................................................ 311 7.2.1 Types of Measurement Devices .................................................. 311 7.2.2 Calibration Methods .....................................................................313 7.2.3 Static Measurements — Range of Motion ................................316 7.2.4 Dynamic Measurements — Angular Velocity and Acceleration....................................................................................317 7.3 Pressure and Force Distribution Measurements ..................................320 7.3.1 Early Pressure Devices .................................................................320 7.3.2 Force Sensing Electronic Components.......................................322 7.3.3 Integrated Touch Glove System..................................................327 7.4 Nerve Conduction Measurements..........................................................330 7.4.1 Basic Concepts ...............................................................................330 7.4.2 Nerve Stimulation and Recording..............................................332 7.4.3 Response Measures.......................................................................337 7.4.4 Limitations......................................................................................339 7.5 Electromyography .....................................................................................341 7.5.1 EMG Instrumentation...................................................................343 7.5.2 EMG Analysis ................................................................................344 Questions..............................................................................................................351 Problems...............................................................................................................352 References.............................................................................................................352 8 Job and Worksite Analysis ........................................................ 361 8.1 The Need for Job Analysis .......................................................................361 8.2 Reliability and Validity of Assessment Tools........................................362 8.2.1 Basic Concepts ...............................................................................362 8.2.2 Reliability of Assessments ...........................................................363 8.2.3 Reliability of Analysts ..................................................................365 8.2.4 Accuracy and Precision................................................................370 8.2.5 Applications ...................................................................................373 8.3 Initial Identification of Musculoskeletal Injury Problems ..................376 8.3.1 Initial Steps.....................................................................................376 8.3.2 Surveys and Subjective Ratings..................................................377 8.3.3 Limitations of Surveys .................................................................380 8.4 Gross Posture and Task Analyses ...........................................................380 8.4.1 Early Recording of Postures........................................................380 8.4.2 OWAS..............................................................................................381 8.4.3 Posture Targeting ..........................................................................383 8.4.4 RULA...............................................................................................384 8.4.5 Video Posture Analyses................................................................384 8.4.6 Task Analyses.................................................................................387 8.5 Quantitative Upper Limb WRMSD Risk Assessment Tools ..............389 8.5.1 Checklists........................................................................................389 8.5.2 Strain Index ....................................................................................394 8.5.3 OCRA..............................................................................................394 8.5.4 Recent Developments ...................................................................400 8.6 Data-Driven Upper Limb WRMSD Risk Index....................................400 Questions..............................................................................................................407 Problems...............................................................................................................408 References.............................................................................................................410 9 Hand Tools................................................................................... 417 9.1 Introduction ................................................................................................417 9.1.1 Historical Development of Tools ................................................417 9.1.2 Tools and Musculoskeletal Injuries............................................418 9.1.3 General Tool Principles ................................................................418 9.2 General Biomechanical Considerations of Tools ..................................419 9.2.1 Anatomy and Types of Grip .......................................................419 9.2.2 The Biomechanics of a Power Grip............................................420 9.2.3 The Biomechanics of a Precision Grip.......................................423 9.2.4 Measurement of Skin Coefficient of Friction............................425 9.2.5 Grip Force Coordination ..............................................................426 9.2.6 Static Muscle Loading ..................................................................428 9.2.7 Awkward Wrist Position..............................................................430 9.2.8 Tissue Compression ......................................................................431 9.2.9 Repetitive Finger Action ..............................................................431 9.3 Handles for Single-Handled Tools..........................................................432 9.3.1 Handle Length...............................................................................432 9.3.2 Handle Diameter...........................................................................432 9.3.3 Handle Shape.................................................................................433 9.3.4 Texture and Materials...................................................................435 9.3.5 Angulation of Handle ..................................................................435 9.4 Handles for Two-Handled Tools.............................................................436 9.4.1 Grip Span........................................................................................436 9.4.2 Gender.............................................................................................438 9.4.3 Handedness....................................................................................438 9.5 Other Tool Considerations .......................................................................439 9.5.1 Posture ............................................................................................439 9.5.2 Weight .............................................................................................439 9.5.3 Gloves..............................................................................................440 9.5.4 Vibration .........................................................................................440 9.5.5 Rhythm............................................................................................440 9.5.6 Miscellaneous.................................................................................440 9.6 Agricultural and Forestry Tools ..............................................................441 9.6.1 Shovels and Spades ......................................................................441 9.6.2 Axes and Hammers ......................................................................446 9.6.3 Saws.................................................................................................450 9.6.4 Other Agricultural Tools ..............................................................451 9.7 Industrial Tools ..........................................................................................452 9.7.1 Pliers ................................................................................................452 9.7.2 Screwdrivers...................................................................................453 9.7.3 Knives..............................................................................................454 9.7.4 Meat Hooks....................................................................................455 9.7.5 Power Tools....................................................................................457 9.7.6 Railroad Tools ................................................................................460 9.7.7 Mining Tools ..................................................................................461 9.7.8 Miscellaneous Tools ......................................................................461 Questions..............................................................................................................463 Problems...............................................................................................................464 References.............................................................................................................464 10 The Office Environment............................................................. 473 10.1 General Musculoskeletal Problems.........................................................473 10.2 The Seated Workplace...............................................................................474 10.2.1 Seated Posture................................................................................474 10.2.2 Seated Posture at a Computer Workstation .............................479 10.2.3 Determination of Seated Comfort ..............................................484 10.2.4 Seat Pressure ..................................................................................487 10.2.5 Sit-Stand, Forward-Sloping, and Saddle Chairs ......................490 10.2.6 Work Surface and Line of Sight..................................................495 10.3 The Keyboard.............................................................................................501 10.3.1 Standard Keyboard Features.......................................................501 10.3.2 Split and Sloped Keyboards........................................................506 10.3.3 Layout of Keys...............................................................................509 10.3.4 Chord Keyboards .......................................................................... 511 10.3.5 Numeric Keypads ......................................................................... 511 10.4 The Mouse and Other Cursor-Positioning Devices.............................513 10.4.1 Cursor Positioning ........................................................................513 10.4.2 The Mouse......................................................................................514 10.4.3 Mouse Alternatives .......................................................................517 10.5 Notebooks and Handheld PCs................................................................518 10.6 Control Measures.......................................................................................519 10.6.1 Rest Pauses.....................................................................................519 10.6.2 Exercises..........................................................................................520 Questions..............................................................................................................522 References.............................................................................................................523 Glossary ................................................................................................ 541 Name Index .......................................................................................... 571 Subject Index ....................................................................................... 591