5

Pr~face xv

What is Biomechanics?2

2

i)ipmechanics: Definitipn and PerspectivePr.oblemsStudied by Bi.omechanists 4Why Study Bi.omechanics? 10

Pr.oblem-S.olvingApproach 10Quantitative versus Qualitative Pr.oblemsS.olvingQualitative Pr.oblems 12F.ormalversus Inf.ormalPr.oblems 13

S.olvingF.ormalQuantitative Pr.oblems 13Units .ofMeasurement 14

Summary 17

~inematic Concepts for Analyzing Human Motion

Forms .of M.oti.on 28Linear M.oti.on 28

Angular M.oti.on 29General M.oti.on 29

MechanicalSystems 29Standard Reference Termin.ol.ogy 30

Anat.omicalReference P.ositi.on 30Directi.onalTerms 31Anat.omicalReference Planes 32Anat.omicalReference Axes 32

JOint M.ovement Termin.ol.ogy 35Sagittal Plane M.ovements 35Fr.ontalPlane M.ovements 36Transverse Plane M.ovements 38Other M.ovements 40

Spatial Reference Systems 40Qualitative Analysis .of Human M.ovement 41

Prerequisite Kn.owledgef.ora Qualitative Analysis 41Planninga Qualitative Analysis 43C.onductinga Qualitative Analysis 45

T.o.olsf.or Measuring Kinematic Quantities 48Cinemat.ographyand Vide.ography 48Other M.ovementM.onit.oringSystems 49Other Assessment T.o.ols 49

Summary 51

27

II

3 61~inetic Concepts for Analyzing Human Motion

Basic C.oncepts Related t.o Kinetics 62Inertia 62Mass 63F.orce 63

CONTENTS vii

4

Center of Gravity 64Weight 64Pressure 66Volume 66

Density 68Torque 68Impulse 69

Mechanical Loads on the Human Body 70Compression, Tension, and Shear 70MechanicalStress 71

Torsion, Bending,and Combined Loads 72The Effectsof Loading 73Repetitive versus Acute Loads 74

Tools for Measuring Kinetic Quantities 75Electromyography 75Dynamography 75

Vector Algebra 76Vector Composition 76Vector Resolution 78

Graphic Solution of Vector Problems 78Trigonometric Solution of Vector Problems 79

Summary 80

The Biomechanics of Human Bone Growthand Development 87

Composition and Structure of Bone Tissue 88Material Constituents 88

Structural Organization 88Types of Bones 90

Bone Growth and Development 92LongitudinalGrowth 93Circumferential Growth 93

Adult Bone Development 93Bone Response to Stress 94

Bone Modeling and Remodeling 94Bone Hypertrophy 95Bone Atrophy 96

Osteoporosis 98Postmenopausal and Age-Associated Osteoporosis 98Female Athlete Triad 99

Preventing and Treating Osteoporosis 100Common Bone Injuries 102

Fractures 102

EpiphysealInjuries 104Summary 104

5 The Biomechanics of Human SkeletalArticulations I I7

joint Architecture 118ImmovableJoints I18SlightlyMovableJoints 118

VIII BASIC BIOMECHANICS

Freely Movable Joints I 19Articular Cartilage 121Articular Fibrocartilage 121Articular Connective Tissue 122

joint Stability 123Shapeof the Articulating Bone Surfaces 123Arrangement of Ligaments and Muscles 124Other Connective Tissues 124

joint Flexibility 125Measuring Joint Range of Motion 125Factors Influencing Joint Flexibility 126Flexibility and Injury 128

Techniques for Increasing joint Flexibility 129Neuromuscular Response to Stretch 129Active and PassiveStretching 13IBallistic and Static Stretching 132

Proprioceptive Neuromuscular Facilitation 132Common joint Injuries and Pathologies 134

Sprains 134Dislocations 134Bursitis 134Arthritis 134Rheumatoid Arthritis 134Osteoarthritis 135

Summary 135

6 The Biomechanics of Human Skeletal Muscle

Behavioral Properties of the Musculotendinous UnitExtensibility and Elasticity 146

Irritability and the Ability to Develop Tension 147

Structural Organization of Skeletal Muscle 147Muscle Fibers 148Motor Units 151

Fiber Types 152Fiber Architecture 154

Skeletal Muscle Function 157Recruitment of Motor Units 158

Change in Muscle Length with Tension DevelopmentRoles Assumed by Muscles 159Two-Joint and Multijoint Muscles 160

Factors Affecting Muscular Force Generation 162

Force-Velocity Relationship 162Length-Tension Relationship 163

Stretch-Shortening Cycle 163Electromechanical Delay 165

Muscular Strength, Power, and Endurance 165Muscular Strength 165Muscular Power 168Muscular Endurance 169

145

146

158

Muscle Fatigue 169Effectof MuscleTemperature

Common Muscle Injuries 171Strains 171Contusions 171

Cramps 171Delayed-Onset Muscle SorenessCompartment Syndrome 172

Summary 172

170

171

7 The Biomechanics of the Human UpperExtremity 183Structure of the Shoulder 184

Sternoclavicular joint 184Acromioclavicularjoint 185Coracoclavicular joint 185Glenohumeral joint 185Scapulothoracic joint 187Bursae 188

Movements of the Shoulder Complex 188Muscles of the Scapula 189Muscles of the Glenohumeral joint 190Flexion at the Glenohumeral joint 192Extension at the Glenohumeral joint 192Abduction at the Glenohumeral joint 192Adduction at the Glenohumeral joint 192Medial and lateral Rotation of the Humerus 193

Horizontal Adduction and Abduction at the Glenohumeral jointLoads on the Shoulder 195

Common Injuries of the Shoulder 198Dislocations 198

Rotator Cuff Damage 198Rotational Injuries 200Subscapular Neuropathy 200

Structure of the Elbow 200

Humeroulnar joint 200Humeroradial joint 200Proximal Radioulnar joint 20 I

Movements at the Elbow 202

Muscles Crossing the Elbow 202Flexion and Extension 202

Pronation and Supination 203Loads on the Elbow 205

Common Injuries of the Elbow 207Sprains and Dislocations 207Overuse Injuries 207

Structure of the Wrist 208Movements of the Wrist 209

Flexion 209

CONTENTS IX

194

x BASICBIOMECHANICS

Extension and Hyperextension 210Radial and Ulnar Deviation 210

Structure of the Joints of the Hand 211Carpometacarpal and Intermetacarpal Joints 212MetacarpophalangealJoints 212Interphalangeal Joints 213

Movements of the Hand 21 3

Common Injuries of the Wrist and Hand 215Summary 216

8 The Biomechanics of the Human LowerExtremity 229

Structure of the Hip 230Movements at the Hip 231

Muscles of the Hip 231Flexion 233Extension 234Abduction 234Adduction 235Medial and lateral Rotation of the Femur 235Horizontal Abduction and Adduction 236

Loads on the Hip 236Common Injuries of the Hip 238

Fractures 238Contusions 238Strains 238

Structure of the Knee 239

Tibiofemoral Joint 239Menisci 239

Ligaments 240Patellofemoral Joint 241Joint Capsule and Bursae 241

Movements at the Knee 242

Muscles Crossing the Knee 242Flexion and Extension 243Rotation and PassiveAbduction and Adduction 243

Patellofemoral Joint Motion 244Loads on the Knee 244

Forces at the Tibiofemoral Joint 244Forces at the Patellofemoral Joint 245

Common Injuries of the Knee and Lower Leg 247Anterior Cruciate Ligament Injuries 247Posterior Cruciate Ligament Injuries 248Medial Collateral Ligament Injuries 248ProphylacticKnee Bracing 249Meniscus Injuries 249IliotibialBandFrictionSyndrome 249Breaststroker's Knee 250

Patellofemoral Pain Syndrome 250Shin Splints 251

Structure of the Ankle 251Movements at the Ankle 252Structure of the Foot 254

Subtalar Joint 255Tarsometatarsal and Intermetatarsal Joints 255Metatarsophalangeal and Interphalangeal Joints 255Plantar Arches 255

Movements of the Foot 256Muscles of the Foot 256

Toe Flexion and Extension 256Inversion and Eversion 256

Pronation and Supination 257Loads on the Foot 258

Common Injuries of the Ankle and Foot 259Ankle Injuries 259Overuse Injuries 259

Alignment Anomalies of the Foot 260Injuries Related to High and low Arch Structures 261

Summary 262

9 The Biomechanics of the Human Spine

Structure of the Spine 276Vertebral Column 276

Vertebrae 277Intervertebral Discs 278

Ligaments 282Spinal Curves 283

Movements of the Spine 285Flexion, Extension, and Hyperextension 286lateral Flexion and Rotation 286

Muscles of the Spine 287Anterior Aspect 287Posterior Aspect 290lateral Aspect 293

Loads on the Spine 294

Common Injuries of the Back and Neck 300low Back Pain 300

Soft Tissue Injuries 302Acute Fractures 302Stress Fractures 303Disc Herniations 304

Whiplash Injuries 304

Summary 304

10 Linear Kinematics of Human Movement

Linear Kinematic Quantities 318Distanceand Displacement 319SpeedandVelocity 320

CONTENTS XI

275

317

XII BASIC BIOMECHANICS

Acceleration 325

Average and Instantaneous Quantities 329Kinematics of Projectile Motion 329

Horizontal and Vertical Components 330Influence of Gravity 330Influence of Air Resistance 331

Factors Influencing Projectile Trajectory 332Projection Angle 333Projection Speed 334Relative Projection Height 336Optimum Projection Conditions 337

Analyzing Projectile Motion 338Equations of Constant Acceleration 340

Summary 345

II Angular Kinematics of Human Movement 355

Observing the Angular Kinematics of Human MovementMeasuring Angles 356

Relativeversus Absolute Angles 357Tools for Measuring BodyAngles 358Instant Center of Rotation 360

Angular Kinematic Relationships 360Angular Distance and Displacement 361Angular Speed and Velocity 363Angular Acceleration 366Angular Motion Vectors 369Average versus Instantaneous Angular Quantities 370

Relationships Between Linear and Angular Motion 370Linear and Angular Displacement 370Linear and AngularVelocity 371Linear and AngularAcceleration 373

Summary 376

356

12 Linear Kinetics of Human Movement

Newton's Laws 384Law of Inertia 384Law of Acceleration 384Law of Reaction 385Law of Gravitation 388

Mechanical Behavior of Bodies in Contact 389Friction 389Momentum 395

Impulse 397Impact 399

Work, Power, and Energy Relationships 403Work 403Power 404

Energy 404

383

Conservation of Mechanical Energy 406

Principle of Work and Energy 407

Summary 410

13 Equilibrium and Human Movement

Equilibrium 420Torque 420Resultant joint Torques 423Levers 427

Anatomical Levers 430

Equations of Static Equilibrium 433Equations of Dynamic Equilibrium 434

Center of Gravity 436Locating the Center of Gravity 437Locating the Human Body Center of Gravity 439

Stability and Balance 441Summary 445

14 Angular Kinetics of Human Movement

Resistance to Angular Acceleration 454Moment of Inertia 454

Determining Moment of Inertia 456Human Body Moment of Inertia 457

Angular Momentum 458Conservation of Angular Momentum 461Transfer of Angular Momentum 462Change in Angular Momentum 465

Angular Analogues of Newton's Laws of MotionNewton's First Law 468Newton's Second Law 469Newton's Third Law 469

Centripetal Force 470Summary 471

15 Human Movement in a Fluid Medium

The Nature of Fluids 480Relative Motion 480

Laminar versus Turbulent Flow 482

Fluid Properties 482

Buoyancy 483Characteristics of the Buoyant Force 483Flotation 484

Flotation of the Human Body 484

Drag 486Skin Friction 488

Form Drag 488Wave Drag 492

CONTENTS XIII

419

453

468

479

xiv BASICBIOMECHANICS

Lift Force 493Foil Shape 494Magnus Effect 498

Propulsion in a Fluid Medium 500Propulsive Drag Theory 50 IPropulsive LiftTheory 50 IVortex Generation 50 I

Stroke Technique 502Summary 502

AppendicesA Basic Mathematics and Related Skills 5 I I

B Trigonometric Functions 516

C Common Units of Measurement 519

D Anthropometric Parameters for the Human Body 520

Glossary 523

Index 531