1;Foreword;6 2;Preface;8 3;Contents;10 4;Contents to Muscle Pain: Diagnosis and Treatment;12 5;Contributors;14 6;1: Introduction;16 6.1;Subjective Nature of Pain Terms;17 6.2;Established Pain Terms (partly after Merskey and Bogduk 1994; Loeser and Treed;18 6.2.1;General Terms;18 6.2.1.1;Nociception;18 6.2.1.2;Noxious Stimulus;18 6.2.1.3;Nociceptor;18 6.2.1.4;Nociceptive Neuron;19 6.2.1.5;Pain Matrix;19 6.2.1.6;Central Pain;19 6.2.2;Increased Sensitivity;19 6.2.2.1;Allodynia;19 6.2.2.2;Hyperalgesia;19 6.2.2.3;Hyperesthesia;19 6.2.2.4;Hyperpathia;20 6.2.3;Decreased Sensitivity;20 6.2.3.1;Analgesia;20 6.2.3.2;Hypoalgesia;20 6.3;Established, But Often Ill-Defined, Pain Terms;20 6.3.1;Contracture (in the Physiological Sense);20 6.3.2;Muscle Spasm;20 6.3.3;Muscle Stiffness;21 6.3.4;Muscle Tone;21 6.3.5;Projected Pain;21 6.3.6;Referred Pain;21 6.3.7;Spread of Pain;22 6.4;General Aspects of Pain and Nociceptor Function;22 6.5;Muscle Pain Versus Skin Pain;23 6.5.1;Subjective Differences;24 6.5.1.1;First and Second Pain;24 6.5.1.2;Pain Localization;24 6.5.1.3;Nature of Pain;25 6.5.1.4;Referral of Pain;25 6.5.1.5;Affective Pain Component;26 6.5.2;Objective Differences;26 6.5.2.1;Flexion Reflexes;26 6.5.2.2;Differences in Synaptic Effectiveness and CNS Targets of Afferent Fibers;27 6.6;Descending Pain-Modulating Influences;28 6.7;Transition from Acute to Chronic Pain;28 6.8;Interactions Between Psychosocial and Somatic Factors;28 6.9;References;29 7;2: Functional Anatomy of Muscle: Muscle, Nociceptors and Afferent Fibers;31 7.1;Structure and Basic Function of Skeletal Muscle;32 7.2;Morphology of Muscle Nociceptors;39 7.2.1;Structure of Muscle Nociceptors in the Light and Electron Microscope;39 7.2.2;Receptor Molecules in the Membrane of Nociceptors;42 7.2.3;Neuropeptide Content of Nociceptors;47 7.3;The Nociceptive Afferent Fiber;49 7.4;Fiber Composition of a Muscle Nerve;51 7.5;Muscle Receptors Other Than Nociceptors;53 7.6;Free Nerve Endings in Tendon;54 7.7;Free Nerve Endings in Fascia;55 7.8;Efferent Functions of Nociceptors;55 7.8.1;Release of Neuropeptides from the Nociceptive Ending;55 7.8.2;The Axon Reflex;57 7.8.3;Neurogenic Inflammation;58 7.9;References;59 8;3: Peripheral Mechanisms of Muscle Pain: Response Behavior of Muscle Nociceptors and Factors Eliciting Local Muscle Pain;63 8.1;Methods Used for Studying the Response Behavior of Single Group III and IV Muscle Afferent Units;64 8.1.1;General Response Properties of Muscle Nociceptors;67 8.2;Stimuli Exciting Muscle Nociceptors;68 8.2.1;Mechanical Stimuli;68 8.2.2;Chemical Stimuli;71 8.2.2.1;General Considerations;71 8.2.2.2;ATP;72 8.2.2.3;Protons;72 8.2.2.4;Endogenous Inflammatory Substances;74 8.2.2.5;Hypertonic Saline;75 8.2.2.6;Cytokines and Neurotrophins;78 8.2.2.7;Glutamate;80 8.2.2.8;General Considerations Concerning the Chemical Excitability of Free Nerve Endings in Muscle;81 8.2.3;Polymodal Nociceptors;82 8.3;Acute Sensitization of Nociceptors;84 8.3.1;General Features of Peripheral Sensitization;84 8.3.2;Mechanical Sensitization by Endogenous Substances;85 8.3.3;Interactions Between Chemical Stimuli at the Receptive Nerve Ending;90 8.3.4;Responses of Free Nerve Endings in Muscle to Ischemia and Ischemic Contractions;91 8.3.4.1;Effects of Ischemia Without Contractions;91 8.3.4.2;Ischemic Contractions;92 8.3.5;Effects of Inflammatory Tissue Changes on the Activity of Muscle Group IV Units;95 8.3.5.1;Resting Discharge;96 8.3.5.2;Inflammation-Induced Mechanical Sensitization;97 8.3.5.3;Effectiveness of Chemical Stimulants in Chronically Inflamed Muscle;100 8.4;How Do Muscle Spindle Afferents Behave in Inflamed Muscle?;102 8.5;Effects of a Chronic Muscle Lesion on the Innervation of Skeletal Muscle;103 8.6;Response Properties and Possible Functions of Nonnociceptive Free Nerve Endings in Muscle;104 8.7;Local Causes of Muscle Pain;105 8.7.1;Mechanical Causes;105 8.7.1.1;Blow to Muscle;105 8.7.1.2;Rupture of Muscle and Tendon;106 8.7.1.3;Spontaneous Hematoma;107 8.7.1.4;Del