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OBJECTIVES

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By studying this chapter, you should be able to do the following:

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  1. Draw and label the microstructure of a skeletal muscle fiber.

  2. Define satellite cells. What role do satellite cells play in muscle repair from injury?

  3. List the chain of events that occur during muscular contraction.

  4. Define both dynamic and static exercise. What types of muscle action occur during each form of exercise?

  5. Describe the three factors that determine the amount of force produced during muscular contraction.

  6. Compare and contrast the major biochemical and mechanical properties of the three primary types of muscle fibers found in human skeletal muscle.

  7. Describe how skeletal muscle fiber types influence athletic performance.

  8. Graph and describe the relationship between movement velocity and the amount of force exerted during muscular contraction.

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OUTLINE

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  • Structure of Skeletal Muscle 167

  • Neuromuscular Junction 170

  • Muscular Contraction 171

    • Overview of the Sliding Filament/Swinging Lever-Arm Model 171

    • Energy for Contraction 173

    • Regulation of Excitation-Contraction Coupling 173

  • Exercise and Muscle Fatigue 177

  • Exercise-Associated Muscle Cramps 177

    • Exercise-Associated Muscle Cramps Are Not Caused by Dehydration or Electrolyte Imbalance 177

    • Exercise-Associated Muscle Cramps Are Likely Due to Changes in the Central Nervous System 178

    • Exercise-Associated Muscle Cramps: Conclusions 178

  • Muscle Fiber Types 180

    • Overview of Biochemical and Contractile Characteristics of Skeletal Muscle 180

    • Functional Characteristics of Muscle Fiber Types 181

    • Fiber Types and Performance 183

  • Muscle Actions 184

  • Speed of Muscle Action and Relaxation 185

  • Force Regulation in Muscle 185

  • Force-Velocity/Power-Velocity Relationships 187

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KEY TERMS

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actin

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concentric action

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dynamic

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eccentric action

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endomysium

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end-plate potential (EPP)

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epimysium

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extensors

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fascicle

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fast-twitch fibers

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flexors

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intermediate fibers

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isometric action

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lateral sac

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motor neurons

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motor unit

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muscle action

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myofibrils

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myosin

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neuromuscular junction (NMJ)

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perimysium

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postactivation potentiation (PAP)

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sarcolemma

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sarcomeres

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sarcoplasmic reticulum

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satellite cells

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sliding filament model

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slow-twitch fibers

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summation

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swinging lever-arm model

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terminal cisternae

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tetanus

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transverse tubules

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tropomyosin

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troponin

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twitch

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type I fibers

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type IIa fibers

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type IIx fibers

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INTRODUCTION

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The human body contains more than 600 skeletal muscles, which constitute 40% to 50% of the total body weight (61). Skeletal muscle performs three important functions: (1) force generation for locomotion and breathing, (2) force generation for postural ...

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