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

  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 and explain 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.


Structure of Skeletal Muscle

Neuromuscular Junction

Muscular Contraction

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

Energy for Contraction 184 Regulation of Excitation-Contraction Coupling

Exercise and Muscle Fatigue

Exercise-Associated Muscle Cramps

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

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

  • Exercise-Associated Muscle Cramps: Conclusions

Muscle Fiber Types

  • Overview of Biochemical and Contractile Characteristics of Skeletal Muscle

  • Functional Characteristics of Muscle Fiber Types

  • Fiber Types and Performance

Muscle Actions

Speed of Muscle Action and Relaxation

Force Regulation in Muscle

Force-Velocity/Power-Velocity Relationships

Key Terms


concentric action


eccentric action


end-plate potential (EPP)




fast-twitch fibers


intermediate fibers

isometric action

lateral sac

motor neurons

motor unit

muscle action



neuromuscular junction (NMJ)



potentiation (PAP)



sarcoplasmic reticulum

satellite cells

sliding filament model

slow-twitch fibers


swinging lever-arm model

terminal cisternae


transverse tubules




type I fibers

type IIa fibers

type IIx fibers

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 support, and (3) heat production during cold stress. The most obvious function of skeletal muscle is to enable an individual to move freely and breathe. New evidence also suggests that skeletal muscles are endocrine organs and play an important role in the regulation of a variety of organ systems in the body. This concept was introduced in Chap. 5 and will be mentioned again in this chapter.

Skeletal muscles are attached to bones by connective tissue called tendons. One end of the muscle is attached to a bone that does not move (origin), and the opposite end is fixed to a bone (insertion) that is moved during muscular contraction. A variety of different movements are possible, depending on the type of joint and muscles involved. Muscles that decrease joint angles are called flexors, and muscles that increase joint angles are called extensors.


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