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At the completion of this chapter, the reader will be able to:

  1. Outline the various roles of human skeletal muscle.

  2. List the various roles of muscle in the human body.

  3. Differentiate among muscle strength, endurance, and power.

  4. Understand the importance of manual muscle testing.

  5. Perform a gross muscle screening of a patient’s strength.

  6. Perform specific manual muscle tests on the various muscles of the body.

  7. Define delayed onset muscle soreness (DOMS) and explain why it occurs.

  8. Describe the concept of specificity of training.

  9. Describe strategies to increase muscle strength, endurance, and power.

  10. List the different types of resistance that can be used to improve muscle performance.

  11. Outline the various types of exercise progression and the components of each.

  12. Explain the basic principles behind plyometrics.



Movement of the body or any of its parts involves considerable activity from those muscles directly responsible. Muscle is the only biological tissue capable of actively generating tension. This characteristic enables the human skeletal muscle to perform the important functions of maintaining upright body posture, moving body parts, and absorbing shock. For functional body motions to occur, the performing muscles must have a stable base from which to work. If a functional limitation is highlighted during the physical examination, the clinician must determine the cause. If the cause is poor muscle performance, a progression of exercises to enhance muscle performance must be initiated. One of the most common ways of improving muscle performance is through graded resistance exercises, which can be applied globally or locally. The clinician must remember that several factors influence a patient’s ability to exercise. These factors can include fear of pain or reinjury, poor motivation, low compliance, depression, medication side effects, and impaired attention or memory.


The ability of a muscle to carry out its various roles is a measure of muscle performance. The three main types of muscle contractions are isometric, concentric (Fig. 12-1A and B), and eccentric (Fig. 12-2A and B) (see Chapter 1). Muscle performance can be assessed by measuring several parameters. These include strength, endurance, and power.

  • Strength. The improvement of muscle strength is an integral component of most rehabilitation programs. Strength may be defined as the amount of force that an individual exerts in a single maximum muscular contraction against a specific resistance or the ability to produce torque at a joint. Strength can be measured in three ways: the maximal force exerted in an isometric contraction, the maximum load lifted once, or the peak torque during isokinetic measurement. In a clinical setting, muscle strength can be measured as follows:

    • Manual muscle testing (MMT): MMT is an acceptable standardized process utilized to find gross strength deficits and isolate muscle groups and actions (see later).

    • Using a dynamometer: Dynamometry is the process of measuring forces that are doing ...

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