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

  1. Identify factors affecting maximal performance.

  2. Provide evidence for and against the central nervous system being a site of fatigue.

  3. Identify potential neural factors in the periphery that may be linked to fatigue.

  4. Explain the role of cross-bridge cycling in fatigue.

  5. Summarize the evidence on the order of recruitment of muscle fibers with increasing intensities of activity and the type of metabolism upon which each is dependent.

  6. Describe the factors limiting performance in all-out activities lasting less than ten seconds.

  7. Describe the factors limiting performance in all-out activities lasting 10–180 seconds.

  8. Discuss the subtle changes in the factors affecting optimal performance as the duration of a maximal performance increases from three minutes to four hours.


Sites of Fatigue

  • Central Fatigue

  • Peripheral Fatigue

  • Both Central and Peripheral Fatigue

Factors Limiting All-Out Anaerobic Performances

  • Ultra Short-Term Performances (Ten Seconds or Less)

  • Short-Term Performances (10–180 Seconds)

Factors Limiting All-Out Aerobic Performances

  • Moderate-Length Performances (3–20 Minutes)


  • Performances (21–60 Minutes)

  • Long-Term Performances (1–4 Hours)

Athlete as Machine

Key Terms

central fatigue

peripheral fatigue

free radicals

In the last few chapters, we focused on proper exercise and nutrition for health and fitness. The emphasis was on moderation to reduce the risk factors associated with a variety of diseases. We must now change that focus to discuss the factors limiting physical performance.

Performance goals require much more time, effort, and an elevated risk of injury as compared to fitness goals. What are the requirements for optimal performance? To answer this question, we must ask another: What kind of performance? It is clear that the requirements for the best performance in the 400-m run are different from those associated with the marathon. Figure 19.1 shows a diagram of factors influencing performance (8). Every performance requires a certain amount of strength, as well as the “skill” to apply that strength in the best way. Further, energy must be supplied in the manner needed or performance will suffer. Different activities require differing amounts of energy from aerobic and anaerobic processes. Both the environment (altitude and heat) and diet (carbohydrate and water intake) play a role in endurance performance. In addition, the best performances require a psychological commitment to “go for the gold.”

Figure 19.1

Factors affecting performance.

Beginning with the topic of fatigue, the purpose of this chapter is to expand on the concepts outlined in Figure 19.1 and to discuss the key factors limiting performance in a variety of activities. This understanding serves as the foundation for the Physiology of Performance section of the text.


Fatigue is simply defined as an inability to maintain a power output or force during repeated muscle contractions, which is ...

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