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  1. Explain the key bioenergetic concepts that are fundamental to energy metabolism.

  2. Describe the general energy pathways and their fundamental differences.

  3. Explain the mechanics of each energy pathway.

  4. Describe adenosine triphosphate (ATP) generation for each energy pathway.

  5. Identify the molecules used as substrate during exercise at different intensities.

  6. Describe the function of specific enzymes in cellular biochemical reactions.

  7. Identify the rate-limiting enzyme for each energy pathway.

  8. Identify the ATP total produced from carbohydrate and lipid metabolism.

  9. Explain the factors that contribute to fatigue with each energy pathway.

  10. Describe the integrated function of the energy systems.

  11. Explain key sex differences regarding the energy pathways.

  12. Identify the effects of aging on the energy pathways.


Visit DavisPlus at for study and practice resources, including online quizzes, animations that help explain physiological processes, podcasts concerning news and career trends in exercise physiology, and practice references.



  • Felicia Rodriguez is a doctoral student in exercise science and is teaching an undergraduate-level course as part of her studies. While preparing to teach her students about bioenergetics, she remembers the confusion that she and her classmates experienced when first learning about the various energy pathways and which nutrients serve as the primary fuel during different forms of physical activity. Once Felicia was able to understand the difference between activities fueled mainly by carbohydrate sources (i.e., high-intensity, short-duration activities that primarily call upon the anaerobic energy systems) versus those fueled by an increased proportion of free-fatty acids (i.e., low- to moderate-intensity, long-duration activities that mainly rely on the aerobic energy pathway), she fared much better in her studying efforts.

    What real-world examples can Felicia use to illustrate this complex topic to her students?

  • After presenting a series of lectures on the rather complex science required to understand the bioenergetics of exercise, Felicia simplifies things by going back to the basics, telling her students that the process of digestion breaks the macronutrients into their simplest components (i.e., glucose, fatty acids, and amino acids), which are absorbed into the blood and transported to metabolically active cells, such as nerve or muscle cells. These substances either immediately enter a metabolic pathway to produce ATP or are stored for later use.

    To clarify how the human body uses the three energy systems—phosphagen, anaerobic glycolysis, and aerobic—Felicia discusses physical activities with which her students are familiar.

  • 100-m run: This activity derives approximately 50% of the fuel needed from the phosphagen system and 50% from the anaerobic glycolysis system, with an insignificant contribution from the aerobic system. This is because a rapid production of ATP is required to fuel this high-intensity, shortduration activity.

  • 10,000-m run: In contrast, this low-intensity, long-duration activity derives 97% of the fuel needed from the aerobic system and only 3% from the anaerobic glycolysis system.

  • Soccer game: A soccer game is a perfect example of how most activities and sports require a combination ...

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