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After studying this chapter, the reader should be able to:

  • 6.1 Trace the pathway of a food starting with consumption and ending with usable energy.

  • 6.2 Outline the metabolic pathways including the phosphagen system, anaerobic glycolysis, aerobic glycolysis, and fatty acid oxidation as they relate to exercise performance.

  • 6.3 Explain how energy is stored in the skeletal muscles and other tissues, and how other nutrients are delivered via the digestion and absorption system.

  • 6.4 Apply energy metabolism to design of nutrition strategies for active individuals and populations.


  • aerobic respiration The 10-step metabolic process of breaking glucose down to intermediate pyruvate, which is converted to acetyl-CoA and enters the citric acid cycle. Occurs in the mitochondria and cytoplasm in the presence of oxygen; produces a net 36 adenosine triphosphate (ATP).

  • anaerobic respiration The 10-step metabolic process of breaking glucose down to intermediate pyruvate and then lactic acid; occurs in the cytoplasm of cells; produces a net 2 adenosine triphosphate (ATP).

  • anaerobic threshold Point in exercise when lactate accumulation begins. Also known as lactate threshold or ventilatory threshold.

  • beta oxidation The process in which carbon fragments are removed from the fatty acid. These carbon molecules produce acetyl-CoA, which enters the citric acid cycle and electron transport chain.

  • bioenergetics The process of studying the capture, conversion, and use of energy from ATP.

  • cardiac output The volume of blood pumped through the heart per minute (mL blood/min); calculated as stroke volume (mL blood/beat) × heart rate (beat/min).

  • citric acid cycle A metabolic pathway involved in the chemical conversion of carbohydrates, fats, and proteins into carbon dioxide and water to generate a form of usable energy. Also known as Krebs cycle and tricarboxylic acid cycle.

  • creatine phosphate An important source of stored energy; its breakdown to creatine plus a high-energy phosphate can rapidly fuel the first 5 to 10 seconds of exercise.

  • cross-bridge cycle The process whereby a series of molecular actions cause myosin and actin to interact and produce muscle contraction.

  • electron-transport chain The process of stripping NADH and FADH of their hydrogen molecules through a series of chemical reduction-oxidation reactions, which ultimately powers the conversion of adenosine diphosphate (ADP) plus Pi to ATP and provides energy to the working cell.

  • excess post-exercise oxygen consumption (EPOC) The elevated oxygen consumption after high-intensity exercise has stopped.

  • flavin adenine dinucleotide (FADH) A hydrogen-carrying molecule that enters the electron transport chain to produce 2 ATPs per molecule of FADH.

  • gluconeogenesis The production of glucose from precursors in the liver.

  • glycolysis The process through which glucose is converted to pyruvate.

  • Krebs cycle See citric acid cycle.

  • lactate A salt of lactic acid produced in the body.

  • lactate threshold Point in exercise when lactate accumulation begins. Also known as anaerobic threshold or ventilatory threshold.

  • lactic acid A metabolic byproduct of anaerobic glucose metabolism.

  • lipogenesis The production of fat from excess carbohydrate, protein, or fat that is consumed beyond what the body immediately can use for energy, structural support, or ...

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