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HMS, BM EQ-Bank 756 MC

During a marathon, which statement accurately describes what happens to an athlete's fuel usage after approximately 2 hours of running?

  1. The athlete continues to rely exclusively on the ATP-PCr system
  2. The glycolytic system becomes the predominant energy provider
  3. The body shifts from predominantly using glycogen to using more fat
  4. Protein becomes the primary fuel source for ATP production
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\(C\)

Show Worked Solution
  • C is correct:
    • During a marathon, after approximately 2 hours of running, glycogen stores become depleted.
    • This causes the body to shift from predominantly using glycogen to increasingly relying on fat as a fuel source.

Other Options:

  • A is incorrect: The ATP-PCr system is only predominant for activities lasting 1-10 seconds, not endurance events like marathons.
  • B is incorrect: The glycolytic system is dominant for activities lasting 30-45 seconds, not for prolonged endurance events.
  • D is incorrect: While protein can be used as a fuel source in the aerobic system, it is not the primary fuel source, even in prolonged exercise; fat becomes the primary alternative fuel once glycogen is depleted.