After a bout of exhaustive exercise, oxygen consumption remains elevated above resting values for some time. Which process accounts for the largest portion of this excess postexercise oxygen consumption?
- A Conversion of lactate to glucose exclusively within contracting muscle fibers
- B Regeneration of phosphocreatine depleted during contraction ✓
- C Sustained elevation of thyroid hormone secretion
- D Continued anaerobic ATP production by accumulated lactate
Correct answer: B. Regeneration of phosphocreatine depleted during contraction
Explanation
The oxygen debt, now termed excess postexercise oxygen consumption, reflects restoration of energy stores: resynthesis of phosphocreatine, oxidative metabolism of lactate via gluconeogenesis in liver and kidney, and replenishment of myoglobin and hemoglobin oxygen stores. Phosphocreatine regeneration is the fastest and largest component. Lactate clearance occurs mainly in liver through the Cori cycle, not within the fatigued fibers themselves, and lactate cannot generate ATP anaerobically.
Reference: Guyton and Hall Textbook of Medical Physiology, 14th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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