What term describes the amount of oxygen required after exercise to convert accumulated lactic acid back into glucose?

• A. Lactic acid buildup
• B. Oxygen debt
• C. Oxygen surplus
• D. Aerobic threshold

Answer: (B)

The concept here is oxygen debt: after intense activity, the body must take in extra oxygen to convert accumulated lactate back into glucose and to restore other systems to pre-exercise levels. When muscles work hard, they rely on anaerobic metabolism that produces lactic acid, increasing the need for oxygen once you stop to clear that lactate and replenish energy stores. The amount of oxygen used above resting levels to repay that temporary imbalance is what we call the oxygen debt, sometimes referred to as excess post-exercise oxygen consumption. This explains why you continue to breathe hard after stopping exercise—the body is paying back the oxygen shortfall created during activity. Lactic acid buildup describes the accumulation itself, not the repayment; an oxygen surplus isn’t the concept here, and the aerobic threshold relates to the intensity at which aerobic metabolism predominates, not lactate clearance.