What is the anaerobic threshold?

• A. The maximum rate of oxygen uptake
• B. The point where anaerobic metabolism begins to supplement aerobic metabolism
• C. The point at which fatigue occurs
• D. The threshold at which the body shifts from aerobic to predominantly anaerobic energy supply

Answer: (D)

An anaerobic threshold is the exercise intensity at which energy supply shifts from primarily aerobic to primarily anaerobic. Before this point, the body's oxygen-delivering systems can keep up with energy demand through aerobic metabolism; after crossing it, anaerobic glycolysis contributes more, lactate builds up, and sustained effort becomes harder. This description captures the moment when the body moves from relying mainly on aerobic pathways to predominantly anaerobic ones, which is what the threshold signifies. It's the concept athletes use to set training zones and pace efforts, often linked with lactate thresholds used in performance testing.