The anaerobic glycolysis system contributes most during high‑intensity exercise for what duration?

• A. 10 seconds to 2 minutes
• B. 0–10 seconds
• C. 20–30 minutes
• D. 5–10 minutes

Answer: (A)

During high‑intensity effort, the body uses energy systems in sequence depending on how long the effort lasts. The anaerobic glycolysis system provides ATP quickly without oxygen by breaking down glucose to lactate. It starts to take over after the very brief initial burst supplied by the ATP‑PCr system, which covers roughly the first 0–10 seconds. From about 10 seconds up to around 2 minutes, glycolysis can sustain a high rate of energy production, though lactate accumulation eventually limits its use. Beyond about two minutes, the aerobic system becomes the dominant source of energy. So, the period during which glycolysis contributes most is roughly 10 seconds to 2 minutes, which fits high‑intensity efforts like sprinting slightly longer than a few seconds up to a couple of minutes. Shorter efforts (0–10 seconds) rely more on ATP‑PCr, and much longer efforts (20–30 minutes, 5–10 minutes) rely mainly on aerobic metabolism.