Which energy system predominates during high-intensity exercise lasting between 10 seconds and 3 minutes?

• A. ATP-PC system
• B. Anaerobic/Lactic acid system
• C. Aerobic system
• D. Oxygen debt

Answer: (B)

This question tests which energy system supplies most ATP during high‑intensity effort in the 10 seconds to a few minutes range. When work is very intense but not immediate sprint level, the body can’t get oxygen to the muscles quickly enough, so it relies on anaerobic glycolysis—the lactic acid system. It breaks down glucose to produce ATP rapidly without needing oxygen, which fits this middle ground duration where the ATP-PC system has already been exhausted and the aerobic system isn’t yet the primary supplier. A byproduct is lactate, which contributes to fatigue as the effort continues. Oxygen debt isn’t a system that fuels energy during the activity; it’s the extra oxygen the body uses after the stop to help recovery. So the predominant system in this time frame is the anaerobic/lactic acid system.