During a marathon, which energy system provides prolonged ATP production?

• A. ATP-PCr system
• B. Lactic acid system
• C. Aerobic system
• D. Glycolysis

Answer: (C)

Prolonged ATP production comes from the aerobic energy system. In a marathon, the pace is steady and endurance-based, so the body relies on oxygen to drive ATP production over many minutes to hours. This system uses mitochondria to oxidize fuels (carbohydrates and fats) and yields a large amount of ATP, enough to sustain activity for long durations.

The other options are suited to shorter, high-intensity efforts. The ATP-PCr system provides immediate energy for roughly the first 10 seconds of maximal effort and then rapidly depletes. The lactic acid system (anaerobic glycolysis) can supply ATP quickly but only for a couple of minutes before fatigue from lactate accumulation limits performance. Glycolysis itself is a pathway feeding both anaerobic and aerobic energy production, but the prolonged, steady energy for a marathon is dominated by the aerobic (oxidative) process.