During a 15-second sprint, which energy system is predominantly used?

• A. Glycolytic system
• B. Oxidative system
• C. ATP-PC (Phosphagen) system
• D. Respiratory energy system

Answer: (C)

Short, high‑intensity efforts rely on the phosphagen system because it can rapidly supply ATP without needing oxygen. The phosphocreatine stored in muscles donates a phosphate to ADP to rebuild ATP in a flash, which is exactly what a 15‑second sprint demands. While these stores are limited, they provide the majority of energy in the early part of the sprint, allowing maximal power output to be maintained for the initial seconds. As the effort continues toward the 15‑second mark, glycolysis starts to contribute more, but the phosphagen system still predominates for that brief, intense bout. The oxidative (aerobic) system is slow to engage for such a short effort and plays a much smaller role here, while the glycolytic system becomes more important as durations extend beyond this short window.