During the alactic stage, which energy system is primarily restored?

• A. Aerobic system
• B. Glycolytic system
• C. ATP-PC system
• D. Fat oxidation

Answer: (C)

The alactic stage is defined by immediate, high‑intensity effort using the body’s phosphagen system. This path provides energy very quickly by using stored ATP and phosphocreatine (PC) to regenerate ATP as it’s consumed, allowing short bursts of activity (roughly up to 10 seconds) without producing lactate. Because phosphocreatine stores are limited, this energy supply is brief, and the system is the one that is rapidly “restored” between bursts by processes that primarily involve aerobic metabolism. In contrast, for longer efforts glucose via glycolysis, or fat oxidation for low‑intensity endurance, become more important. So the ATP‑PC system is the best answer because it powers the alactic, immediate energy requirement.