Which two energy systems are classified as anaerobic?

• A. Phosphagen (phosphocreatine) system and lactic acid (glycolytic) system
• B. Phosphagen and oxidative phosphorylation
• C. Lactic acid and oxidative phosphorylation
• D. Lipolysis and glycolysis

Answer: (A)

Anaerobic energy production means ATP is generated without relying on oxygen. The phosphagen system provides immediate energy from stored phosphocreatine for very short, high‑intensity efforts. Once those stores are used up, the glycolytic (lactic acid) system takes over, breaking down glucose to ATP and producing lactate when oxygen is limited, which supports high‑intensity work a bit longer. In contrast, oxidative phosphorylation requires oxygen and powers longer, endurance activities. Lipolysis refers to fat breakdown feeding into aerobic fat oxidation, not an anaerobic energy system. So the two anaerobic systems are the phosphagen and glycolytic systems.