Which energy system is primarily used for prolonged, low-intensity exercise?

Which energy system is primarily used for prolonged, low-intensity exercise?

• A. ATP-PC system
• B. Aerobic system
• C. Lactic acid system
• D. Aerobic glycolysis

Answer: (B)

For prolonged, low‑intensity exercise, the body relies mainly on the aerobic energy system. This system uses oxygen to generate ATP through oxidative phosphorylation in the mitochondria, allowing a steady and large supply of energy for long durations. It can use both fats and carbohydrates as fuel, which helps sustain activity for extended periods without rapid fatigue. The other systems are suited to different demands. The ATP‑PC system provides immediate energy for very short bursts (about ten seconds or less) and is exhausted quickly. The lactic acid system (anaerobic glycolysis) pumps out energy quickly for higher-intensity efforts but produces lactate and can’t be sustained for long. Aerobic glycolysis is a part of the aerobic process, occurring when glucose is used with oxygen, but the overall energy source for long, steady work is the aerobic system.

For prolonged, low‑intensity exercise, the body relies mainly on the aerobic energy system. This system uses oxygen to generate ATP through oxidative phosphorylation in the mitochondria, allowing a steady and large supply of energy for long durations. It can use both fats and carbohydrates as fuel, which helps sustain activity for extended periods without rapid fatigue.

The other systems are suited to different demands. The ATP‑PC system provides immediate energy for very short bursts (about ten seconds or less) and is exhausted quickly. The lactic acid system (anaerobic glycolysis) pumps out energy quickly for higher-intensity efforts but produces lactate and can’t be sustained for long. Aerobic glycolysis is a part of the aerobic process, occurring when glucose is used with oxygen, but the overall energy source for long, steady work is the aerobic system.