Which energy system is used during low-intensity exercise?

• A. ATP-PC system
• B. Anaerobic/Lactic acid system
• C. Aerobic system
• D. Oxygen debt

Answer: (C)

Low-intensity exercise relies on aerobic metabolism because the body can deliver enough oxygen to the working muscles to meet the energy demand. In the aerobic system, glucose and fats are broken down in the mitochondria using oxygen to produce ATP, which can fuel activity for longer periods without quickly causing fatigue. While this system works slower than the immediate energy you get from the ATP-PC system, it lasts much longer, making it ideal for sustained, easy to moderate efforts. The ATP-PC system provides energy for very short, explosive bursts (about up to 10 seconds) and the anaerobic/lactic system becomes important at higher intensities when oxygen delivery can’t keep up, producing lactate. Oxygen debt is about the extra oxygen needed after exercise to recover, not the energy source during the activity. So, for low-intensity work, the aerobic system is the main supplier of energy.