Which energy system is primarily used during sustained, moderate-intensity running?

Which energy system is primarily used during sustained, moderate-intensity running?

• A. Glycolytic system
• B. Phosphagen system
• C. Oxidative system
• D. Lactic acid system

Answer: (C)

Sustained, moderate-intensity running relies on aerobic metabolism to meet energy demands over time. The oxidative system uses oxygen and runs in the mitochondria, efficiently producing ATP from fats and carbohydrates for longer durations. Because the pace is steady, the body can supply enough oxygen to keep this system working, making it the primary source of energy for a long, steady run. The other systems are geared for shorter, more intense efforts: the phosphagen system provides immediate energy for very short bursts (about 10 seconds or less) and cannot sustain activity; the glycolytic (lactic acid) system ramps up ATP production quickly but leads to lactate buildup and fatigue, making it less suitable for prolonged effort.

Sustained, moderate-intensity running relies on aerobic metabolism to meet energy demands over time. The oxidative system uses oxygen and runs in the mitochondria, efficiently producing ATP from fats and carbohydrates for longer durations. Because the pace is steady, the body can supply enough oxygen to keep this system working, making it the primary source of energy for a long, steady run. The other systems are geared for shorter, more intense efforts: the phosphagen system provides immediate energy for very short bursts (about 10 seconds or less) and cannot sustain activity; the glycolytic (lactic acid) system ramps up ATP production quickly but leads to lactate buildup and fatigue, making it less suitable for prolonged effort.