During submaximal endurance exercise, which energy system predominates?

During submaximal endurance exercise, which energy system predominates?

• A. Pure anaerobic glycolysis
• B. Oxidative (aerobic) metabolism
• C. Immediate phosphocreatine
• D. Protein oxidation

Answer: (B)

At submaximal endurance, the body relies primarily on aerobic metabolism to supply ATP. This sustained, moderate-intensity work uses oxygen to fuel the mitochondria, converting carbohydrates and fats into ATP over longer periods. Because oxygen delivery can meet the ongoing energy demand, the oxidative (aerobic) pathway becomes the dominant source, supporting prolonged activity with a high yield of ATP per fuel molecule. The immediate phosphocreatine system provides quick energy only for the first few seconds and is exhausted rapidly, while anaerobic glycolysis contributes more when intensity is higher and can lead to lactate buildup that isn’t sustainable for long durations. Protein oxidation is negligible under normal endurance conditions.

At submaximal endurance, the body relies primarily on aerobic metabolism to supply ATP. This sustained, moderate-intensity work uses oxygen to fuel the mitochondria, converting carbohydrates and fats into ATP over longer periods. Because oxygen delivery can meet the ongoing energy demand, the oxidative (aerobic) pathway becomes the dominant source, supporting prolonged activity with a high yield of ATP per fuel molecule. The immediate phosphocreatine system provides quick energy only for the first few seconds and is exhausted rapidly, while anaerobic glycolysis contributes more when intensity is higher and can lead to lactate buildup that isn’t sustainable for long durations. Protein oxidation is negligible under normal endurance conditions.