AFAA Personal Trainer Certification Practice Exam

What resource does the aerobic energy system primarily utilize for fuel?

1. Sugars only

2. Fat only

3. Carbohydrates, fats, and proteins

4. Only carbohydrates

The correct answer is: Carbohydrates, fats, and proteins

The aerobic energy system primarily utilizes carbohydrates, fats, and proteins as fuel sources when generating energy. This system operates during prolonged, moderate-intensity activities where oxygen is available to help convert these macronutrients into energy. Carbohydrates are a quick source of energy and are often emphasized during higher intensity exercise, while fats provide a more substantial energy source during lower intensity, longer durations. Proteins can also serve as energy, though they are primarily utilized during prolonged exercise or when carbohydrate stores are depleted. This comprehensive utilization of energy substrates distinguishes the aerobic system from anaerobic pathways, which rely primarily on carbohydrates for quick bursts of energy without oxygen. Therefore, the correct answer reflects the versatility of the aerobic energy system in using multiple macronutrients for sustained energy production.