A person riding in a 100-mile bicycle race relies primarily on which energy system to fuel her long ride?

• A. Fermentation
• B. Anaerobic glycolysis
• C. Phosphagen (ATP-PC) system
• D. Aerobic (oxidative) metabolism

Answer: (D)

Verified step by step guidance

1. Understand the energy systems: Begin by reviewing the four main energy systems used by the body to produce ATP (adenosine triphosphate), the molecule that provides energy for cellular processes. These systems are fermentation, anaerobic glycolysis, the phosphagen system, and aerobic metabolism.
2. Analyze the activity type: A 100-mile bicycle race is a prolonged endurance activity that requires sustained energy over several hours. This type of activity primarily relies on energy systems capable of producing ATP efficiently over long durations.
3. Evaluate the energy systems: Fermentation and anaerobic glycolysis are short-term energy systems that provide ATP quickly but are not efficient for prolonged activities. The phosphagen system is used for very short bursts of energy lasting only a few seconds. Aerobic metabolism, on the other hand, is highly efficient and can sustain ATP production for extended periods using oxygen.
4. Connect aerobic metabolism to endurance: Aerobic metabolism uses oxygen to break down carbohydrates, fats, and sometimes proteins to produce ATP. This system is ideal for endurance activities like a 100-mile bicycle race because it provides a steady supply of energy over time.
5. Conclude the reasoning: Based on the type of activity and the characteristics of the energy systems, aerobic metabolism is the primary energy system fueling the rider during the long bicycle race.