During a long-distance race, which sequence best describes how the body provides energy to muscles as the race progresses?

• A. Initially uses stored ATP and creatine phosphate, then switches to anaerobic glycolysis, and finally relies primarily on aerobic respiration.
• B. Depends exclusively on the breakdown of proteins for energy during the race.
• C. Uses only stored ATP for the entire duration of the race.
• D. Relies solely on anaerobic glycolysis throughout the entire race.

Answer: (A)

Verified step by step guidance

1. Understand the energy systems in the human body: The body uses different methods to produce energy depending on the duration and intensity of physical activity. These include stored ATP, creatine phosphate, anaerobic glycolysis, and aerobic respiration.
2. Step 1: Stored ATP and creatine phosphate are used initially. ATP is the primary energy currency of the cell, and creatine phosphate acts as a quick reserve to regenerate ATP during short bursts of activity. This system is used for the first few seconds of the race.
3. Step 2: As the race progresses and the initial ATP and creatine phosphate stores are depleted, the body switches to anaerobic glycolysis. This process breaks down glucose into pyruvate, producing ATP without requiring oxygen. However, it also generates lactic acid, which can lead to muscle fatigue.
4. Step 3: For longer-duration activities like a long-distance race, the body primarily relies on aerobic respiration. This process uses oxygen to completely break down glucose, fatty acids, and sometimes amino acids into carbon dioxide and water, producing a large amount of ATP. Aerobic respiration is more efficient and sustainable for prolonged activity.
5. Step 4: Clarify misconceptions: The body does not rely exclusively on protein breakdown for energy during a race, nor does it use only stored ATP or solely anaerobic glycolysis for the entire duration. Energy systems shift dynamically based on the demands of the activity.