Question

Which of the following correctly represents the sequence of energy systems used during a 400 m sprint race?

• A. Aerobic $\rightarrow$ ATP-PC $\rightarrow$ Lactic Acid
• B. ATP-PC $\rightarrow$ Lactic Acid $\rightarrow$ Aerobic
• C. Lactic Acid $\rightarrow$ ATP-PC $\rightarrow$ Aerobic
• D. Aerobic $\rightarrow$ Lactic Acid $\rightarrow$ ATP-PC

Hint:

Remember that all three energy pathways contribute to some degree at all times during exercise.
However, the dominant system changes based on the duration and intensity of the activity.
For short, explosive, high-intensity events, the sequence always begins with the rapid ATP-PC system.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
This question tests our understanding of human bioenergetics and the transition of energy pathways during exercise.
A 400 m sprint is a high-intensity, maximal-effort running event lasting approximately 43 to 60 seconds.
During this brief, intense performance, the human body transitions through various energy pathways to meet demands.

Step 2: Detailed Explanation:
1. When an athlete starts a 400 m sprint, the body requires immediate, explosive energy.
2. The primary source for this explosive start is the ATP-PC (Adenosine Triphosphate-Phosphocreatine) system.
3. This system operates anaerobically (without oxygen) and provides maximum energy for the first 8 to 10 seconds of sprinting.
4. As the phosphocreatine stores in muscles deplete rapidly, the body must transition to another energy pathway.
5. Around the 10-second mark, the Lactic Acid system (also called anaerobic glycolysis) becomes the dominant pathway.
6. This system breaks down stored glycogen to produce ATP, generating lactic acid as a metabolic byproduct.
7. The Lactic Acid system supplies energy for high-intensity work lasting up to 60 to 90 seconds.
8. As the runner nears the end of the race and transitions to recovery, the Aerobic system increases its contribution.
9. Although slow to respond, the Aerobic system utilizes oxygen to help clear lactate and restore metabolic balance.
10. Therefore, the sequence of metabolic system dominance is ATP-PC, followed by Lactic Acid, and then Aerobic.

Step 3: Final Answer:
This progression of metabolic pathways corresponds to Option (B).