Which of the following will contribute to fatigue of the aerobic energy system? (A) An increase of blood glucose and muscle glycogen (B) An increase in lactic acid and creatine phosphate (C) A decrease in lactic acid and creatine phosphate (D) A decrease of blood glucose and muscle glycogen - HSC - SSCE Personal Development and Physical Education - Question 13 - 2011 - Paper 1

To analyze the options, we must consider how fuel sources impact the aerobic energy system's ability to sustain exercise. The aerobic system primarily relies on carbohydrates and fats as its energy sources.

1. Increase of Blood Glucose and Muscle Glycogen (Option A): This scenario would likely improve performance rather than contribute to fatigue, making this option unlikely.

2. Increase in Lactic Acid and Creatine Phosphate (Option B): While lactic acid can contribute to fatigue in anaerobic conditions, it doesn't typically affect the aerobic system directly due to its reliance on steady-state energy provision.

3. Decrease in Lactic Acid and Creatine Phosphate (Option C): A decrease in these would not contribute to fatigue but rather suggest an efficient energy system at work.

4. Decrease of Blood Glucose and Muscle Glycogen (Option D): This scenario critically undermines the energy supply for the aerobic system, leading to fatigue.

Therefore, the most logical choice that contributes to fatigue in the aerobic energy system is Option D: 'A decrease of blood glucose and muscle glycogen.'