Long distance, competitve runners are usually small and wiry and run more slowly than sprinters, who run much shorter distances and generally have a loarger bulk of nuscles. Which of the following best explains the differences between the two types of runners?

Options

A. Long distance runners run more slowly because lactic acid quickly builds up in muscels and causes fatigue. Sprinters increase the oxygen supply to each muscle, enough for lactic acid to build up in their muscles.
B. The large muscels of sprinters increase the oxygen supply to each muscle, preventing lactic acid from forming.
C. Sprinters do not run for long enough for sufficient lactic acid to build up in their muscles therefore they can have large muscles for more power. By being lighter and running more slowly long distance runners ensure that their muscles receive enough oxygen for aerobic respiration.
D. sprinters run faster because their large muscles have more blood running through them to stop anaerobic respiration from taking place. Long distance runners run more slowly because they are using the energy from anaerobic respiration, which does not produce as much ATP as aerobic respiration.

Answer

To explain the differences between long-distance competitive runners and sprinters, we can analyze the characteristics of their muscle fibers and how these relate to their performance.

### Step-by-Step Solution:

1. **Understanding Muscle Fiber Types**:
- There are two main types of skeletal muscle fibers: fast twitch fibers and slow twitch fibers.
- Fast twitch fibers are designed for quick, powerful bursts of activity but fatigue quickly. They are predominant in sprinters.
- Slow twitch fibers are more endurance-oriented, allowing for prolonged activity without fatigue. They are predominant in long-distance runners.

2. **Characteristics of Long-Distance Runners**:
- Long-distance runners are typically smaller and wiry, which helps reduce weight and improve efficiency over long distances.
- They primarily utilize slow twitch muscle fibers, which are better suited for endurance activities. This allows them to sustain activity over longer periods without quickly tiring.

3. **Characteristics of Sprinters**:
- Sprinters are generally bulkier and muscular, which provides the explosive power needed for short bursts of speed.
- They rely on fast twitch muscle fibers that enable them to perform high-intensity activities for short durations. This muscle type allows for rapid movements but leads to quicker fatigue.

4. **Performance Implications**:
- The difference in muscle fiber composition directly affects the performance of each type of runner. Sprinters can generate more power and speed due to their larger muscle mass and fast twitch fibers, while long-distance runners excel in endurance due to their lighter build and slow twitch fibers.

5. **Conclusion**:
- The differences in body composition and muscle fiber types explain why long-distance runners are generally smaller and slower compared to sprinters, who are bulkier and faster.

### Final Answer:
The differences between long-distance competitive runners and sprinters can best be explained by the type of muscle fibers they predominantly use: long-distance runners have more slow twitch fibers for endurance, while sprinters have more fast twitch fibers for speed and power.

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