Muscles get fatigued due to accumulation of

Options

A. adenosine triphosphate
B. `CO_(2)`
C. lactic acid
D. phosphate molecules

Answer

**Step-by-Step Solution:**

1. **Understanding Muscle Fatigue**: Muscle fatigue occurs during prolonged physical activity when the muscles are unable to maintain their performance.

2. **Role of Respiration**: During exercise, muscles require energy, which is derived from glucose through a process called respiration. This process can be aerobic (with oxygen) or anaerobic (without oxygen).

3. **Aerobic vs. Anaerobic Respiration**:
- **Aerobic Respiration**: Requires oxygen and produces carbon dioxide, water, and a significant amount of ATP (energy).
- **Anaerobic Respiration**: Occurs when oxygen levels are low, such as during intense exercise. This leads to the breakdown of glucose into lactic acid instead of carbon dioxide and water.

4. **Formation of Lactic Acid**: In anaerobic conditions, glucose (C6H12O6) is converted into lactic acid (C3H6O3). This process generates some ATP, but less than aerobic respiration.

5. **Accumulation of Lactic Acid**: As exercise continues and oxygen is scarce, lactic acid accumulates in the muscles. This accumulation is what leads to muscle fatigue and discomfort.

6. **Conclusion**: The correct answer to the question is that muscles get fatigued due to the accumulation of lactic acid.

**Final Answer**: Muscles get fatigued due to the accumulation of **lactic acid**.

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