Which chemical causes the muscle fatigue?

Explanation

**Step-by-Step Solution:**

1. **Understanding Muscle Fatigue:**
- Muscle fatigue is defined as the decrease in power production in response to contractile activity. This means that after prolonged or intense exercise, muscles can become less effective at generating force.

2. **Identifying the Chemical Involved:**
- The primary chemical responsible for muscle fatigue is lactic acid.

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