After physical exercise we sometimes get muscle cramps. This results due to

Options

A. conversion of pyruvate to alcohol
B. non-conversion of glucose to pyruvate
C. non-conversion of glucose to lactic acid
D. conversion of pyruvate to lactic acid

Explanation

**Step-by-Step Solution:**

1. **Understanding Muscle Cramps**: Muscle cramps often occur after intense physical exercise. They can be painful and are a common experience for many individuals who engage in strenuous activity.

2. **Identifying the Cause**: The primary cause of muscle cramps during or after exercise is related to the metabolic processes that occur in muscle cells, particularly when oxygen levels are low.

3. **Anaerobic Respiration**: During heavy exercise, the demand for oxygen in the muscles exceeds the supply. As a result, the body resorts to anaerobic respiration, which does not require oxygen.

4. **Conversion of Pyruvates**: In anaerobic conditions, glucose is broken down to pyruvate through glycolysis. However, due to the lack of oxygen, the pyruvate cannot be fully oxidized through aerobic respiration.

5. **Formation of Lactic Acid**: Instead, the pyruvate is converted into lactic acid. This accumulation of lactic acid in the muscles is what leads to muscle cramps and fatigue.

6. **Conclusion**: Therefore, the correct answer to the question is **D. Conversion of pyruvates to lactic acid**. This process is responsible for the muscle cramps experienced after intense physical activity.

---