State any two characteristics of muscle fatigue. How is it caused?

Explanation

### Step-by-Step Text Solution:

1. **Definition of Muscle Fatigue**:
Muscle fatigue refers to a temporary decrease in the ability of a muscle to generate force. It occurs after prolonged physical activity.

2. **Characteristic 1**:
One characteristic of muscle fatigue is that the muscle fibers stop responding effectively to stimulation. This means that even when the nerve sends signals to the muscle, the muscle does not contract as strongly or at all.

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