A drop in the force of contraction after prolonged stimulation is known as muscle fatigue.

Explanation

**Step-by-Step Solution:**

1. **Understanding Muscle Fatigue**: Muscle fatigue refers to the decline in the ability of a muscle to generate force after prolonged stimulation. This means that when a muscle is used continuously without rest, its performance decreases over time.

2. **Identifying the Causes**: There are two primary causes of muscle fatigue:
- **Neural Fatigue**: This occurs due to limitations in the nerves that are responsible for sending signals to the muscles. When nerves are overstimulated, they may not be able to sustain the signals needed for muscle contraction.
- **Metabolic Fatigue**: This type of fatigue arises from the muscle fibers themselves. Even if the nerves are functioning properly, the muscle fibers may become less capable of contracting due to depletion of energy sources or accumulation of metabolic byproducts.

...