Name two energy sources for muscle contraction.

Explanation

**Step-by-Step Solution:**

1. **Identify the Question:** The question asks for two energy sources that are necessary for muscle contraction.

2. **First Energy Source - ATP:**
- ATP stands for adenosine triphosphate.
- It is the principal molecule for storing and transferring energy within cells.
- ATP is often referred to as the "energy currency" of the cell because it provides the energy required for various cellular processes, including muscle contraction.
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