The internal intercostal muscles contract during ..................

Explanation

### Step-by-Step Solution:

1. **Understanding Intercostal Muscles**:
- The human body has two types of intercostal muscles: external intercostal muscles and internal intercostal muscles.
- These muscles are located between the ribs and play a crucial role in the mechanics of breathing.

2. **Role of External Intercostal Muscles**:
- The external intercostal muscles are primarily involved in the process of inhalation (inspiration). They contract to elevate the ribs and expand the chest cavity, allowing air to flow into the lungs.
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