What is the contribution of the following in breathing?
Abdominal muscles

Explanation

### Step-by-Step Solution:

1. **Understanding the Structure**: The abdominal muscles play a significant role in the process of breathing. They are located below the diaphragm, which is a dome-shaped muscle that separates the thoracic cavity (where the lungs are located) from the abdominal cavity.

2. **Role in Forced Respiration**: The primary function of the abdominal muscles during breathing is to assist in forced respiration. This occurs when we need to exhale more air than normal, such as during vigorous exercise or when blowing out air forcefully.

3. **Mechanism of Action**: When the abdominal muscles contract, they push the contents of the abdomen upwards. This upward movement reduces the volume of the thoracic cavity (the chest area), which in turn increases the pressure in the chest.

...