A yoga teacher is demonstrating the technique of breathing exericse during forced expiration the actively contracting muscles in his body include

Options

A. diaphragm
B. sternocleidomastoid
C. abdominal muscles
D. external intercostals

Answer

### Step-by-Step Solution:

1. **Understanding Expiration**: Expiration is the process of breathing out, where the volume of the thoracic cavity decreases, leading to an increase in pressure inside the lungs. This pressure difference allows air to flow out from the lungs to the atmosphere.

2. **Muscles Involved in Normal Expiration**: During normal expiration, the primary muscles involved are the internal intercostal muscles, which contract to help decrease the volume of the thoracic cavity. The diaphragm, which is a dome-shaped muscle, relaxes during this process.

3. **Forced Expiration**: In forced expiration, more forceful exhalation is required. This involves additional muscle groups beyond the internal intercostals.

4. **Role of Abdominal Muscles**: During forced expiration, the abdominal muscles contract. This contraction helps push the diaphragm upwards, further reducing the volume of the thoracic cavity and increasing the pressure inside the lungs, facilitating a more forceful exhalation.

5. **Conclusion**: Therefore, during forced expiration, the actively contracting muscles include the internal intercostal muscles and the abdominal muscles. However, since the question specifically asks for the actively contracting muscles in the body during forced expiration, the correct answer is the abdominal muscles.

### Final Answer:
The actively contracting muscles during forced expiration include the **abdominal muscles**.

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