From the Guidelines
The abdominal muscles contribute to forced expiration by pressing into the abdominopelvic viscera which moves the thoracic diaphragm superiorly, and reduces thoracic volume. This is because during forced expiration, the abdominal muscles (rectus abdominis, external and internal obliques, and transversus abdominis) contract, increasing intra-abdominal pressure, as described in general medical knowledge. The other statements contain inaccuracies:
- upper limb muscles are most effective when the arms are fixed (not free to move)
- the sternocleidomastoid attaches to the sternum and clavicle (not upper ribs), and is used in inspiration by elevating the sternum, as seen in patients with respiratory distress 1
- the scalenes are innervated by cervical spinal nerves (not the phrenic nerve), though they do assist with inspiration by elevating the first two ribs, as described in the context of accessory muscles of respiration 1. In the context of respiratory disease, such as pneumonia or COPD, the use of accessory muscles of respiration can be critical in maintaining adequate ventilation, as seen in studies on pulmonary rehabilitation 1.
From the Research
Accessory Muscles of Respiration
- The provided studies do not directly address the question regarding accessory muscles of respiration 2, 3, 4, 5, 6.
- However, based on general knowledge of anatomy and physiology, it is known that:
- The abdominal muscles contribute to forced expiration by pressing into the abdominopelvic viscera, which moves the thoracic diaphragm superiorly and reduces thoracic volume.
- The sternocleidomastoid muscle can assist in inspiration by elevating the ribs.
- The scalenes are also involved in assisting inspiration, but they are innervated by the spinal nerves (C3-C5), not the phrenic nerve.
- The statement that "The abdominal muscles contribute to forced expiration by pressing into the abdominopelvic viscera which moves the thoracic diaphragm superiorly, and reduces thoracic volume" is correct based on anatomical and physiological principles, although it is not directly supported by the provided studies 2, 3, 4, 5, 6.