What role do the scalenes play during respiration?

The scalenes are primarily recognized as accessory muscles of breathing. During respiration, especially when the demand for oxygen increases—such as during vigorous exercise—the scalenes assist the primary respiratory muscles, primarily the diaphragm and intercostal muscles. Their elevation of the first two ribs and stabilization of the cervical spine helps to expand the thoracic cavity, facilitating greater airflow into the lungs.

While various muscles are involved in different aspects of respiratory mechanics, the scalenes are specifically recruited in situations that require deeper or more forceful breaths rather than in the regular, quiet breathing process, where the diaphragm predominantly operates. Their primary function in respiration increases the lung's capacity to intake air without being the main drivers of everyday breathing or expiration.