The innermost intercostal muscle is a crucial part of the respiratory system, assisting in the process of inhaling and exhaling. It is a striated muscle that is located between the internal intercostal muscle and the innermost layer of the intercostal membrane. Synonyms for the innermost intercostal muscle include the deep intercostals or the intercostales intimi. This muscle is responsible for stabilizing the rib cage and is essential for the movement of the thoracic cage during breathing. Regular exercise of the innermost intercostal muscle can improve respiratory function and overall lung health.