What muscles allow for a greater than usual exhalation during expiration?

The internal intercostal muscles play a crucial role in facilitating a greater than usual exhalation during expiration, particularly during activities that require forceful breathing, such as exercise or during heavy exertion. These muscles are located between the ribs and assist in depressing the rib cage, which decreases the volume of the thoracic cavity and helps push air out of the lungs more forcefully.

During normal breathing, expiration is generally a passive process, but when the body demands more significant airflow, the internal intercostals actively contract to aid in this process. By drawing the ribcage down and inward, they enhance the pressure gradient necessary for effective exhalation beyond what is typically achieved with passive relaxation of the external intercostal muscles.

The other muscle options listed do not primarily serve this specific function for forced exhalation. The external intercostal muscles mainly assist with inhalation by elevating the ribs, while the transversus abdominis plays a role in stabilizing the trunk and does not directly contribute to the mechanics of breathing. The serratus anterior is mainly involved in the movement of the scapula and does not influence the expansion or contraction of the thoracic cavity during respiration.