During relaxed breathing, which muscles are primarily relaxed during exhalation?

During relaxed breathing, particularly during exhalation, the primary muscles that function are related to the natural process of expiration. The diaphragm is typically the most pivotal muscle in inspiration, but during relaxed breathing, the focus shifts to passive forces to aid in exhalation.

In this context, the external intercostal muscles are primarily involved in inhalation, helping to expand the thoracic cavity. They contract during this phase but not during relaxed exhalation, where their role diminishes.

The internal intercostal muscles do engage during forced exhalation, contributing to a more forceful air expulsion from the lungs by actively pulling the ribs downward and inward. However, this is not the case in relaxed breathing, where exhalation is largely passive and does not heavily rely on the internal intercostals.

The abdominal muscles, while they may assist in forced exhalation, are primarily relaxed during normal, quiet breathing. Their relaxation allows for the natural recoil of the lungs and thoracic cavity.

Thus, the correct understanding highlights that during relaxed breathing, especially during passive exhalation, the external intercostal muscles are not the main contributors. The emphasis lies in the passive nature of breathing mechanics, with structures simply allowing air to flow out rather