The major movement produced during quiet breathing is accomplished by which muscle?

The diaphragm is the primary muscle responsible for the major movement during quiet breathing, also known as resting or tidal breathing. When the diaphragm contracts, it flattens and moves downward, increasing the volume of the thoracic cavity. This expansion creates a negative pressure within the chest, allowing air to be drawn into the lungs.

During quiet breathing, the diaphragm is the dominant muscle used, as it can efficiently generate the necessary changes in lung volume with minimal effort. Other muscles, such as the intercostal muscles, assist in breathing but play a more significant role during forced or vigorous breathing rather than during the quiet state. The rectus abdominis and external obliques are primarily involved in forced expiration and not in the process of inhalation occurring during quiet breathing.

Understanding the role of the diaphragm highlights its importance in respiratory physiology and explains why it is the central player in the mechanics of breathing at rest.