Final answer:
The diaphragm moves significantly with each breath, typically enough to adjust lung volume by several hundred milliliters during normal respiration.
Step-by-step explanation:
Respiration moves the diaphragm significantly during breathing. The diaphragm is a sheet-like muscle that, when contracted during inhalation, moves downward and increases chest volume, which in turn reduces air pressure inside the lungs compared to outside, causing air to rush in. This can vary slightly depending on whether the breathing is shallow (costal breathing) or deep (diaphragmatic breathing).
A typical inhalation will change the lung volume by about 500 mL for a normal breath. When discussing forced breathing, such as during exercise or activities requiring active manipulation of breathing like singing, both inspiration and expiration are the result of muscle contractions, including those of accessory muscles, and can involve a greater volume change in the lungs.
During exhalation, relaxation of the diaphragm and intercostal muscles leads to an increase in air pressure inside the lungs compared to outside, and air flows out. The exact amount of movement of the diaphragm can vary with the depth of breath, but with each breath, it typically moves enough to adjust the lung volume by several hundred milliliters.