Why does a larger portion of each breath reach the alveoli during exercise?

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Medical illustration of the human chest showing the lungs, diaphragm, ribs, trachea, bronchus, and bronchioles, with one lung cut away to reveal internal structures. — human respiratory system The lungs serve as the gas-exchanging organ for the process of respiration.

During exercise, a larger portion of each breath reaches the alveoli because the volume of inspired breaths increases significantly.1

In the human respiratory system, not all inspired air participates in gas exchange because a portion remains in the conducting airways, which do not facilitate gas exchange. This volume is known as dead space. At rest, this portion accounts for approximately one-third of each breath. However, as the size of inspired breaths increases during physical activity, the proportion of air that remains in the conducting airways decreases to as little as 10 percent, allowing a greater percentage of the total inspired air to reach the alveoli where gas exchange occurs.12