Inspiratory reserve volume (IRV) is the maximum amount of air that can be inhaled after a normal inhalation. It represents the extra air that the lungs can hold beyond the typical breath. This volume is important for assessing lung function and respiratory health. IRV is measured during pulmonary function tests and is a key component of lung capacity calculations. It helps determine how well the lungs can expand and contract, which is essential for activities that require increased oxygen intake, such as exercise or physical exertion.