So cardiorespiratory fitness (CRF) includes cardiovascular fitness and thus refers to the health of the heart, lungs, and circulatory system in delivering oxygen to the body’s tissues during sustained physical activity. CRF reflects the integrated ability to transport oxygen from the atmosphere to the mitochondria to perform physical work. It quantifies the functional capacity of an individual and is dependent on a linked chain of complex processes that include lung function and diffusion of oxygen into the blood vessels.
