2018 Volume 15 Pages 85-92
Cardiorespiratory fitness (CRF) is defined as the ability of the circulatory and respiratory systems to supply oxygen during sustained physical activity and is usually expressed as maximal oxygen uptake (VO2max) during maximal exercise testing. There are five major determinants of VO2max: functions of the heart, lung, kidney, muscle, and blood (hemoglobin). Cardiac output, pulmonary diffusion capacity, oxygen-carrying capacity, renal function, and other peripheral limitations like muscle diffusion capacity, mitochondrial enzymes, and capillary density are all examples of VO2max determinants. VO2max, measured by cardiopulmonary exercise testing, provides what is probably the most sensitive assessment of the effect of new therapy on the function of any diseased organ system whose major function is to couple pulmonary gas exchange to cellular respiration. For example, it is important to determine whether new medical, surgical, and rehabilitative procedures can effectively intervene to improve the gas transport capability of a diseased organ system.