How is cardiorespiratory fitness measured well?

V02 Max. "...Vo2 max. Or maximum oxygen uptake, is considered the gold standard of cardiovascular, pulmonary, and muscle cell fitness. It is usually standardized per body weight and expressed in milliliters of oxygen per kilogram of body weight per minute, and is the maximum amount of oxygen your body (basically your muscles) can utilize." http://www.Cptips.Com/exphys.Htm.