2.Aerobic (cardiorespiratory) endurance is the highest proportion of VO2max at which an individual can sustain >20 minutes' activity. It is closely allied to the lactate thresholds described in standard exercise physiology texts, the point at which muscular fatigue begins to be hastened. Elite endurance athletes can sustain activity typically at greater than 80% of their aerobic power, whereas sedentary or diseased individuals may only be able to sustain activity at 40-50% of aerobic power What this means is that the inactive or diseased person not only has a reduced capacity but also cannot utilize as much of whatever capacity they possess compared with the more active or fitter individual.