The capacity to continue prolonged physical activity and withstand fatigue. The level of aerobic endurance is reflected by the length of time an aerobic exercise involving large muscle groups (e.g. running, cycling, and swimming) can be performed. It depends on the ability of the lungs and heart to take in and transport adequate amounts of oxygen to working muscles, and on the ability of the muscles to extract and use the oxygen efficiently. Most sports scientists regard maximal oxygen uptake (VO2max) as the best objective laboratory indicator of aerobic endurance.