ABSTRACT
In sports events or strenuous exercise lasting more than 1 minute, the predominant mode of energy production is aerobic. This means that performance is limited by the oxygen that is delivered to and utilized by the active muscles. The level of performance is determined by the nature of training, which can affect both central and peripheral physiological factors. When the muscles are well trained, as in the case of elite endurance athletes, the limiting factors in determining the maximal oxygen uptake are the cardiac output and the oxygen-carrying capacity of the blood. The maximal cardiac output is also highly important when exercise is conducted in the heat since it then subserves two functions – the distribution of blood to the skin for thermoregulatory purposes and the supply of oxygen to the active muscles for energy metabolism.
