Soccer is characterised as a high intensity, intermittent non-continuous exercise. Players cover approximately 10 km of ground per game, of which 8 to 18% is at the highest individual speed. In higher levels of competition there is a greater number of tackles and headings plus a greater percentage of the game is performed at maximum speed. The average aerobic energy yield during a national level game is around 80% of the individual maximum. Blood lactate concentration during a game averages 7 to 8 mmol/L. Because of a high energy yield most players have empty muscle glycogen stores at the end of the game, were hypohydrated and also have an increased body temperature. Soccer players of national and international standard have a maximal aerobic power of around 60 to 65 ml/kg/min, an above average anaerobic alactacid power, and a greater buffer capacity and muscle strength compared with untrained controls, yet seem to be less flexible.