Field sports such as football, team handball, hockey, rugby union and rugby league, Australian & Gaelic Rules football are characterised by a typically stop-start nature, with varying movement speeds, multiple changes of direction and the execution of decisions and individual skills under conditions of game pressure and/or fatigue. The nature of the movements in these sports requires the utilisation, and therefore training, of all three energy systems (ATP-PC, Glycolitic/Lactic acid and Aerobic systems). Despite the often stop-start nature of these sports, which heralds an increase in anaerobic energy contributions, high-intensity aerobic power and conditioning can be critical for success in many field sports.