Because of the game duration, soccer is mainly dependent upon aerobic metabolism. Distances covered at top level are in order of 10~12km for the field players, and about 4km for the goalkeeper. The average work intensity measured as percentage of maximal heart rate during a 90 minute soccer match is close to the anaerobic threshold; the highest exercise intensity where the production and removal of lactate is equal; normally between 80~90% of HRmax in soccer players. Although aerobic metabolism dominates the energy delivery during a soccer game, the most decisive actions are covered by means of anaerobic metabolism. To perform short sprints, jumps, tackles, and dual play, anaerobic energy release is determinant with regard to who is sprinting fastest or jumping highest. This is often crucial for the match outcome. It would be physiologically impossible to keep a higher average intensity over a longer period of time due to the resultant accumulation of blood lactate. Therefore, the players need periods of low-intensity activity to remove lactate from the working muscles. Previous studies indicated that, no one has yet managed to provide accurate data when measuring oxygen uptake. However, establishing the relation ship between heart rate and VO2 during a game allows accurate indirect measurement of VO2 during soccer matches. Furthermore, researchers indicated that a 5% improvement in running economy could increase match distance by approximately 1000 m. Strength and power are equally as important as endurance in soccer. By increasing the available force of muscular contraction in appropriate muscle groups, acceleration and speed may improve in skills critical to soccer such as turning, sprinting and changing pace. High levels of maximal strength in upper and lower limbs may also prevent injury in soccer.