Energy

Energy

Just to remind you, there are three major systems available for the production of energy in the muscles: the ATP-PC system for high-intensity short bursts; the anaerobic glycolysis system for intermediate bursts of relatively high intensity (this system produces the by-products of lactate ions and hydrogen ions, commonly known as lactic acid); and finally, there is the aerobic system for long efforts of low to moderate intensity (www.soccerperformance.org).

With sporting events such as cycling, swimming and running, where the intensity is constant for the duration of the event, it is possible to estimate the relative contribution of each energy system. For example, the energy for the 100m sprint is split 50 per cent from the ATP-PC system and 50 per cent from the anaerobic glycolysis system, whereas the marathon relies entirely on the aerobic system (www.pponline.co.uk). By contrast, games such as football are characterized by variations in intensity. Short sprints are interspersed with periods of jogging, walking, moderate-paced running and standing still. This kind of activity has been termed 'maximal intermittent exercise' (www.brianmac.co.uk).

It would seem reasonable to assume that during a football game all three energy systems would be required, as intensity varies from low to very high. However, because it is not obvious just how fast, how many and how long the sprints are, and just how easy and how long the intervening periods are, it is difficult to determine which of the energy systems are most important. Thus most of the football-related research has attempted to tackle this problem (Ozawa, 2006).

A 15m sprint every 90 seconds

English researchers Reilly and Thomas (1976) investigated the patterns of football play in the old first division. They found that a player would change activity every 5-6 secs, and on average he would sprint for 15m every 90 seconds. They found the total distance covered varied from 8 to 11 km for an outfield player - 25 per cent of the distance was covered walking, 37 per cent jogging, 20 per cent running below top speed, 11 per cent sprinting and 7 per cent running backwards (Tim, Hogan, Chang, 2006). (Ozawa, 2006), researching football in Japan, confirmed these findings, showing 70 per cent of the distance was covered at low to moderate pace below 4 m/s, with the remaining 30 per cent covered by running or sprinting at above 4 m/s. Thus, for example, if a football player covers 10 km in total, around 3 km will be done at fast pace, of which probably around 1 km will be done at top speed (www.brianmac.co.uk).

The pattern of football play has also been expressed in terms of time. Hungarian researcher Peter Apor and the Japanese researchers both describe football as comprising sprints of 3-5 secs interspersed with rest periods of jogging and walking of 30-90 secs. Therefore, the high to low intensity activity ratio is between 1:10 to 1:20 with respect to time. The aerobic system will be contributing most when the players' activity is low to moderate, i.e. when they are walking, jogging and running ...