Increasing emphasis is being placed on the physical performance and preparation of Premiership players, wsith most clubs utilising the expertise of physiologists and sport scientists in order to gain a winning edge. This has led to an increase in published physiological research on association football. The methods used to monitor player performance include hand notation, tape recorded commentary, cine film analysis, computer-aided analysis and a combination of all of these techniques. Although there are issues relating to the reliability and validity of these data collection methods, the findings have produced fairly standard data related to the physiological requirements of the game (Tumilty 1993).
Shephard (1999) summarised the research findings related to work rate in elite male players as that, covering a distance of 8 - 12 km per match, the aerobic energy system was utilised for the majority of activities (walking, jogging and sub maximal running), but this was interspersed with short burts of high intensity work which relied on anaerobic energy systems. During a match a player typically receives and makes about 30 passes.
Drust et al (1998) showed the following percentages of total work:
The intermittent nature of the game has been shown to increase the energy requirement, as have the activities of stopping, turning, jumping and tackling (Reilly 1997). Research by Bangsbo (1994) showed that differences in player positions, and therefore in on-field tasks, have an effect on the physiological requirements of players. Midfield players cover the greatest distance and require an aerobic profile, with an ability to sustain effort at close to their aerobic threshold (the maximum intensity before work becomes anaerobic).
Shephard (1999) observed a heart rate range of between 155 - 170 bpm during play. However, the value of heart rate as an indicator of exercise intensity may be inflated in the competitive environment by emotional stress, intermittent exercise, isometric contractions and thermal stress (Tumilty 1993). Bangsbo (1994) reports that although heart rate correlates well with maximal oxygen uptake during steady state work, it may not be totally accurate during intermittent exercise.
Bangsbo (1994) observed average oxygen consumption of around 70% of maximal oxygen consumption during matchplay. However, Ogushi et al (1993) reports practical problems (playing association football with a large 'Douglas bag' that collects exhaled air) which make it difficult to measure oxygen consumption during competition. Furthermore, these findings have poor external validity. Research by Apor (1988) using a cycle ergometer showed maximal oxygen uptake values of 60 - 70 millilitres per kilogram per minute in elite players, but this method may underestimate a player's potential on field performance because of its intermittent nature.