Nutrition advice for Football Players
While the average distance covered by a top-class outfield player during a 90-minute match is over 10,000m, at an average speed of over 7km per hour, these figures do not accurately represent the full demands placed on a player. In addition to running, a player must jump, change direction, tackle, accelerate and decelerate, etc., and each of these individual tasks requires an energy input over and above that required simply to cover a similar distance at a constant speed. Scientific investigation has shown that the true demands on a player can be approximated at roughly 70% VO2 max. This is based on evidence of heart rate, sweat loss, increase in body temperature, and depletion of carbohydrate stores within the muscles (intramuscular glycogen).
The specific demands of the different positions within a team are not as clearly defined as in some other team sports, such as rugby union. The obvious exception to this is, of course, the goalkeeper. A keeper relies little on the aerobic system for energy production since all the important phases of play for him last a relatively short time. The key performance quality of the keeper is probably agility, and this can be broken down further to include speed, power, strength and flexibility. If he happens to be tall, it's clearly an added bonus!
Popular training programs for keepers include repetitions of short sprints performed at maximal speed, with many changes of direction involved. Obviously, an element of skill can be built into this training by having to save a bombardment of shots at goal. This way, another important constituent of training is then automatically introduced, namely, the ability to regain one's feet in order to save a follow-up shot at goal.
However, to gain the edge in physical development, the keeper should also train away from the pitch so that upper and lower body strength and power can be improved in the weights room. In addition, plyometric training lends itself perfectly to improving the qualities necessary for agility around the goalmouth. Plyometric training does need to be conducted correctly, which includes the provision of generous rest periods between sets of exercises, but if done so can produce some significant improvements in the ability to move one's own body weight at speed.
As far as the rest of a soccer team goes, the differing demands are less obvious. However, a systematic analysis of soccer matches on video has shown that midfield players tend to cover the most distance, and other studies have - not surprisingly - shown these players to have the highest VO2 max scores, and to show the least fatigue when performing many repeated sprints in succession. Compared to forwards and defenders, midfield players tend to have a more continuous involvement in the game. However, while forwards and defenders usually have more time to recover between sprints, they also need to perform those sprints at a faster speed to be successful in their crucial phases of play.
Implications for training should become apparent. Clearly, the midfield players need more of an all-round fitness profile, with an emphasis on both aerobic and anaerobic capacity. Aerobic capacity relates to sustained performance (20-40 minutes), or performance during lengthy repetitions, each of 2-3 minutes in duration. Anaerobic capacity can be related to performance of a repeated nature, but with work/rest intervals of equal length, and not over 30 seconds.
The players regularly involved in attacking/ defending situations will need more training emphasis on speed. Speed training can itself be broken down into at least two phases - an acceleration component and a maximal speed component. For improvements in acceleration, repeated sprints of not less than six seconds in duration, performed from a standing or walking start, will be useful in training. This will help develop the neuromuscular function of the athletes. For development of maximal speed, a gentle increase in speed to about 85 per cent followed by a sustained burst at maximum speed for about six seconds will produce improvements that are more specific. This will help develop both the metabolic and neuromuscular qualities of the muscles involved. Put simply, to improve acceleration, accelerate as fast as possible in training. To improve maximal speed, the length of time spent running at current maximal speed during training should be increased. A relatively gentle acceleration phase before a sustained burst can best achieve this.
If the coach can accomplish these sorts of training goals by using drills that involve ball skills, then the players will become used to performing the skills under conditions of fatigue. As many will appreciate, it is under conditions of fatigue and mental pressure such as a competitive match that skills often become lost - unless they are both well-drilled for their own sake and practiced under simulated conditions of fatigue.
Moving away from training methods for a moment but continuing the analysis of the physical demands of the game, there is an interesting form of player behaviour that playing experience seems to encourage. Many players will recognise a phenomenon as common without perhaps understanding why. The behaviour in question is the avoidance of prolonged high-intensity activity that would require a corresponding long period of recovery - which can rarely be afforded in a competitive situation.
For instance, if a defender is involved in high-intensity activity as he assists in an attacking phase of play, he often will not attempt to return to his defending position in time for the immediate counter-attack. While this might be perceived as laziness, it may benefit both the individual player and the team in the longer term, providing the rest of the team has sufficient cover to deal with the counter-attack.
Sound physiological reasoning provides the basis for this. It has been shown that short periods of intense exercise (e.g. less than 15 seconds), when interspersed with rest periods of similar duration, produce a fairly low build-up of lactic acid in the muscles (a strong indicator of fatigue) even when this activity pattern is continued for some time. However, periods of intense exercise of about 30 seconds or more, even when accompanied by equal rest periods of 30 seconds (such that the work:rest ratio is till 1:1 as in the previous example), produce a far higher concentration of lactic acid in the muscles and also greater fatigue.
This situation is exactly what the experienced player is trying to avoid when he decides to return more slowly to his main position on the pitch. However, this obviously requires a large degree of teamwork, with team-mates prepared to cover for the defender concerned. If a team can achieve this sort of cooperation, it helps reduce player fatigue and increases performance capacity throughout the match as a whole. Clearly the role of the coach is paramount in organising this sort of team approach in spreading the workload, especially with inexperienced players. Indeed, some younger players may be almost too enthusiastic for the good of their own and the team's subsequent performance.
As already mentioned, the physical demands of the game are sufficiently high to require a high rate of energy production. Whatever the sport, this can only be done by the breakdown of carbohydrates, and soccer is no exception. This means that players should pay particular attention to this aspect of their diet - more especially when considering the notorious practices of soccer players when they are given no guidance about what to eat. The heavy training/match schedule that the British game involves only serves to increase the need for carbohydrate intake.
When discussing this subject, it is usual to express the form of the energy consumed as percentages (proportions) eaten as carbohydrate, fat and protein. While the typical diet for the general British population is about 40% carbohydrate, 45% fat and 15% protein, the recommended dietary proportions for a soccer player would be roughly 65% carbohydrate, 20% fat and 15% protein. However, the typical diet of the soccer player is actually very similar to that of the general population - too little carbohydrate and too much fat.
The work carried out some years ago by Jacobs and colleagues ("Muscle glycogen and diet in elite soccer players", European Journal of Applied Physiology, 1982, vol. 48, pp297-302) illustrates the potential pitfalls of a low-carbohydrate diet. These researchers studied players in the Malmo soccer team in Sweden -the side had finished as runners-up in the European Cup the previous season. The players consumed just 47 per cent of dietary energy as carbohydrates - well below the recommended values. Muscle glycogen stores were assessed immediately after a national league match (Day 1), and again 24 hours later after no training (Day 2), and 48 hours after the match after a very light training session (Day 3).
Muscle glycogen stores of the general population are approximately 70-90 mmol.kg-1 wet weight. The average values for the Malmo team were 46,69 and 73 mmol.kg-1 wet weight on the three days.
There is no reason why the players could not have refilled their muscle glycogen stores to pre-match levels within 24 hours if they had consumed a high-carbohydrate diet. Experiments have shown that, for highly trained athletes, a muscle glycogen level of well over 100 mmol.kg-1 wet weight is quite possible to achieve following two or three days of light training. The reason the soccer players didn't reach this sort of level was undoubtedly due to the lack of carbohydrate in their diet.
The importance of high muscle glycogen stores for performance in events lasting longer than 60 minutes has been demonstrated by numerous researchers. Specifically in relation to soccer, the diets (and hence the muscle glycogen stores) of players involved in an exhibition match have been manipulated, with those players having higher muscle glycogen stores before the match also covering a greater distance at a faster pace during the match. This effect was particularly noticeable towards the end of the match when glycogen always becomes lowered - and many goals are often scored as the game tends to open up. Therefore, a high-carbohydrate diet leads to increased muscle glycogen stores, which in turn leads to a greater distance covered during the final stages of the match, which in turn leads to your team scoring the winning goal in injury time! Well, not always, maybe, but you can increase the chances of it happening by taking a close look at players' diets
The information on this page is adapted from Williams (1996) with the kind permission of Electric Word plc.
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