Soccer is a sport requiring high levels of physical fitness. It is one of those rare games which demands not only speed but agility, strength, power and endurance. Players at top levels can run over 14 km in a game whilst not forgetting the frequent accelerations, decelerations, changes of direction and jumps they must undertake.

Fitness is important at all levels of the game, whilst being essential for top level players, it is beneficial for beginners who will improve both their effectiveness and enjoyment through good standards of fitness. The aim of fitness training in football is to enable a player to cope with the physical demands of the game as well as allowing the efficient use of his various technical and tactical competencies throughout the match.

Fitness may be described as a set of attributes that an individual has or has acquired which help in their ability to perform physical activity. The diagram below (Fig 1) outlines the general components which make up and are required for physical fitness in sport. Mental fitness and diet could be included but the diagram refers to the main components of fitness which require physical activity and which bring about physiological changes in the body.

Fitness as mentioned earlier is based on the attributes an individual has, meaning what he is born with or has acquired, in other words through training. Thus, performance is influenced by inherited abilities (genetic) and training status. An individual who is "naturally gifted" will still need proper training to make the most of their talent.

Different sports require different fitness components. Football players must be able to perform prolonged intermittent exercise (endurance), exercise at high-intensity, sprint, and develop high levels of power (force) when kicking and tackling. Good levels of agility and coordination are also necessary and distinguish between elite and average players.

During a game the exercise intensity varies continually thus fitness training should be as realistic as possible. Training should also involve regular use of the ball as this will not only help develop the specific muscles involved in match play, but improve technical and tactical skills and help keep players interested. Coaches such as Marcello Lippi formerly at Juventus, are big believers in individual fitness programs as every player has different needs. This is important as well when training women and youth players.

Fig 2 details the major components involved in football specific training.

In all the different components of fitness mentioned above, there are certain basic principles that apply to football fitness training.

Frequency - Refers to the quantity of training sessions during a defined period of time, often a week. For example, a professional player may train twice a day, 5 times a week.

Intensity - Can be simply defined by how hard a player trains. Too much exercise can lead to injury and fatigue whereas too little will not have enough of an effect. Elite players can train longer and harder than players at a lower level. Intensity is often based on the number of repetitions and how many exercises/sets done. It is linked to the principle of progressive overload.

Progressive overload & duration - Training programs should stress the players’ physiological mechanisms enough to cause an improvement in the desired area. This means that working on the same fitness programme for a long time will not bring about improvement. Therefore, training status will only be bettered by gradually increasing the load that the body is working against. Incorrect overload may bring injury and demotivation due to over-zealous targets. The duration is the time spent in a training session and is dependent upon the sport and individual.

Type of exercise & Specificity - All training sessions and types of exercise undertaken need to be designed for the specific demands of the sport, the position being trained for and the individual needs of the athlete.

Reversibility - "Use it or lose it !" What is gained through training will eventually be reduced or lost if exercise is stopped or reduced. A sufficient level of general activity should be planned during periods of inactivity (Injuries - if possible, time away from home or during the summer break).

Recovery (detraining) - Needs to be carefully monitered. Too greater recovery periods will lead to the benefits being lost or too shorter recovery time can lead to overtraining again resulting in injury. Training provides the stimulus for increased performance but it is during the recovery when the bodies’ physiological mechanisms for improvement are implemented.

The performance potential of a football player can be improved by fitness training which is generally divided up into aerobic, anaerobic and specific muscle training. Other factors that are important to a players' progress are his genetic background, diet and mental fitness. Improvements in performance depend upon the training methods used. Frequency, intensity, progressive overload, type of exercise, & specificity and recovery all play a part in determining performance.