Clubs increasingly like to control every aspect of their players' fitness, testing them weekly, providing individual exercise plans and dictating diet. Sometimes, however, outside influences come into play.
For the increasing number of Muslims in the Premier and Football League, normal eating habits are currently suspended, for this is the month of Ramadan.
During Ramadan, which runs from 1 to 29 August this year, devotees are expected to refrain from taking in food or liquid, smoking and sex, from before sunrise until sundown. This is intended to teach patience, spirituality, humility and submissiveness to Allah. It is one of the five pillars of Islam, the others being a declaration of faith, giving to charity, praying the five daily prayers and the Haj pilgrimage to Mecca.
Managers and coaches may question the wisdom of a footballer having to train and play when fasting, but this is something that Muslims know is part of their life.
Some, like the former Tottenham and West Ham striker, Frédéric Kanouté, are strict observers. Kanouté, now at Seville, has been a practising Muslim since the age of 20. His faith, insists Kanouté, has never presented itself as a problem in his relationship with the coaching staff, team-mates or fans. But when it comes to Ramadan, they pepper him with questions.
"They're quite curious, yes. They wonder why I don't eat and ask all these questions, but you have to answer them. It's good also because it's witnessing the religion and we can talk about that. They see me praying in the dressing room, I don't think of how people look at me, I'm just natural and it's my way.
"Islam has helped me to be this way, so this is normal. It's a path you take to keep you calm, to help you think about the place you live in, to love your neighbour. It's strange when I hear about all these problems of terrorism because it's the opposite of what I understood for Islam."
In a diverse Premier League, an increasing number of players are followers of Islam. You'll see them cup their hands in silent prayer before kick-off, then brush them over their face. Kolo and Yaya Touré, Nicolas Anelka and Samir Nasri are all talented players who would not want any fuss over their faith, but during the month of Ramadan, games can become even more of a challenge than usual.
In 2009, after only half an hour of Inter's 1-1 draw with Bari, the fasting Sulley Muntari was substituted, with manager Jose Mourinho stating that Ramadan had "not arrived at the ideal moment for a player to play a football match". His comments drew widespread criticism, which Mourinho later clarified by saying: "Muntari's decision is not to be criticised because it is a question of faith and religion. That means that I accept it. I never said Muntari should forget his religion and practice."
Some players compromise. Anelka has said that he initially fasted in daylight hours as prescribed, but "I realised I often got injured just after the period of Ramadan, so I don't observe it strictly any more".
A similar approach is followed by Arsenal striker Marouane Chamakh. "I have no problem fasting during Ramadan, it becomes normal. The day before a game and on match days I do not fast, but I'll make up the lost days later."
Ipswich striker Nathan Ellington converted to Islam seven years ago, and has just set up the Association of Muslim Footballers, whose purpose is to inform non-believers. He said educating the footballing authorities will help alleviate the type of comments that Mourinho came out with, which he described as "unfair".
Ellington added: "When I'm playing, I won't fast, but I'll make up for the missed day afterwards. For training, there's not a problem either, as you can get your hydration and nutrients with the suhoor [the early pre-dawn breakfast] which then helps. The only difference is afterwards when the rest of the players go off [to eat] and you have to hang on for a while longer, until the iftar meal at sunset."
The Millwall winger Hameur Bouazza admitted fasting can be problematic, but said it was part of his faith. "I'm proud to be a Muslim. I'm not going to say [combining fasting and football] is easy. Ramadan is hard, and I try to do my best every time. You know God is there to help us, we believe in him and he believes in us as well. We just need to pray and believe in him."
The issue of fasting and playing is a tricky one with the religious needs of the player somewhat at odds with the footballing needs of his manager and the club. Until now, there have not been any defining guidelines on the issue, but as more Muslim players find a place in the top leagues of Europe the issue of fasting during the holy month – which arrives annually 10 days earlier than the previous year – will not be going away.
Premier League Muslims
Marouane Chamakh, Abou Diaby, Samir Nasri (left), Bacary Sagna, Armand Traoré Arsenal
Habib Beye Aston Villa Nicolas Anelka Chelsea
Marouane Fellaini Everton
Hatem Ben Arfa, Cheick Tioté Newcastle
Edin Dzeko, Kolo Touré, Yaya Touré Manchester City
Adel Taarabt Queen's Park Rangers
Ahmed Elmohamady Sunderland
Younes Kaboul Tottenham
Youssuf Mulumbu West Bromwich
Ali Al Habsi, Mohamed Diame Wigan