How do footballers maintain energy levels throughout a gruelling season? Sky Sports spoke to Nick Littlehales - an elite sports sleep coach who has worked with Cristiano Ronaldo, the Class of 92, Thierry Henry and more - to look at his influence on the way footballers recover and sleep.

Building on the initial work of British Cycling, Team Sky, with a hefty budget, helped transform not only the success of professional British cyclists, but the way cycling is viewed in the United Kingdom.

A crack team of sports scientists, strategists, data analysts and experts in every department from nutrition to performance all played their part. One man who played an important role in the success story is Nick Littlehales, an elite sleep coach who instructed Team Sky on how to best rest their weary riders. The results were incredible.

"People were looking at how they achieved their success," Littlehales tells Sky Sports. "And the likes of Dave Brailsford and Victoria Pendleton are saying 'well, we actually take notice of our sleep.' Chris Hoy is showing off his sleep kit. Sleep was one thing that people hadn't looked at in detail."

Team Sky reaped the rewards of Nick Littlehales' expertise

But before all this success on the road with Team Sky, Littlehales learned his trade in football, and was thrown into the deep end after a chance meeting with the Manchester United squad and a curious Sir Alex Ferguson - his sleep revolution was under way.

"I went from selling beds for Slumberland [based in Manchester] and soon I was talking to Sir Alex Ferguson and the Class of 92 about how best to recover and sleep," Littlehales says.

"My company were sponsoring Oldham Athletic, and I got asked to attend a film premiere that all the United players were at - it was a different time - so I just asked them what do they do in terms of sleep and recovery? Alex and David Fevre, the physio, were interested in what I had to say. Alex was just one of those guys who was interested in everything if it could help the club.

Manchester United's Class of 92 were the first to explore how sleep affected their game

"What Dave [Fevre] was interested in was that they had a player in Gary Pallister they had to wrap in cotton wool. As a product manager, they mainly wanted to know if I could help out with his setup at home. That then engaged the conversation about more what I could do.

"He was sleeping on a rock hard bed, I made some changes, Dave started to see some benefits, they no longer needed to spend £50,000 on an adjustable bed on the coach for Pallister.

"All the sleep experience I learned throughout my career came to fruition, and Dave was like 'wow, we can do something with this'.

"United started doing pre-season double-up training, morning and afternoon sessions, which was unheard of back then. Alex was then asking me: 'what can the players be doing in between?' So we cleared a room out at Carrington [United's training ground], put some loungers in, and encouraged the players to nap.

"Any other club, any other manager, any other set of players, it may have never been used. The Class of 92 were willing to do anything that would improve their game. Once they started doing it, everyone else followed. If David Beckham starts doing it, you are going to do it.

"The funny thing is, initially, we didn't know what we were doing. I wasn't a sleep coach like I am now. We learned as we were going along.

"Luckily, there were people like Ryan Giggs who was interested and so engaging with things that might help him with his life. He wasn't thinking playing of playing to his 40s back then, but if someone told him he could do something that would help, he would do it. He had an amazing attitude."

Wenger and Henry keen to learn

The rest of the Premier League started to take notice. The late 1990s saw a shift away from the drinking culture, with more emphasis on fitness and wellbeing at most clubs. One new French manager in particular, along with his superstar striker, was keen to hear what Littlehales had to say.

"United players were going away with England, and staying in these places with scratchy blankets etc, and they talked to the England staff, Gary Lewin especially, and he became intrigued," Littlehales continues.

"He then went back to Arsenal, told this new French manager [Arsene Wenger] about me, and then pretty much the first time I felt like a sleep coach was when I was put in front of the Arsenal squad in a conference room at London Colney [Arsena's training ground]. The Arsenal players found it very funny indeed. I mean, there was a guy talking to them about sleep.

"When the players weren't really concentrating, or interested, Thierry Henry stepped up and got them to pay attention. He was very interested and wanted to get as much out of it as he could.

Thierry Henry made sure his team-mates listened to Littlehales

"Then I'd be in the media room at Melwood [Liverpool's training ground] and I was lying on the table showing Steven Gerrard the best position to sleep in. The team doctors were getting too many questions about sleep, so in I came."

With so many elite clubs coming in for Littlehale's new-found expertise, it was only a matter of time until the FA came calling. The arrival of Sven-Goran Eriksson gave Littlehales that chance.

"England were going to be based in a hotel in Lisbon for the whole tournament at Euro 2004," he continues.

"We looked at the hotel, where the sun came up, so looked at protocols for keeping the sun out, adjusting the air con, pillows, duvets, linen, and layers to make the mattresses more comfortable from a postural care [body shape] point of view.

"That created a lot of press. Eriksson was a great media person, this team were full of superstars, and they were being told what to do by this sleep coach. People were like 'what are you doing?'"

United connection intrigues Ronaldo

From there came the meeting that Littlehales is best known for, a conversation between Carlo Ancelotti and the Real Madrid doctors, that unexpectedly piqued the interest of Cristiano Ronaldo.

"I got asked to go to Real Madrid as I had done a lot of work with Chelsea, with sports scientist Jack Nayler, Paul Clement and Carlo Ancelotti. They all teamed up at Real Madrid and were keen to get me in to talk to the squad.

"We went into their training facility, checked out all the penthouse rooms to see if we could improve them. Their medical side was not that good, and they knew that.

"Gareth Bale had just arrived. The whole first-team squad were all there when I came in to advise them. We were sat on the training ground pitch, going around talking to everybody. Ronaldo was training on his own because he was injured, doing some recovery training on the pitch.

"Ronaldo looked at me, and knew I had been working with Manchester United, and due to the massive connection he still has with that club, was interested; Manchester United's sleep coach was in the players' lounge. So several of them just stood on the edge and watched, Ronaldo being one.

Cristiano Ronaldo was interested with Littlehales' United connection

"Whatever we did still works, as Jack moved onto to Celtic and I am working with Celtic now. It is highly likely that players, like Cristiano Ronaldo, took it all on board. I mean, Gareth Bale is now promoting a mattress!"

So what's the secret? How do you tell a millionaire footballer how best to rest? Littlehales insists there are no expensive gadgets required, it is all about influencing the habits of players and trying to lessen the effects of the technological, 24/7 world.

"It is about sleeping in cycles," Littlehales says. "You need 35 sleep cycles in a week. 90 minutes is how we measure sleep cycles. Five a day gives you 7.5 hours. That can be three or four back-to-back and then a nap in the afternoon. You are just aiming for five cycles per day, on average.

"Players can look at their week, and work out how to get better recovery times through these cycles. Hotels and stress ahead of a game reduced chance of recovery, so we have to think more carefully about how we are going to get them to sleep.

It is about sleeping in cycles. You need 35 sleep cycles in a week. 90 minutes is how we measure sleep cycles. Five a day gives you 7.5 hours. That can be three or four back-to-back and then a nap in the afternoon. You are just aiming for five cycles per day, on average. Nick Littlehales

"Me and the coaches can look at the diary, and we work out how we get these 90-minute cycles in. 30 will be back-to-back, at night, but then we work out how we can get a full 90-minute cycle in during the day, through three 30 minutes or more 20-minute stints. It can just be a quiet 20 minutes with a towel over your head to block out the light.

"The Ryan Giggs and David Beckhams of this world had recovery times, naturally, between training sessions. Now, everything is 24/7. While players are waiting for the coach to bring out the balls for training, they are all on their phones right up until the last minute. It is a lack of mental recovery state.

"There has been no recovery education along this process. We have just wandered into this modern world without thinking of when I need to shut this tech down so my mind can recover.

So what now? Is Littlehales's work done? Has he educated teams and have they changed the way they think? The likes of Manchester City and Brighton are currently taking Littlehale's thinking to the next level and adapting their state-of-the-art facilities around getting their players the best rest time possible. City are especially keen, and with football becoming more and more about marginal gains, like cycling, it could be the difference between winning and losing the title.

Man City take recovery seriously

"Clubs around the world, Houston Astros baseball team, the Miami Dolphins, there are clubs who are now allocating budgets, and what to do something about this area. It is a different era now," Littlehales adds.

"From my relationship with United, I started working with Sam Erith [head of sports science] at Manchester City. He was massively into recovery and got me involved. We wanted to make this new, incredible training facility as much about recovery as possible.

"These rooms in the training facility are not palatial like they are at Real Madrid. They have blackout curtains, but they aren't grand. They are just based on recovery.

Littlehales has helped develop Man City's Etihad Campus

"Sam is very keen that they are educated, long-term. He wanted to make sure the players don't go out and buy things that will make their recovery time at home worse. I have been through most of the players privately to make sure they think about how they recover at home.

"They have reduced the number of hotel nights by 50 per cent. The players stay in these rooms before Premier League games. It is a controlled environment, where we know they will recover and sleep well.

"With Sergio Aguero and his team-mates, I am working with these on a regular basis. My relationship with Manchester City is ongoing, and we play a big part in their setup, to this day.

"But what we do isn't just for sportsmen it is for everyone. We all have to take our recovery seriously. We don't want to scare people, but there is so much we can all do to improve our lives. Footballers have benefitted from such simple changes, now we have a job to do to get the message out to everyone."