The former is an established part of any footballing set-up worth its salt, but what about the latter? “There’s awareness in the industry that this has the potential to be a key factor, but it’s difficult to do studies,” says Barry Drust, an applied exercise physiologist and former sports science consultant at Liverpool. “A football club is not going to stop half of its team sleeping to see if the other half perform better.”

“IT’S POTENTIALLY THE TEAM THAT RECOVERS BEST THAT CAN HAVE THE HIGHEST SUCCESS”

That said, there are benefits arising from sound sleep that are widely agreed upon, including improved muscle recovery after training or matches, better reaction times on the pitch and greater decision-making capabilities. However, while those are three very good reasons for any sensible footballer to favour early nights, the nature of their job makes that easier said than done.

“Think of a footballer playing an evening game in Europe,” says Drust. “It’s likely that the player will have had certain supplements, such as caffeine, to help him perform. Then he’s flying back to his home country and, even though he may be on a chartered flight, his opportunity to sleep is not the same as it would be if he was in his own bed. Then he gets home in the early hours; he may have young kids, gets woken up early and wants to get involved in family life. Then he has to factor in time to prepare for a game.”

Nick Littlehales, a sleep coach who has worked with Champions League clubs such as Real Madrid, points out another issue. “Although it’s getting better, consistency is the biggest problem in football. Some managers come in and they’re only interested in whether they can get three wins back to back, not necessarily the long-term health of the players. Some of the human beings in this process get forgotten.”

That’s not to say that every club is sleeping on the job. RB Leipzig, Tottenham, Real Madrid and Manchester City, among others, all provide accommodation at their training grounds, so that their players’ sleeping environments can be regulated, consistent and personalised (“They can take their teddy bear in there,” says Littlehales, smiling). There’s also more thought going into the choice of hotels for away games. “You want to choose one where they’re open to things being moved about in the room – some of the more elaborate ones aren’t,” adds Littlehales. “There are things to think about: does a player sleep on a particular side of the bed at home, facing the window? If you can’t move the bed in the hotel they might be facing the opposite way to usual, so they could be agitated all night.”

The first club that Littlehales advised, back in the mid-1990s, was Manchester United. David Fevre was the physiotherapist at the time and he recalls: “When you go to hotel rooms you’ve got different types of pillows, different types of mattresses; we wanted to try and keep everything normal for the lads. We took pillowcases, pillows and toppers in a great big holdall. Scholesy [Paul Scholes] was asthmatic so he had his own special pillows. Henning [Berg] had a stiff back so we used to give him his own mattress.”

Clubs also advise their players on sleep hygiene, which has got nothing to do with checking your armpits before turning in. Instead it’s about creating optimal sleeping conditions: a temperature of about 18C, not going to bed on a full stomach and avoiding devices with bright screens in the lead-up to bedtime (this can even extend to putting black tape over TV standby lights in hotel rooms).

In other instances, players have taken their slumber success – or lack thereof – into their own hands: Robert Lewandowski has had sessions with a personal sleep coach, Gareth Bale advised on the design of an aeroplane-specific mattress and Man United’s Andrea Pereira visited a hypnotherapist to help him sleep the night before away games.

Clearly, then, sleep is a prominent feature on the football landscape. And with its intricacies and effects not yet fully understood, many clubs have turned to wearable technology in an attempt to monitor their players’ sleeping habits. But is that a shot in the dark? “Some players respond very well to the information and find it helpful,” says Bloomfield. “Others see it as an invasion of privacy, or are concerned that the results could impact their next contract.”

Drust elaborates: “If you’re a professional footballer, there’s a huge scrutiny around what you do. Some of that is legitimate, because people are trying to optimise your performance. But there is a line. Just because you can put a monitor on somebody, at what point does that become counterproductive for the player as a person? It’s a delicate balance to strike, making sure you’re providing support but not creating a 24-hour surveillance culture where people can’t switch off.”

Given the difficulties of compiling evidence-based assessment, sleep science’s role in football is always going to be difficult to pin down. “We don’t necessarily understand all of the implications,” says Drust. “But I’m certain it will be an area for development over the next few years, because more and more people are taking an interest.”

In the meantime, let’s sleep on it.