The Fifa Women’s World Cup final this summer was remarkable, and not just because England came within one game of playing in it. One in 12 Americans watched at least part of the game live, making it the most watched football game in US history, while Team USA secured a record third title, thanks in no small part to their midfielder Carli Lloyd scoring a 13-minute hat-trick. The third of these saw her lob the Japanese goalkeeper from the halfway line.

Less obvious, but possibly of more significance, were the small black gadgets about the size of an old Nokia mobile phone that the winning players were wearing between their shoulder blades. The final was the first major international match since the laws of the game were changed in February to allow players to wear performance-tracking devices during a match.

Many believe it is only a matter of time before the technology is given the go-ahead in the Premier League and other major competitions. While managers have had access to post-match data analysis for years, the ability to use it to inform tactical changes and substitutions during the game represents a major shake-up in the world’s most popular sport.

And it’s not the only way in which science is muscling in on what has traditionally been the domain of managers and their coaching staff.

DATA

Modern football data analysis has its origins in a video-based system that used computer vision algorithms to automatically track players. Developed 20 years ago in France, as a tool for broadcasters, it was adapted as a coaching aid and first used at Derby County in 1998 by Leeds-based company Prozone. This and other video tracking systems use multiple cameras inside stadiums, and human operators who manually record data, to gather information on things such as possession, passes, tackles, runs, interceptions and shots.

“Until recently, it was very much about collecting data on what had happened, without looking at why it had happened,” says Paul Power, a data scientist at Prozone. Power cites the great Italian defender Paolo Maldini as an example of a player who might be marked down by a system that values tackling and intercepting; because his positional play was so good he had less need to do these things. This helps explain why, at an industry seminar in London in March, Power used a video clip of a shoal of sardines reacting to the presence of sharks to illustrate the more sophisticated approach rapidly gaining ground in football. “We’re reconceptualising football as a complex dynamic system, using complex systems theory, which is derived from chaos theory,” he says.

The idea is to capture more useful information about, for instance, inter-player co-ordination, players making themselves available for passes and the ability of players to block the passing options of opponents through positional play.

While some top clubs, including Chelsea and Manchester City, do basic video tracking-based number-crunching during games, most analysis is done post-match. What the majority of coaches want is to be able to use the live performance-tracking devices players wear in training sessions during matches. This is already done in other sports, including rugby (both league and union) and Australian rules football. It’s a change many expect to see in football within the next couple of years.

The International Football Association Board (IFAB) agreed to change the rules in February, so that league and competition organisers can allow the wearing of such devices by players during matches, as long as they are shown to be safe and the data is not received in the technical area occupied by managers and coaches during matches. This means that in practice it can be delivered to them at half time in the dressing room.

Team USA, who won this year’s Women’s World Cup, wore performance-tracking devices between their shoulder blades – a first for match-based tracking. Photograph: Nicholas Kamm/AFP/Getty Images

Last month, the IFAB sent a circular to member organisations, explaining that it was up to league and competition organisers to check these conditions are met. However, along with Fifa, the organisation is planning to launch a testing programme next year, which will certify devices that are safe and give them quality ratings. It has also announced a longer-term research programme into potential medical benefits.

Previous attempts to introduce new technology into the beautiful game have generated long-running controversies. Why kill off the fun of heated debates over disputed refereeing decisions and replace the unquantifiable components of human grit and determination with killjoy technology and spreadsheets? traditionalists howl.

These arguments, along with a desire to keep the game as similar as possible across all levels, have been weakened by what is widely seen as the successful introduction of goal-line technology. Some senior football figures fear in-game tracking devices will give wealthy teams an advantage; however, such concerns are being eclipsed by the view that the systems could benefit players’ health, including the suggestion that they could prevent the handful of deaths of players from cardiac arrest each year.

Some believe the devices could prevent the handful of deaths of players from cardiac arrest each year

There is also a growing realisation that attempts to enforce a ban on ever smaller pieces of technology is increasingly difficult, if not impossible. “It’s very difficult to track, from the referee’s perspective,” says Lukas Brud, secretary of the IFAB, “and one of the reasons we decided to allow it is [because] we cannot stop players wearing tiny chips and devices if they really want to. And if there is a correlation with injury prevention and proved medical benefits, these may be valid reasons for allowing those systems into the technical area for medical staff, in future.”

Brud suspects some devices may already be being used discreetly in some matches, although there was nothing surreptitious about Paris Saint-Germain striker Zlatan Ibrahimovic’s use of his: two years ago, he managed to alarm both footballing authorities and fashion commentators after removing his shirt, following a friendly against Real Madrid, to reveal a compression vest, containing a GPS unit, that bore more than a passing resemblance to a sports bra.

TRAINING

The two main performance-tracking systems currently used by Premier League teams in training are Catapult Sport’s OptimEye S5 and the STATSports Viper, both of which slot into compression vests worn on the upper body. As well as GPS sensors, these contain accelerometers, magnetometers and gyroscopes, to pick up extra information on impacts, jumps, changes of direction, acceleration and deceleration. The Viper also has a heart rate receiver.

Leicester City players using Catapult Sport’s OptimEye S5, which slots into a compression vest and records impact, acceleration and more. Photograph: Neil Plumb/Plumb Images

The technology’s main function is to help coaches calibrate each player’s training routines, including those recovering from injury. If players either under- or over-perform in a session it can be an early warning of injury.

“If you drove a car without a dashboard, you wouldn’t know how fast you were going, how far it had driven, and how much fuel was left in the tank,” says Boden Westover, director of marketing at Melbourne-based company Catapult.

Devices are currently being tested which will provide more information, with the addition of sensors measuring things like perspiration, as well as adrenaline and cortisol levels.

Researchers are also investigating the use of “smart” pills, which could provide body temperature data to smartphones or tablet apps, so that workouts could be tweaked based on the effects of small changes in muscle temperature on physical capacity. There are also training systems that use sensors in shoes and footballs, such as the Adidas miCoach Smart Ball, to pick up extra information, such as power and spin placed on shots.

SLEEP

While fine-tuning the exertions placed on players’ bodies is one side of the performance coin, the other is helping them to recover. Within that there is a growing emphasis on the physiological processes that take place when their eyes are closed.

Basketball players who slept for 90 minutes longer than normal improved their sprint times and shot accuracy

“Research tells us that sleep is really important for physiological recovery,” says Alek Gross, head of sport science at Southampton FC. “There is certainly a correlation between poor sleep and things like reaction times and ability to produce power.”

In 2011, scientists at Stanford University found that basketball players who slept on average for more than 90 minutes longer than normal significantly improved their sprint times and shot accuracy.

Gross’s players are educated in the importance of how to prepare for sleep, optimising room temperature and avoiding blue light from electronic devices within 90 minutes of going to sleep. They get sleep kits, including personalised mattresses, when they stay in hotels.

Players at most professional clubs fill in daily well-being questionnaires on smartphones or tablets. Those identified as poor sleepers are given wristbands, such as the Fatigue Science ReadiBand, which uses movement sensors to assess sleep quality, so that problems can be diagnosed and efforts made to resolve them. Large clubs have also installed beds at their training grounds – “snoozeboxes” and “sleep pods” – to allow players to sleep between sessions.

Swansea City use ‘sleep pods’ to allow players to snooze between training sessions. Sleep is now seen as key in effective physiological recovery. Photograph: Aled Llywelyn/Athena Pictures

Everyone’s physiological responses vary according to light and time – reactions known as chronotypes. That’s why establishing whether players are natural early or late risers, and therefore when their bodies are able to perform at their peak, is the starting point for Nick Littlehales, a sleep coach who has worked with players at Real Madrid, Manchester City, Arsenal, Chelsea and Southampton. “If you’re involved in a Champions League game that goes to penalties at 9.50pm, player chronotypes could make all the difference,” he says. “Taking recovery more seriously can have benefits on alertness, awareness, reaction times, relationship building, anger management and internal organ health, and trigger performances we don’t even know are possible.”

He also advises that players take account of their chronotypes when planning how to fit the five full 90-minute sleep cycles they need for full recovery around training and matches.

PSYCHOLOGY

Even if physical performance can be maximised, and parameters including those involving multiple players can be measured and plotted on graphs, there remains an important element of the game that can’t be tracked. The confidence, group spirit and the individual hopes, dreams and fears of players also play important roles in determining the final score.

If you're in a Champions League game that goes to penalties at 9.50pm, your chronotypes could make all the difference

This, along with recent experiences in other sports, helps explain why psychology is gaining greater acceptance within football. Dr Steve Peters, for example, worked with cyclists, track and field athletes and snooker star Ronnie O’Sullivan before more recently helping Liverpool and England footballers. “It’s certainly an expanding area, though I’d say it’s still under-utilised in football compared with other sports,” says Bradley Busch, of Inner Drive, a London-based performance psychology consultancy.

Busch, who has worked with players at Tottenham, Sunderland and Crystal Palace, teaches techniques for use both during the week and on match days, including helpful “self-talk” methods for each player, emotional control, performing under pressure and concentration. “We teach them to focus on things you can influence and control, such as their roles on the pitch, movement and attitude,” he says. “Some players dwell on mistakes, like a bad first 10 minutes, a missed penalty, or the consequences of defeat. During the week, having some focus on learning from mistakes and future goals can be motivating, but in the 30th minute of a football match, your focus needs to be on the 30th minute of a football match.”

Do the scientific inroads into football mean it’s game over for those for whom the seemingly random and unquantifiable are central to the human dramas played out on the pitch? Despite being an eloquent advocate of the power of data in the game, Prozone’s Paul Power thinks not. “There are always intangibles that are very difficult to capture. Anyone who thinks everything can be reduced to data is probably deluding themselves.”