It was not so long ago that professional footballers would treat their bodies with little more care than a Sunday league player.

“At Liverpool, if we played an away game in the late ’90s, we’d get onto the team bus and there would be a couple of crates of lager,” Michael Owen tells The Athletic.

“You’d have to tick a box before kick-off to say whether you wanted chicken and chips or fish and chips after the game — and by the time you were halfway home, the whole bus was engulfed in cigarette smoke.” 

Fast forward to 2023 and modern-day football is worlds apart from the amateur game, most notably due to the detail with which players’ performance is objectively monitored — from the volume of passes made to the blades of grass covered.

We have grown accustomed to seeing players wear a GPS (global positioning system) sports vest under their shirts during a game, but it is worth highlighting how much wearable technology has grown in football and how it has ventured into new realms in recent years.

There is, quite literally, nowhere for today’s cohort of players to hide given the ubiquity of data in football.

“In our generation, you knew who had been out the night before, just from the positions they’d take up in training — they’d be on the left wing and they’d be doing nothing,” Owen explains. “Now, if you don’t do enough in training they’ll be able to look, and question if there is anything wrong with the player — physically or emotionally — but there is simply no hiding place anymore.”

STATSports and Catapult lead the industry as the most widely used GPS wearable devices in the professional game, with companies such as Barin Sports, and Hudl (WIMU Pro) also competing to provide the most cutting-edge performance tracking.

Across each device, the granularity of the information that is provided is extensive, with sensors that not only allow you to monitor the volume of sprints a player makes but also calculate the direction they are facing as they receive the ball and the balance they place on each respective foot.

It is one thing having a wealth of data logged for each player, but the real benefit of the technology is its ability to generate instant, actionable insight to a mobile device.

“In total, we have four sensors — the GPS, accelerometer, gyroscope and magnetometer — and you’re getting 660 raw data points per second,” explains Tiago Malaquias, senior data scientist at STATSports, which is used by hundreds of clubs worldwide including Arsenal, Liverpool, Manchester United, Juventus, as well as the Brazilian national team.

“That is a lot of data for a coach to be looking at, so that’s when you use the software to extract different metrics that the clubs can use.”

Unsurprisingly, some of the most commonly used metrics are those that support non-contact injury prevention, with clubs able to set individual thresholds for each player to ensure that they are not overloaded physically and provide real-time risk management to staff during a session.

“The coaching team can access the internal workload of a player such as heart rate and VO2 max (the upper limits of a player’s exercise capacity), and their external workload such as total distance and speed,” Malaquias explains. “Managing this throughout the week allows them to do their best to prevent player injury.”

“We cannot claim to prevent injury, but there are factors that you can control and these devices are crucial to doing that.”

Whether it is cutting the duration of a training exercise, adding extra players in the middle of the popular ‘rondo’ drill to reduce intensity, or simply making the pitch smaller in a practice game, the insight that this technology provides allows staff to mitigate the physical output of a player by tailoring sessions to their unique attributes — decreasing injury risk while maximising peak performance across a season.

For former players such as Owen, there is a poignant reflection on current injury prevention methods compared with his playing career.

“When I was 19, I had a horrific injury,” explains Owen, who is an investor and ambassador at Barin Sports. “I’m pretty sure that if this type of technology was around at that point, then I might have had a very different career — being at the top of the game for 15 years as opposed to six or seven years.”

“It annoys you in one way but also makes you think how great the technology is, that any big injury could now be detected before it happens, and not hurt anybody else’s career so badly. It’s an incredible tool to have.”

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Beyond injury prevention, the value of performance data is best when it is providing coaches with insight that is contextualised to a team’s match strategy.

In 2022, Catapult released the industry’s first platform that integrates player performance data with video analysis to be used pre-game, post-game and live in-game.

From analysing team shape (in and out of possession) to identifying the spaces between centre-backs, Catapult’s ‘MatchTracker’ combines player tracking data with real-time video to visualise what is occurring on the field. MatchTracker is the flagship product in Catapult’s Pro Video Platform, a comprehensive suite of performance analysis tools for training, matches and opposition scouting.

“The power of MatchTracker is its seamless integration of different performance datasets all aligned to video,” says Adam Chovan, senior product manager at Catapult. “Now, teams can quickly sort, filter, and view performance insights using a variety of data visualisations and instantly play video for the coach.”

That immediacy of such information is where the real advantage lies, and the uptake among clubs is growing. Beyond Catapult’s global clients — which include Paris Saint-Germain, Bayern Munich, Real Madrid and the French Football Federation — MatchTracker powers more than half of the Premier League’s teams’ tactical insights, and you may have already seen it in use on a matchday.

Fans will commonly see coaches gathered around pitchside monitors following a dubious foul awarded against them, but the primary use of this technology provides live tracking updates that allow staff to spot patterns and trends within the game based on the player performance data.

Integrated video or not, the output that GPS tracking alone can provide is a valuable source of information that can inform a manager’s tactical strategy as the game is being played.

“We can track distance between players, and distance between the lines — so team length and width,” explains Barin Sports’ Daniel Shopov.

“During a game, we measured how much the opposition was pressuring our team, as the defensive and midfield lines were getting closer together. That information dictated a substitution, so the coach ended up playing with a back five and allowing those lines to spread out. We were able to track this team shape in real-time and then combine it with the physical condition to know which player to substitute — and that’s where the combination between the tactical and the physical came together.”

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GA explained that the pre-match hold-up was due to Argyle & the referee questioning Wanderers’ GPS equipment, which is approved by the FL.

— Wycombe Wanderers (@wwfcofficial) September 12, 2015

Though we have become used to seeing upper-body GPS vests to measure physical metrics, more recent technology is emerging to monitor technical performance using lower limb tracking systems.

Having only granted approval for clubs to wear GPS vests during matches from 2015-16, the International Football Association Board (IFAB) has recently approved the use of technology company Playermaker’s AI wearable tracker straps on football boots to provide performance data including kicking velocity, ball touches, preferred footedness, and time on the ball — as well as established physical data such as technical balance, speed, distance and changes of direction.

The technology has grown in prominence since its inception, with FIFA’s chief of global football development and former Arsenal manager Arsene Wenger invested in Playermaker nearly four years ago. 

Playermaker now has partnerships with more than 200 clubs and organisations around the world including LA Galaxy, the English FA, and Borussia Dortmund — most recently working particularly closely with Manchester City to develop the next generation of technology called CITYPLAY.

Playermaker is not the only company on the market, with competitors such as Jogo and Xampion using sensors that are placed in the insole of each boot, while other companies, such as Zepp, Next11, and Oliver, have developed a calf sleeve that players wear under their socks.

Italian-based analytics company Soccerment has designed wearable shinguards called XSEED, which provide advanced analysis at grassroots level as well as the professional game. To highlight the growing prominence of the technology at the elite level, Soccerment recently announced Inter Milan wing-back Federico Dimarco as one of its key XSEED ambassadors. 

Alongside physical events, the technology uses artificial intelligence to train a neural network that can identify the technical events that occur on the pitch — distinguishing between a pass, a cross, or a shot — which are linked to an app for the player to instantly interpret their data. 

Most recently, Soccerment’s technology has helped them become the first company to provide expected goals (xG) metrics from the wearable shinguards. 

“Especially in youth football, having xG helps us to understand the decision-making process of a player,” said Aldo Comi, co-founder and CEO of Soccerment. “If you see a player taking shots from 30 metres away, you might question whether they should do that, but having this data across a long period helps you to understand the football IQ of a player.”

Much like the GPS vests, the advantages of such lower limb tracking systems extend beyond the individual level, but can be used across an entire team to provide contextual information on team shape, average player positions and distances to provide a holistic picture for match analysts to assess during the game to inform their tactical approach.

For those who weren’t sure, football’s next technological frontier is already here.

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Many of us will have our own wearable technology to track our everyday fitness — from an Apple Watch, Fitbit, or Garmin Watch — but the use of personal devices is increasingly popular among professional footballers as an additional source of information to monitor health, recovery and sleep.

For example, Liverpool centre-back Virgil van Dijk has joined Cristiano Ronaldo and Beth Mead in wearing fitness tracker Whoop, with the Dutchman recently becoming an investor as part of a global ambassador deal. 

Meanwhile, Barcelona and Spain star Alexia Putellas is known to be a dedicated wearer of an Oura ring, which can monitor heart rate variability, sleep patterns and fitness levels in a single piece of jewellery.

Given this ever-advancing landscape, professional athletes would be foolish not to use such technology to maximise their own physical performance. For Owen, the delicacy of a playing career at the top level cannot be undervalued.

“At the elite level, as soon as one tiny thing goes wrong, that could affect your whole career,” Owen explains. “Once you’ve had that big injury, once you’ve had that problem, there is no turning back. There is no margin for error, but if you can use technology to enhance decision making then it can only be a good thing.”

With the wealth of data on offer, these devices can allow athletes to monitor their fitness and rest at the physical level but also provide objective evidence for a player’s performance at the technical level during contract negotiations or recruitment.

“Players will be using their own data more and more to generate interest from clubs,” said Comi. “Kevin De Bruyne set the example a few years ago (using data company Analytics FC to support his contract negotiation), and I think this serves as a blueprint for what players can do with their own data.” 

“Even if you are not playing at the elite level, you now have a tool that can track your own data, and you can present to prospective clubs. That will be increasingly common in the future.”

Quite simply, today’s generation of players understand the value of performance data. 

The advancement of sports science and technology has catalysed such change, and with IFAB approving the latest lower limb tracking systems, the future of football looks to be only going in one direction.

Still, those post-match fish and chips must have tasted pretty good.

(Header image via STATSports; design by Sam Richardson)