How GPS tracking is changing football

By João Medeiros

On June 17th Neymar, one of the world’s greatest footballers, will step out with his Brazilian teammates onto the turf at the Rostov Arena in Russia to face Switzerland in their first game of the 2018 FIFA World Cup. The team will be dressed in its distinctive canary-yellow strip. Underneath, each player will also wear a black compression vest with a tracking device slotted into a pouch between the shoulder blades. Called Apex, this tiny black computer, made by STATSports, contains an array of sensors. These include GPS to track position, accelerometers to gauge pace, gyroscopes to measure orientation in three dimensions and magnetometers to record the direction of travel. The device also contains an embedded processor that synthesises the raw data and computes, in real time, performance metrics such as distance covered and number of sprints completed.

In the past 20 years the use of GPS wearables in sport has grown dramatically. Catapult Sports, a sports-technology company, developed its first prototype in 2000: a 3-inch tube. “We thought it was amazing we could get that sort of information from something so small,” says Allan Hahn, one of the scientists involved in the project. “Of course, by current standards, it was huge. We had to tape it to the athletes with elastic bandage straps.” Today, Catapult is used by more than 100 football teams worldwide, 19 American football teams, 18 basketball franchises, including the Golden State Warriors, the reigning world champions from California, as well as high-performance institutes that support Olympic teams in over 25 countries.

Although wearable GPS devices have been a common sight on training grounds for a while, they have been deployed in competitive matches only recently. In February 2015 the International Football Association Board approved the use of electronic tracking in official fixtures, just in time for that year’s Women’s World Cup, hosted by Canada. In March 2018 FIFA announced that team analysts were now also allowed to transmit data and communicate with coaches during the match itself.

For the first time, the information gathered has the potential to influence the course of a game. “You will see unprecedented fitness levels in players,” says Barry McNeill, a senior executive at Catapult. Coaches will also be informed quickly of a player’s declining intensity. In theory, this should lead to less chaotic and error-strewn periods of extra time, when players’ decision-making falls away as they get tired. It will be especially useful in determining who to take off for the fourth substitute now allowed in extra time. The result, in theory, is that more players will spend longer playing at the top of their game.

Wearable GPS devices record measurements hundreds of times each second, dissecting and quantifying the physical dimension of sport into its various components: from the total distance covered to the number of accelerations, from heart rate to the force of impacts from tackles. Since GPS devices are now used both in training sessions and matches, by domestic clubs and national teams, the data allow fitness coaches not only to quantify the specific physiological demands of each game but also to ensure that the players are being trained to meet them. For example, a few members of the Brazilian team still play in their domestic league, where matches are played at a slower pace than international football. Guilherme Ramos, a physiologist at the Brazilian Football Confederation, says that he explains to these players exactly how much effort they will need to put in during the World Cup so that “whenever they play against a smaller team, they know that they still have to play with the same intensity as they would be if they were playing for Brazil.”

Training players for the most vital moments of a football match – when players have to sprint repeatedly with only a few seconds of recovery time in between – is particularly important. Tim Gabbett, a sports scientist who regularly works with elite performers such as Barcelona Football Club and Cirque du Soleil, calls these moments “worst-case scenarios”. A player may regularly cover 10km in a game but simply ensuring they rack up similar statistics each week is insufficient. “Players need to train for the critical moments. They are the most fatiguing and typically occur before goals are scored,” he says. Fitness is not just a matter of running faster and longer: tired players are more prone to making mistakes.

Using GPS data to prescribe precise training workloads is not just crucial to enhancing performance; it’s vital for ensuring that players can perform at all. In a 2016 study published in the British Journal of Sports Medicine, Gabbett and collaborators from the University of Wollongong analysed data provided by 53 top-level rugby players over the course of two rugby league seasons. They discovered that an increase in the ratio between the “workload” accumulated during the past week and that over the previous 28 days is associated with an increased risk of injury. In further studies, they found that when a player has worked twice as hard in a week as they did in the previous month, there is, on average, a 15% chance of injury (three times higher than when the ratio between the two figures is 1.3). Data analysis will be particularly useful to coaches at the World Cup, since players will have just finished strenuous seasons with their clubs. “If a player arrives and the club hasn’t shared any GPS information about him, then the coaches really have no idea what’s the optimal workload for that player,” Gabbett says. “You’re really just guessing and setting the player up to fail.”

That shouldn’t be the case with the Brazilians. In March, Brazil’s fitness coach Fábio Mahseredjian travelled to Europe to meet his counterparts at Barcelona, Real Madrid, Paris Saint-Germain and Manchester City, where some of the team’s top stars currently play. Mahseredjian asked each one to fill in a four-page form that included questions regarding players’ body composition, recent injury history, nutritional supplements, personalised training programmes and GPS data. After the World Cup, the Brazilian Confederation will return the favour, sending a report to each team detailing the workload that their players endured during the tournament.

The Brazilian fitness staff claims that since their players started using GPS wearable devices in 2015, soft-tissue injuries have been rare. Ramos, the physiologist, recalls that during the Rio Olympics in 2016 he needed to have a word with Neymar because of the exceptional number of high-intensity sprints registered by his GPS device during training. “We had to tell him to slow down or else he would get injured.” If he had, he wouldn’t have been on the pitch to score the winning goal in the final against Germany. Whoever strikes the decisive shot at this year’s World Cup will probably have done so with a computer at his back.

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