NETWORK THEORY CAN BE APPLIED IN TECHNICAL DECISION MAKING
Applying network theory to football is simply one more method to obtain additional information about a football match.
While FC Barcelona’s training sessions take place, their trainers follow on-screen a complex series of graphics, which correspond to the individual performance of the player and the result of the plays they practice in group. The data is provided by an EPTS (Electronic Performance and Tracking Systems) called WIMU PRO, whose set of measurements are added by a computer program. The club was not only one of the pioneers in the implementation of this type of device, now common in all major clubs but also contributed to the joint development with the manufacturer.
Using the kinetic and kinematic information provided by the device, trainers can measure the speed at which the player is moving, the exact point at which he has jumped to head the ball, or if he has made a turn to boost himself. Jumps, impacts, or collisions between players are also captured and recorded, allowing to calculate distances, accelerations, and speeds, as well as other useful data.
To collect these measurements, the players carry the WIMU PRO with them during the session. It is about the size of a garage door opener and weighs only 70 grams. It houses a series of very precise sensors capable of recording individual movement. The inertial sensors: accelerometer, gyroscope, magnetometer, and barometer – and the positioning sensors by means of geolocation. All these technologies already existed, incorporated into mobile phones, but in the WIMU PRO they have been combined in a specific way to measure the activity of athletes and record the results. In addition, the device can be connected to external sensors to measure physiological data, such as heart rate or muscle activity measured by surface electromyography.
Before using the WIMU® product, Barça tried out other EPTS devices, finally deciding on the one manufactured by Real Track Systems due to its potential for improvement. Once developed, this has been materialised with the following: not limiting its use in closed or uncovered spaces, and delivering raw data.
One of the common problems in EPTS is the possible interruptions in data measurement. Even if the sensors do not stop working, the transmission of their signals can be interrupted by multiple factors, such as bad weather conditions or reception failures, coverage black spots, or training in closed areas. The solution provided by RealTrack, called Hybrid System, is to combine two satellite navigation systems, GPS and UWB (Utltrawide Band). The UWB receives the signal from a set of antennas that, placed in different points in the pitch, simulate the satellite system, and combine with it to minimize data loss. This way the accuracy of the player’s position and trajectory measurements is +/- 10 cm.
Another advantage of the WIMU® system is its data analysis software. All members of the technical team who are granted access can log on to the platform, and see the graphs that show how each player, and the team as a whole, is performing. This information is displayed in real-time, and the user can replay the play along with the data. In addition, depending on the speciality, the tool can be customized to analyse and see that which is thought to be most interesting or relevant. It can be physiological variables -heart rate, muscle activity, etc.- or tactics, -Voronoi diagrams, Delaunay triangulation, line and area relationships… Although this is done by the data analysis team at FC Barcelona with another partner.
During training sessions, Strength and Conditioning coaches use between 10 and 20 of the more than 100 variables provided by this EPTS device. Depending on the session and to whom this is intended (it is not the same what a coach wants compared to the medical staff) these different variables are selected to create specific reports, comparing data from different sessions, identifying patterns, planning recoveries after the season of inactivity, or monitoring the external load of each player. The range of possibilities and customization is also a result of the joint work developed between the technical staff and Real Track receiving the feedback in order to incorporate these modifications to enhance its use. In such a complex team, in which not only the assistant coach and the physical trainers take part, but also the tactical, technical and physical performance analysts, as well as the medical team, it is essential to segment the metrics to provide very precise and specialized information to each of these groups.
The use of WIMU PRO in Barcelona seeks above all to adapt to each type of coach and provide him with what he asks for, regardless of whether he is one of those who only want to know how long he has played or one of those who seek to know how each player performs in a specific task. However, the use of an EPTS like this cannot answer the eternal dilemma on the appropriate profile of a coach. It has a superior intelligence to interpret data and propose game tactics, or a superior ability to manage a group formed by the best players in the world. Both profiles win World Cups, European Championships, and leagues, so there may not be a single answer. What is clear is that neither can give up the use of technology in high competition. Or in other words, an EPTS to master them all.
Although there are several studies on this topic, many of them have analyzed these demands by looking at just a few variables or using very broad timeframes. A new study completed by physical trainers from F.C. Barcelona has analyzed several of these details more closely.
The understanding of the modifying variables of the game, based on the degrees of freedom.
Sports Analytics has grown exponentially thanks to IT sciences and it also encompasses other subareas (e.g. sports sciences, behavior sciences, medicine or data visualization) in addition to statistics with a focus that is more tactical and sports performance related.