Those tight-fitting vests you see soccer players wearing under their jerseys hold a small GPS tracker and motion sensor between the shoulder blades. The device records physical data throughout training sessions and matches, giving coaches and sports scientists a detailed picture of how hard each player is working, how far they’re running, and whether they’re at risk of injury.
What the Vest Actually Contains
The vest itself is just a compression garment designed to hold a small sensor pod in place against the upper back. That pod, roughly the size of a small phone, sits in a pocket between the shoulder blades because that spot stays relatively stable during explosive movements like sprinting, jumping, and changing direction. The snug fit keeps the device from bouncing or shifting, which would compromise the accuracy of the data.
Inside the pod is a GPS chip, an accelerometer, a gyroscope, and often a heart rate sensor or a connection point for a separate chest strap. Together, these components track where a player is on the pitch, how fast they’re moving, how quickly they accelerate and decelerate, and how their body is responding internally to the effort. FIFA officially classifies these devices as Electronic Performance and Tracking Systems (EPTS) and launched a quality program in 2017 to ensure they don’t pose any danger to players.
What Data the Vest Collects
A single session can generate dozens of data points. The core metrics include total distance covered, top speed, number of sprints, acceleration and deceleration counts, and a composite training load score that factors in both physical and cardiovascular strain. Heart rate data, either from an integrated sensor or a paired chest strap, adds an internal picture of how hard a player’s body is working relative to their maximum capacity.
Some systems track more than 20 individual metrics per session. The raw numbers feed into software that visualizes everything from sprint patterns to positional heat maps showing exactly where a player spent their time on the pitch. This turns a 90-minute match into a spreadsheet of objective performance data that coaches can review within minutes of the final whistle.
How Coaches Use the Data to Prevent Injuries
Injury prevention is one of the biggest reasons clubs invest in this technology. Soft tissue injuries, particularly hamstring and muscle strains, often follow predictable patterns of overload. When a player’s sprint distance or high-intensity running spikes sharply compared to their recent average, the risk of a non-contact muscle injury climbs significantly.
A 2024 study in the Journal of Sports Science & Medicine built a machine learning model using exactly this kind of vest data from professional soccer players. The model identified seven key indicators of injury risk, three related to short-term spikes (number of sprints, training load score incorporating heart rate and muscle load, and time spent with heart rate above 90% of maximum) and four related to cumulative load over the previous four weeks (total distance, high-speed running distance, sprint distance, and overall training load score). The model predicted injuries with 78% accuracy and correctly identified 73% of players who went on to get hurt.
In practice, this means a sports scientist can flag a midfielder whose sprint count jumped 40% above their four-week average and recommend a lighter session the next day. Over a grueling season with 50 or 60 competitive matches, that kind of load management can be the difference between a player staying fit and missing six weeks with a torn hamstring.
Tactical Insights From Positioning Data
Beyond fitness and injury, the GPS data reveals how well players execute tactical instructions. Coaches can see whether a back line is holding its shape, how compact a team stays when pressing, and whether a winger is drifting too narrow or too wide during transitions. Every player’s position is logged multiple times per second, creating a real-time map of team structure.
Research in Frontiers in Sports and Active Living found that tracking data can characterize a team’s tactical behavior up to three times more effectively than traditional match descriptors like possession percentage or pass completion rate. By analyzing positioning patterns across multiple games, analysts can identify a team’s preferred formations, pressing triggers, and defensive principles. Coaches also use opponent tracking data, when available, to spot weaknesses to exploit: gaps between lines, slow defensive transitions, or predictable rotational patterns.
For individual players, the data can show whether someone is consistently arriving late to defensive positions, failing to make recovery runs at the required intensity, or not covering enough ground in specific phases of play. These conversations become easier when backed by objective numbers rather than a coach’s subjective impression from the sideline.
Are They Allowed in Competitive Matches?
Yes. Under Law 4 of the Laws of the Game, players can wear EPTS devices during official matches organized by FIFA, continental confederations, and national associations, provided the technology has passed the FIFA Quality Programme. The rules specify that the devices must not be dangerous to the wearer or other players. Competition organizers are responsible for ensuring the data transmitted to the technical area during matches is reliable and accurate.
Players are otherwise prohibited from wearing any electronic communication equipment during matches, so the EPTS exception is notable. Substitutes, substituted players, and even sent-off players fall under the same restriction, with the tracking vest being the sole permitted electronic device.
Professional Systems vs. Consumer Trackers
The vests used by professional clubs come from specialized companies like STATSports, which supplies FIFA-approved tracking technology to elite teams across soccer, rugby, and other sports. Professional-grade systems pair wearable pods with stadium-installed cameras or local positioning systems to improve accuracy beyond what GPS alone can deliver, particularly for indoor facilities or dense urban stadiums where satellite signals weaken.
Consumer versions of these trackers are now available for amateur players and youth academies, often at a fraction of the cost. They track similar metrics (speed, distance, sprint counts) and sync with smartphone apps. However, differences in hardware quality, filtering algorithms, and sensor placement can produce varying results between devices. A study in Frontiers in Sports and Active Living noted that two systems with theoretically equal accuracy can display different numbers simply because of differences in setup and data processing, not because one is truly less capable. For recreational players, consumer trackers still provide useful trend data over time, even if the absolute numbers don’t match professional-grade precision.
Why the Vest Sits Where It Does
The upper back placement isn’t arbitrary. Positioning the sensor between the shoulder blades keeps it close to the body’s center of mass, which produces cleaner acceleration data than a wrist or ankle-mounted device would. It also keeps the pod out of the way during heading, tackling, and shoulder-to-shoulder challenges. The compression fabric holds everything flush against the skin, so there’s no dangling hardware that could catch on another player or shift during a change of direction. Most pods weigh well under half a kilogram, light enough that players report forgetting they’re wearing them within minutes of warming up.