A Very Very Brief History Of Wearable Tracking In Team Sports
Since the early 2000s, IMUs with GPS tracking have been used to track athletes in team sports to monitor their performance. Some of them also integrate heart rate data from heart rate chest straps. When it all first started, there were 2 main companies/brands that developed and sold athlete tracking systems (using IMUs and GPS) – Catapult Sports and GPSports (GPSports was later acquired by Catapult). As both of these companies originated from Australia, it’s no surprise that the early adopters of these tracking systems were Australian (Rules) Football Clubs and Australian Rugby Clubs (League and Union). By around 2010, with a few other products in the market (VX Sports, Zephyr, Polar etc), athlete tracking has gained a bit more traction in the world, and also got into other team sports such as soccer and (field) hockey.
The Vest/Tank Top
Other than the Zephyr and Polar systems which are basically heart rate strap units with motion sensors and GPS embedded within them, the other systems relied on a tank top vest (like a sports bra) and the sensor device sits in a pouch/pocket at the athlete’s upper back. Research has found that is the most unobtrusive and effective spot to place the GPS tracker. Initially, some people were feeling funny about that tank top, but it became the norm very quickly in the mid-2010s. That’s likely because people realised the benefits of athlete monitoring and load/effort monitoring. By the end of the 2010s, there were probably around 20 companies/products in the market selling pretty much similar solutions in terms of hardware technology and some even do indoor/local position tracking (which doesn’t rely on satellites). FIFA has since developed standards to govern the use of wearable GPS trackers and other forms of tracking systems (in soccer) and they all fall into the category of Electronic Performance & Tracking Systems (EPTS).
What The Wearable Trackers/Sensors Do?
In the top end of Wearable Trackers/Sensors (eg Catapult Vector), athletes wear a vest with integrated heart rate sensors and the sensor device (that is inserted into the vest) has the typical 3-axis Accelerometer, 3-axis Gyroscope (angular rate sensor), 3-axis Magnetometer and Antennas for the satellites and the local tracking system. So with these sensors, the clubs/coaches can track:
- The athletes’ positions on the field and in relation to other athletes
- The distances they have covered
- How fast they are running (speed) and accelerating, turning, jumping
- How often they are sprinting at various speeds
- If they had any impacts/clashes and how often
- The athletes’ heart rate in relation to all that is happening throughout a training session or game
What About Tracking Kicks Or Passes?
Basically, any movement of the athlete or more specifically, the athlete’s torso, can be tracked by the Wearable Tracker. Then those movement data combined with analytics (backed by sports science research) produce actionable insights that could lead to better athletic performance and reduce potential risks of injuries. But in terms of specific activities and metrics like the number of shots or passes, stride length, kick/strike speeds etc, any movement specific to the leg/feet cannot be properly tracked/identified by those sensors placed on the upper back of the athlete. Although computer vision and pose estimation algorithms have made it possible to track an athlete’s whole body movements, we do need proper footage of the athlete without any occlusion, and that is quite impossible to achieve on a soccer field with 22 players. So quite simply, in order to track a player/athlete’s kicks or passes, the most feasible option is to have sensors on the athlete’s leg or feet.
Soccer Specific Sensors
Here, I am going to look at seven different sensor products that are designed to be worn on an athlete’s calf or feet, with the capability of tracking soccer-specific activities. Four of them are worn on the calf (near the knee and usually at the back of the calf) and the other three at worn at the feet (either inside the soccer boot or attached to the soccer boot). I will cover the hardware, how each one works, what metrics they capture, and their availability and I will do an overall comparison at the end.
Calf Sensor 1: Footbar (Meteor)
First off, we have Footbar. Founded back in 2014 in France, they have developed a wearable sensor (Meteor) meant to be strapped to a soccer player’s calf just below the knee. Although they don’t specify which leg to strap the sensor on, logical thinking would have a player place the sensor on their dominant striking leg. So here are the deets:
- Hardware: 1 x Meteor sensor, Strap, USB Adapter for charging.
- Connectivity/App: The Footbar smartphone app is used to connect to the sensor (via Bluetooth), turn on the sensor, sync the sensor data after each game/session, analyse the data and let the user monitor their progress.
- Metrics: The sensor with its smart algorithms identifies the following (Technical and Physical) metrics. In terms of ‘Technical’, there’s the number of shots, speed of the shots (max & average), number of passes, dribbling times, and possession time; then in terms of ‘Physical’, there’s running time, distance covered and sprints statistics.
- Analytics: Based on the data, the app is able to identify the user’s playing style, and overall performance, and provide a coach analysis
- Gamification: The app allows the user to track their progress over time. On top of that, the user gets their own FIFA style player card with similar attributes, so they can have some friendly competition with their teammates.
- Team Solution: For teams/clubs, Footbar provides a web interface to monitor and manage the entire team’s performance in terms of technical and physical stats. Teams or clubs who are interested can reach out to them to find out more.
For accurate tracking of the different activities, the Footbar team states that the strap must be worn just below the knee. That is how they have developed their tracking algorithm. At the time of writing/publishing this, they are predominantly in France and are available at Decathlon stores. They have also partnered with some of their local football clubs/facilities and event organisers so that players playing at those facilities or events can try out using the sensor. Players everywhere else can simply purchase the sensor directly from their website.
Calf Sensor 2: Zepp Play Soccer
Zepp was first known for its golf sensor that attaches to a glove and analyses a golfer’s swing. Taking the same idea of analysing swings, they took that know-how and applied it to tennis, baseball and softball and had the sensor attach to the bottom of the rackets or bats. Then in 2016, they developed a sensor product to analyse soccer kicks. Similar to Footbar, they utilise a single sensor unit (with a 3-axis accelerometer and 3-axis gyroscope) and they made a calf sleeve with a pocket to house the sensor. Here are the product specs:
- Hardware: 1 x Zepp sensor, Calf sleeve, Charger.
- Connectivity/App: The Zepp Play Soccer app connects to the sensor via Bluetooth and users can use the app to sync/manage data from the sensor/s, monitor progress and capture video highlights.
- Metrics: Captured metrics include distance covered, speeds (max), distance at different speeds, number of sprints, number of kicks (on the leg with sensor), kicking speed, and goal conversion rate (requires manual entry of goals) and active time. After each game, the app provides statistics for that session and updates the user’s profile with “Personal Best” stats.
- Team feature: For multiple players who have the Zepp sensors, the tracking can be initiated as a team practice or game and have all the data collated. So that at the end of the session, they can see the overall team performance and summary stats.
- Additional Sensor: Users have the option of purchasing another sensor to track the other leg. This can be helpful for training the ‘weaker’ leg and being able to compare and track the progress.
One thing I noticed about Zepp is that they have been acquired by Huami (the wearable division of Xiaomi) back in 2018. The sensors are sold on Amazon but at the time of writing this, they were not available. It also says on the app store that their last app update was May 2019. So I am unsure if Zepp is still continuing with the product or not.
Calf Sensor 3: Oliver
Next, we have Oliver and they are based in Barcelona, Spain. Starting in 2017, they developed what appears to also be another calf motion sensor with accelerometers and gyroscope, except it also houses a GPS module. So it is basically a GPS tracker but designed to be worn at the calf and is able to track and monitor football specific skills. They have developed a user platform (app) for players and there is also one for coaches to manage their players/team and teams can purchase a team version. Here’s a look at what’s included:
- Hardware: For the player – a calf sensor, shin guard covers/sleeves (2 sizes included), charging cable; For the team – number of sensors and sleeves as required, charging case/carrier.
- Connectivity/Apps: The sensor can sync and connect with the player/coaches app via Bluetooth (5.0). The player’s app allows players to see their own performance and compare with other players on the platform. The coaches’ app shows more team metrics and allows the coach to monitor and analyse every player’s performance over time.
- Metrics: They break down their metrics into 2 categories – Soccer and Athletics metrics. For ‘Soccer’ metrics, they provide the Heat map and interactions with the ball (ball strikes, kick force/power and ball possessions). For ‘Athletics’ metrics, they consist of activity time, distance travelled, maximum speed, sprints, accelerations and decelerations, jogging and walking distance.
- Analytics: Based on the data/metrics collected, the Oliver platform is able to provide the monitoring of loads, external and internal, measuring/calculating the risk of injury and calls to action that prevent injuries up to 45% per season (as claimed on their website).
- Gamification: The player’s app allows them to compare their performance with other players from all over the world according to type, age and position on the field and challenges them to participate in the constant challenges on the platform.
One thing about the Oliver is even though it has got GPS tracking, it is not live. Sensors collect the data of the players during each session. Then after the session, the app connects to the sensor/s and syncs or downloads the data for analysis. Also, interestingly, the Oliver sensors only capture IMU data (from accelerometers and gyroscopes) at 50Hz while most other sensors do it at 100Hz. Lastly, for coaches who are interested in the team option, there does not seem to be a standard package and interested parties are asked to contact Oliver for more information.
Calf Sensor 4: Next11
Next11 is the newest entry in this (Calf sensor) category. Founded in 2018 in Denmark, the Next11 team has developed a sensor that is worn at the player’s calf with a calf sleeve (similar to the previous 2). The main difference is the Next11 solution is meant for an entire soccer team and it not only tracks what each player is doing, but the system also tracks the players’ positions, which makes it almost like the GPS team tracking systems. In addition, the Next11 system includes an instrumented ball that tracks its position on the field and who has the ball, so teams have an accurate picture of ball possession and related stats. Here’s a breakdown of what they provide:
- Hardware: The system consists of 20 x player sensors in a charging case/station, 20 x calf sleeves, an instrumented ball with a charger, and the Edge (receiver) with a tripod.
- Connectivity/Apps: The sensors connect to the Edge (receiver) via a Bluetooth 5.0 Mesh Network and stream motion data and position data/signal in real-time. As this is a team solution, they have developed an iPhone/iPad app for coaches and managers which syncs all the data received by the Edge (receiver) via Bluetooth 5.0, so that they can manage their players. Next11 also developed an app for players to monitor their own performance.
- Metrics: Next11 presents the metrics in 3 main categories – Technical, Physical and Tactical. The ‘Technical‘ aspects include the number of (successful & unsuccessful) passes, passing stats (speed, direction, distance, relations/links) and ball possessions. The ‘Physical‘ aspects are simply the number of walks, runs, high-intensity runs, sprints, accelerations and decelerations. Lastly, the ‘Tactical‘ metrics include ball positions, player positions and interceptions. There is a mention of an ‘Intensity Indicator’ which is summing up the triaxial acceleration values. [It is essentially what Catapult coins as ‘Player Load‘ since they started.]
- Analytics: Through the metrics of every player, the system provides a profile of each individual player rating them according to their skills, technique, power, endurance, performance and development progress. It is also able to create a team profile (in the coach’s app) by analysing all the data and painting a bigger picture.
The Next11 system is only available for pre-order at the time of writing this and the estimated delivery is June 2022. It is also mentioned on their website that they will be launching with the Physical metrics/data only, and the Technical and Tactical metrics will be made available in Q3 of 2022 in addition to that, there is mention of a 4K camera integration in Q4 of 2022. Not quite sure what the camera integration will look like. The position tracking is an interesting one because they are relying on the Bluetooth 5.0 Mesh Network which is quite new and there has not been much reported about its accuracy. Besides the one-time hardware cost, users will be expected to pay a monthly subscription for Cloud access.
Feet Sensor 1: Jogo
Jogo is a startup based in the Netherlands. Their goal is to have a platform that improves (youth) football player development. They do this by collecting a player’s training and performance data on and off the pitch, interpreting that data and identifying areas where individual players can improve or where their strengths are. They also envision the platform to be accessible to scouts, so talented players can be identified should they choose to be. How are the performance data captured? This is by the means of insole sensors and video tracking/analytics. Here’s what they aim to provide:
- Hardware + Connectivity: 2 x insole sensors (one for each foot), Left and Right insoles that hold the sensors, magnetic charging cord for sensors. The sensors should connect with the Jogo app via Bluetooth. There isn’t any mention of real-time data so I presume the data is synced post-session.
- Sensor Metrics: As mentioned on their website and their Kickstarter campaign page, the insole sensors will provide the following metrics – Distance (Total, Dribbling, Running, Walking), Time on the ball, Ball touches, Ball received, Shot power, Passes, Leg distribution, Speed (Average, Sprint), Total sprints, Acceleration & Deceleration, Mechanical work, and Work rate.
- App/Video Analytics: Besides using the sensor, the Jogo app also uses camera tracking on the phone to track a variety of soccer and fitness workouts. It reminds me of other apps like Dribbleup or BALLN.
- Analytics/Coach Use: The analytics part of the app/platform is to take the data collected from the sensors and form a benchmark of the player. Then with subsequent sessions, the players’ progress can be tracked and coaches can also use the platform to assign specific exercises, monitor performance and give feedback.
A few things to note about Jogo since they first launched their Kickstarter campaign is, that firstly they have cancelled their Kickstarter campaign for their insole sensors due to some major changes within their company. Secondly (which is likely linked to the previous point), Jogo was acquired by 433 (the largest football social community globally) recently. What is known at this point is that the tech developed by Jogo will become part of 433’s platform. It may or may not be in the exact same form but it does appear that 433’s goal is to further engage football players (and fans) with tech, and Jogo did say that they intend to continue developing the sensors. So I guess we will see.
Feet Sensor 2: Xampion
Xampion is a startup that hails from Finland. They were founded in 2016 by a group called Progda which has experience in developing sensor hardware (IMU) and developing applications to analyse and visualise sensor data. Xampion’s feet sensor solution comes in the form of 2 insole sensors (with accompanying insoles) that tracks soccer motion in both feet. Here are more details of what they offer:
- Hardware + Connectivity: 2 x insole sensors (one for each foot), Left and Right insoles (that hold the sensors) designed in cooperation with orthopedical specialists of Respecta of the Ottobock Group, charging cable for sensors. The sensors connect with the Xampion App via Bluetooth. All sensor data captured during a game or training session is synced/downloaded post-session.
- Sensor Metrics: The metrics captured by the sensors include – Ball touches on each foot (number of strikes, passes, ball controls and others), Contact points (inside and outside the foot, and the tip of the foot), Speed of ball strikes, Movement data (acceleration, sprint speed, personal tempo, number of sprints, distance travelled) and Intensity levels.
- Analytics: Based on the data collected, the app calculates for each session, overall scores in five key Skill Points (Stamina, Movement, Control, Tempo and Activity). It also summarises for each session the count, quality and balance of the ball touchpoints.
- Coach Platform: Xampion also developed a web interface (Xampion Coach) for coaches to have a quick overview of all the players’ performance, compare sensor metrics in the various categories, set training goals for individual players, manage training plans and schedules, and evaluating training effectiveness.
At the time of writing/publishing this, the sensors can be purchased on their website and they ship to most European countries. They also work with a couple of online retailers outside of Europe including Australia, New Zealand and Japan. Purchasing the insole sensors come with a 12-months subscription for app and sensor firmware updates. After the 12 months, there would be a monthly subscription fee. The Coach web app also requires a subscription.
Feet Sensor 3: Playermaker
Playermaker was founded in Israel back in 2016/17. But even before the team at Playermaker developed the soccer sensor, they actually developed and launched other sensor products for sports. One of them was Motionize for kayaking. The Motionize sensor tracked paddling motion and gave real-time feedback on the kayaker’s technique. Subsequently, they wanted the sensor technology to have a greater impact in sports and so pivoted to soccer. What resulted was a pair of smart sensors designed to be strapped to the outside of a pair of soccer boots – one for the left boot and one for the right boot. Let’s see what their solution includes:
- Hardware + Connectivity: The Playermaker sensor kit (dubbed Uno) consists of 2 sensors (Left and Right), a carrying/charging case, USB-C charging cable, and 2 silicone straps that are also side specific (Left and Right). Like all the sensors covered above, these ones connect to the Playermaker app via Bluetooth and data can be synced/downloaded after each session.
- Sensor Metrics: Playermaker breaks down the metrics into 5 different categories. 1) Involvement – number of touches (contact with the ball), ball releases (kicks/shots/passes) and possessions (had control of the ball). 2) Playing Tempo – one-touches, short possessions (1.5secs or less), long possessions (>1.5secs). 3) Technical Balance – touch by leg (%), release by leg (%), receive by leg (%) and max kicking velocity. 4) Speed – max speed, sprints, accelerations/decelerations. 5) Volume – distance covered, sprint distance, work rate.
- Analytics & Tools: In terms of analytics, the app provides easy visualisation of the data, from the details to an overview of each session. It allows the player to benchmark their own performance with other elite players. Players can also set goals, track their progress over time, receive coach feedback and compare notes with peers and team mates.
- Team & Elite Tools: Teams and coaches can get access to a coaches dashboard where they can get an overview of the team’s physical and technical progress over time. Keep players engaged while monitoring their training schedule/load. For the elite players and teams, Playermaker provides a lot more tools on top of the coach dashboard including the ability for deeper analysis and video integration, further development of players, managing team performance and avoiding injuries.
Like many of the other products, Playermaker seems to have a focus on the youth soccer player market and semi-pro players who want to take their game to the next level. On the other hand, they have also been used by quite a number of professional clubs. The key difference in their product offerings is the apps/software and analytical tools/platform. Regardless of the player’s level, access to the Playermaker platform requires a monthly subscription which can be paid upfront for 12 months or 24 months. For teams wanting to order at least 10 units, they will have to contact Playermaker to find out more.
Summary & Final Thoughts
These are the soccer-specific sensors that I am aware of that are in the market or soon to be available. As mentioned, there are 2 main types of sensors: there are the ones worn on the calf and those worn at the feet. Even within each type of sensor, there are some variations in their solutions or additional features. What I have found is that all the soccer sensors will at least track the ‘Physical‘ and ‘Technical‘ metrics during a soccer game or training session. The general or most common ‘Physical Metrics‘ would include distances covered, speeds, sprints, and accelerations/decelerations. Then the general ‘Technical Metrics‘ will usually have the number of shots/kicks, the number of passes, touches/dribbling, speed of kicks and some possessions stats. Some of the products will have a little bit more metrics or different metrics and sometimes it is just a slightly different way of presenting them (e.g. number and percentage).
[ Interesting Fact: Every product originated from a different country (at least from what I have gathered)]
I just wanted to add 2 more thoughts before we end:
1/ Sensor Algorithms & Different Sensors: I think when it comes to tracking the ‘Physical Metrics’, the calculations or algorithms should be quite straightforward. Think about determining the number of steps, speed, acceleration/deceleration and distance. On the other hand, the ‘Technical Metrics’, might require identification algorithms applied to differentiate certain movements such as a ball touch, a kick, a pass or dribbling. My guess is that every sensor product will have its own proprietary approach to how they determine what combination of sensor signals means which movement. Especially since the sensors are placed/worn at different locations. It will be interesting to do a comparison of the different sensors (worn on one player) and compare the outcomes. I reckon there will be some differences.
But at the end of the day, it may not be so critical as to which sensor’s ‘Technical Metrics’ is more precise. If a player sticks to using one sensor for an extended period, they will be tracked consistently. This means they can use the benchmark values at the start and reliably monitor their own progress going forward. But if a player were to use one sensor for the first 6 months and then swap to another type or brand of the sensor for the next 6 months, they won’t be able to make a proper comparison.
2/ Additional Features that stand out: At a glance, some of the sensor products might look similar to another product. But on careful examination, the solution each one provides can be quite different from the next similar looking product. Beyond the basic differences (e.g. sensor metrics, or tracking of one leg vs both legs), there are three features that I thought really stand out.
Firstly, there is the Smart Ball from Next11. The Smart Ball basically has sensors and Bluetooth embedded within. It can report its position and which player it is closest to or in contact with. So when it comes to ‘ball possession metrics, I reckon having the Smart Ball will make it that much more accurate. Also, from a game analysis perspective, the position and speed of the Smart Ball can add some interesting context to the game.
Secondly, we have Real-time Tracking, which is also a feature in Next11. Real-time tracking of players allows coaches to see how hard each player has been going during a session and whether they should get them to rest before they run the risk of injury. This is a very common feature in the GPS trackers (that are worn in a vest). So I am a little surprised that it is not built into most of the soccer sensors listed above. I suspect adding an antenna to the sensor will make it too bulky to be worn in or on the soccer boot or even the back of the calf.
Thirdly, Video Tracking of Workouts. This is a feature from Jogo. The app uses the smartphone camera and pose estimation algorithms to track exercises or drills that can be done at a stationary spot in front of the camera. As mentioned, it is similar to other soccer apps like DribbleUp or BALLN (previously known as Get Metrix). I think there is value to tracking individual workouts this way because there is accountability, and players/coaches can easily quantify these workouts and see how they translate to field performance.
Finally, the application of sensors in soccer in this form has actually been around for a little while (Footbar was founded in 2014). But it only really became more widely known and used in the last 3-4 years. Unfortunately, it already looks like one of the products (Zepp) might not be continuing. But we are confident that the solutions and features will keep evolving as more players and teams have used them for an extended period and product developers learn from those experiences. It will be an interesting area to keep an eye on. If you would like to follow what else could happen in this space, remember to subscribe to our blog here: link. If you would like more information about any of the above, or you have some sports tech ideas you would like to chat to someone about, feel free to reach out or leave a comment below. As always, thanks for reading!