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The sensing unit xG-1 enhances sports coaching by providing real-time analysis of the players' movements in team sports. The researchers developing this technology published a study in English in the Journal of Digital Life, a multidisciplinary online journal focusing on digital technology.
Why Data-Driven Training?
In the 2023 Rugby World Cup in France, Japan faced defeat by Argentina on October 8, falling short of advancing to the knock-out stage. Nevertheless, the players' resilience left a lasting impression on spectators. On the same day, President Masato Tsuchida of the Japan Rugby Football Union commended the players for their efforts on the union's website. He affirmed the team's commitment to "reach the top" in future Rugby World Cups. On October 11, Tsuchida announced that he would be selecting the next head coach, emphasizing the goal of recruiting and developing players, including high school and college students.
A data-driven approach is crucial in all sports coaching, including rugby. This methodology shifts the focus from traditional subjective coaching methods to relying on objective data for player assessments and team decisions. To implement this approach, some teams, particularly those abroad, provide sensing units to their players. These track the players' positions and behavior during games, providing valuable data for coaching purposes.
Despite the availability of such devices, their limited functionality for in-depth analysis of the player's condition and the lack of customization have hindered widespread use. The developers of xG-1 conducted a survey to address these issues.
The survey revealed that coaches wanted more features including a dashboard that indicates the timing of player substitutions and a function that compares exercise intensity. In response, the researchers developed a sensing unit that tracks the players in detail. They also developed software that offers in-depth analysis of the collected data. Using this technology, coaches would be able to understand the players' condition during matches and also assess their growth and condition during practice.
Enhancing Accuracy
xG-1 is a compact device, measuring only 88 mm x 44 mm x 19 mm and weighing 64 g. During matches or training sessions, this device can be conveniently placed in a pocket on the back of a vest worn beneath the uniform.
To ascertain a player's position, the system utilizes a Global Navigation Satellite System (GNSS). It is compatible with both the American Global Positioning System (GPS) and the Japanese Quasi-Zenith Satellite System "Michibiki."
However, relying on a single receiver, like those found in car navigation systems or smartphones, results in substantial errors. To address this, the researchers implemented real-time kinematic positioning. This employs multiple receivers to compensate for common errors in positional information. Consequently, the researchers achieved a margin of error of only a few centimeters when the player was stationary and a few tens of centimeters when the player was running.
Furthermore, xG-1 measures the players' posture, in terms of forward/backward, up/down, and left/right tilt. The device also has acceleration sensors that track the number of times and the distance at which the player moved at a "sprint (over 24 km/h)" or at "high-speed (over 18 km/h)." It also provides information that cannot be ascertained from videos, such as heart rate and impact strength from collisions with opponents. Falls and jumps can also be analyzed using the sensor values.
Crucially, xG-1 has secured FIFA's Electronic Performance and Tracking Systems (EPTS) certification and a World Rugby certification. This means the device can be worn during official games in these sports.
Player Substitutions
The research team also developed software designed to assist coaches in visualizing the extensive data collected by xG-1. Particularly notable is the number of features available on the dashboard. First, the "field function" allows coaches to confirm the player's positioning. Second, the "panel function" graphs the player's running distances and heart rates. Third, the "exercise intensity analysis function" analyzes the player's exercise over a specified period, such as a week. Finally, the "exercise intensity comparison function" compares the current team's exercise intensity with the team's past data or data of top athletes.
These four functions support coaching using a data-driven approach. For example, a soccer coach could use the "panel function" to decide when to substitute players. The function indicates when a player's heart rate or running distance exceeds a predetermined threshold. Additionally, the "exercise intensity analysis function" calculates the injury risk indicator Chronicle Workload Ratio (ACWR) based on the player's typical practice volume. This helps coaches decide whether a player should undergo rigorous training or rest in preparation for a crucial match. Furthermore, the system's "station screen" can also produce a heatmap in Excel or PDF format indicating the movement patterns of players.
Discovering and Developing Players
The research team distributed xG-1 to more than 50 sports teams. Notably, how a team used the device varied depending on whether they were a professional, college, or high school team.
The leading team of the J1 League utilized xG-1 to analyze players' acceleration and deceleration patterns and review game outcomes. Furthermore, medical coaches employed the collected data to facilitate the rehabilitation of players recovering from injuries.
At the collegiate level, xG-1 played a role in assessing training quality and adjusting training content. In high school teams, players used the data to determine their optimal positions during games. The system garnered high praise from all teams that integrated it into their training programs.
Based on these outcomes, the researchers underscored that xG-1 stands out as a highly accurate system, capable of measuring individual player movements and analyzing the overall team formation. They proposed that the system may be useful in discovering and nurturing young athletes. A member of the research team suggested that xG-1 could be used to "provide tactical analysis and assistance in planning training menus to advisory teachers of elementary, junior high, and high school club activities who are not professional sports coaches."
Research Team Members
Takayuki Yamada, Hidekazu Masaki, and Yutaka Matsubayashi of xSENSING Co., Ltd., Professor Shigenori Tanaka, Specially Appointed Professor Takeshi Naruo, and Assistant Professor Yuhei Yamamoto of Kansai University, Professor Ryuichi Imai of Hosei University, Professor Kenji Nakamura of Osaka University of Economics, Associate Professor Wenyuan Jiang of Osaka Sangyo University, and Chihiro Tanaka, formerly of Kansai University.
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This article was first published on iza! by the Journal of Digital Life. Read a related article in Japanese.
Author: Taketoshi Noma
