Inter-System Agreement and Reliability of a Gnss-Rtk and Dual-Imu Wearable System for Soccer Performance Monitoring

<title>Abstract</title> <p>Purpose This study evaluated the inter-system agreement and interunit reliability of a GNSS real-time kinematic (GNSS-RTK) and dual-inertial measurement unit (IMU) wearable system during soccer-specific activities using a commercially available 10-Hz GNSS device as a field-based comparison system. Methods Thirty trained male team-sport athletes completed sport-specific drills, simulated match activities, and competitive match-play scenarios while simultaneously wearing the GNSS-RTK/dual-IMU system and a 10-Hz GNSS device. External-load variables included total distance, peak speed, and distance covered within predefined speed zones. Inter-system agreement was assessed using paired-samples t-tests, Pearson correlation coefficients, and Bland-Altman analysis. Interunit reliability was evaluated using intraclass correlation coefficients (ICC) and percentage typical error of measurement (%TEM). Results No significant differences were observed between systems for any external-load variable (p &gt; 0.05). Strong correlations were identified for total distance (r = 0.89), peak speed (r = 0.84), and high-speed running distance (r = 0.81), whereas agreement was substantially lower for very high-speed running (VHSR) distance (r = 0.65). Bland-Altman analysis demonstrated small mean biases for total distance (− 6 m), peak speed (+ 0.08 km·h⁻¹), and low-speed running distance (− 8 m). Interunit reliability of the GNSS-RTK system was good to excellent across most variables (ICC = 0.80–0.96). The lowest measurement error was observed for low-speed and time-based variables, whereas VHSR-related metrics demonstrated considerably greater variability (%TEM = 11.2–13.2%). Conclusions The GNSS-RTK and dual-IMU wearable system demonstrated acceptable inter-system agreement and good-to-excellent interunit reliability for several key external-load variables in soccer. Agreement was strongest for cumulative locomotor metrics such as total distance and peak speed, whereas VHSR metrics exhibited lower agreement and greater measurement variability. These findings support the practical application of GNSS-RTK technology for monitoring external load in soccer, provided that high-intensity running metrics are interpreted with appropriate caution.</p>