Comparative analysis of recording system for collecting kinematic data in beach volleyball

The monitoring and assessment of athletes' behavior by Electronic Performance and Tracking Systems (EPTS) is a growing reality. However, the reliability and precision of the recording systems remains unclear. The aim of this study was to compare the differences between Global Navigation Satellite System (GNSS) and Local Position Systems (LPS) based on Ultra-Wide Band (UWB) in terms of kinematic measurements. Twelve beach volleyball matches were recorded in a tournament, leading to a total of 469 rallies performed. Kinematic variables such as distance (total, explosive, and speed area), accelerations, decelerations, and speed (mean and maximum) were measured with GNSS and UWB systems. Mean-difference tests (T-test or Mann-Whitney U test) were applied to calculate the dissimilarity between systems (p < 0.05), as well as the effect size at 95% confidence intervals. Statistically significant differences were found in distance, explosive distance, running at 0-6 and 6-12 km/h, and total number of accelerations and decelerations favoring the GNSS system, with large and very large differences in the last two variables. Contrarily, a statistically significant difference was observed in maximum accelerations favoring the UWB system, with a moderate difference. These findings reveal strong divergence between both systems in the measurement of key kinematic variables, so data should be analyzed taking into consideration the standardization derived from the system used.