From stadium to training ground: Advancing monitoring metrics in GNSS technology, peak locomotive demands, and deceleration loads in professional soccer

Abstract

Despite the widespread adoption of Global Navigation Satellite Systems (GNSS) in professional soccer, significant challenges persist in ensuring measurement accuracy across different playing contexts. These limitations are particularly evident in stadium environments where structural interference can compromise signal quality, and in the methodological disconnect between training and match monitoring approaches. Furthermore, while deceleration actions represent significant physiological loading, current monitoring practices do not prioritise deceleration loads to the same extent as other locomotor metrics, limiting their integration into applied load management strategies. This thesis aimed to enhance both theoretical understanding and practical application of load monitoring in professional soccer through four progressive studies. The first study established a novel methodology for assessing GNSS signal quality in stadium environments, revealing position-specific disparities. The second study validated contemporary GNSS technology, demonstrating improved accuracy in challenging conditions. The third study examined position-specific peak locomotor demands, while the fourth investigated deceleration load and fatigue responses in training. Data were collected across multiple competitive seasons in the English Premier League and English Second Division (Championship), incorporating multiple stadium environments and training contexts. The first study revealed that wide-positioned players experienced nearly double the signal disruptions compared to central players during matches in stadia (16.5% ± 13.9% vs. 8.4% ± 11.1%, p<0.01). This study also established a novel method for practitioners to identify and account for periods of compromised signal quality in applied settings. The second study validated contemporary GNSS technology, demonstrating improved validity in challenging stadium environments (1.2% underestimation compared to 2.9% with previous technology). Building upon these methodological advances, the third study analysed position-specific peak locomotor demands using rigorous quality control measures, challenging existing assumptions by revealing no positional differences in peak high-speed running demands in match play. The final study examined the relationship between deceleration loads and fatigue responses specifically in the training environment, revealing that traditional fatigue monitoring measures validated in match play, such as flight time and contraction time ratio, may not effectively capture training-induced responses. This study systematically established the importance of context-specific monitoring approaches while identifying optimal methods for quantifying deceleration load to capture the dose-response relationship in training. The findings from this thesis have significant implications for load monitoring in professional soccer, establishing new methodological standards while providing evidence-based frameworks for practitioners. The outcomes of this research demonstrate the critical importance of signal quality assessment in stadium environments, where wide-positioned players experienced nearly double the signal disruptions compared to central players during matches. This research challenges existing assumptions about position-specific demands by revealing no positional differences in peak high-speed running demands in match play when applying rigorous signal quality controls, contrary to previous studies reporting higher demands for wide positions. Furthermore, this work provides novel insights into training-specific fatigue monitoring by identifying that low-intensity deceleration thresholds (<-1 m·s⁻² and >20% of maximum) showed stronger associations with post-training fatigue than traditional high-intensity thresholds, and that eccentric duration and peak power during countermovement jumps were the most sensitive indicators of deceleration-induced fatigue. These advances have the potential to enhance practitioners' ability to effectively monitor and manage player loads while establishing new standards for measurement validity in applied sports science research.