Micro-interval fatigue dynamics and repetitive sprint performance: a time-series model of adaptive pacing in Thai professional soccer

Introduction: Professional soccer involves intermittent high-intensity demands that require players to regulate effort throughout prolonged match play. Although Global Positioning System (GPS) technology has enhanced external workload monitoring, fatigue is still often examined using coarse temporal approaches that overlook short-term fluctuations and adaptive pacing, particularly in tropical competitive environments. Objective: This study examined micro-interval fatigue dynamics and adaptive pacing behaviour in professional Thai soccer, focusing on temporal workload decay patterns and the moderating role of Repetitive Sprint Ability (RSA). Methodology: A longitudinal observational design was applied using GPS-derived match data from professional players competing under tropical conditions. External workload was segmented into fine-grained temporal intervals, and time-series regression was used to analyse workload decline and RSA contribution across match phases. Results: Workload exhibited a non-linear pattern, with brief post-half-time reinvestment followed by an abrupt late-match decline identified as a Critical Fatigue Point (CFP). Match time was the primary factor associated with workload reduction, while RSA moderated the rate of decline. Discussion: Findings indicate that fatigue is strategically regulated rather than uniformly progressive. Conclusions: Micro-interval time-series analysis supports time-specific and individualized workload management in professional soccer under tropical conditions.