Relationships between heart rate-based training load and running metrics in field hockey players

BACKGROUND: Monitoring training load (TL) is essential for optimizing performance and reducing injury risk in team-sport athletes; however, how internal, and external load interact across different competition contexts remains unclear in elite field hockey. This study aimed to examine the structure of GPS-derived running metrics and their associations with heart rate (HR) -based internal TL during simulated and international competitions in elite female field hockey players. METHODS: Individual data recordings from 18 female field hockey players during 13 simulated competitions and 8 international competitions were analyzed, with HR-based internal TL calculated from heart rate data and GPS-derived running metrics used to examine load structure and associations. RESULTS: Exploratory factor analysis identified two running load factors, with PA1 component comprising total distance covered, duration, total player load, sprint effort, decelerations, and accelerations and PA2 component comprising high-speed distance, maximal speed, sprint distance, and relative distance, together explaining 70.4% of the total variance. Linear mixed-effects models showed that PA1 (Δ=0.42) and HR-based internal TL(Δ=1.35) were significantly higher during international competitions than simulated competitions, whereas PA2 did not differ between conditions. HR-based internal TL was positively associated with both PA1 (β=0.031) and PA2 (β=0.019); however, this association was moderated by competition conditions only for PA1, with a stronger coupling observed during international competitions. CONCLUSIONS: These findings demonstrate that the relationship between GPS-derived external load and HR-based internal load varies by competition context, emphasizing the need for context-specific TL monitoring.