Age-related associations in worst-case-scenario running performance among Chinese Super League football players

Abstract Background Worst-case-scenario (WCS) analysis characterises short passages with the highest external locomotor demands. Age-related associations in WCS running performance among professional male football players in the Chinese Super League remain insufficiently described. Methods This retrospective observational study included 11,956 player-match observations from 1,030 Chinese Super League matches played during the 2017–2021 seasons. Twelve outcomes were derived from high-intensity-running-distance-defined 1-, 3- and 5-min rolling windows. Poisson generalised linear mixed models adjusted for match location, relative team ranking and match outcome, and included a player random intercept. Results In the pooled sample, the simulation-based reporting rule retained quadratic turning points for 1-min high-intensity running distance and high-intensity efforts at 25.1 and 25.3 years, respectively. Position-stratified models retained turning points for 8 of 60 position-outcome combinations, ranging from 25.9 to 28.7 years. Remaining outcomes were summarised using fitted linear contrasts, with negative estimates tending to be larger for longer windows; no age by window-duration interaction was fitted. Conclusions Because positions were modelled separately, positional patterns are descriptive rather than formal between-position contrasts. Turning-point uncertainty was based on an approximate coefficient-based simulation and should not be interpreted as an exact biological threshold. These cross-sectional estimates cannot establish within-player ageing and should not be used alone to prescribe training loads or player deployment.