Associations between weekly training load, match load, and next-day neuromuscular function in elite football players: a longitudinal observational study

This longitudinal observational study examined associations between accumulated weekly training load, match load and next-day muscle-specific force in elite male football players. Routine monitoring provided 139 player-week observations from 24 outfield players across 15 non-consecutive microcycles. GPS-derived training and match metrics were summarized using separate principal component analyses. Nordic eccentric hamstring, prone isometric hamstring, and hip adductor and abductor mean force were assessed 12–18 h after matches, with bilateral values averaged. Nineteen players contributed observed force measurements; five had no force measurements in the included microcycles. Missing outcome values (18.0–30.9%) were handled using 50 two-level predictive-mean-matching imputations. Random-intercept models were fitted separately to each completed dataset and pooled. Higher match PC1 had a negative association estimate for Nordic force (β = − 9.39 N per SD; model-based 95% CI − 19.44 to 0.66; p = 0.067). The player-cluster-robust interval was wider (− 25.31 to 6.53 N; p = 0.211). All 12 retained load-force associations had confidence intervals spanning zero under both approaches. The results did not establish the hypothesized association between higher match load and lower next-day Nordic force. Missing force measurements, limited cluster numbers and unmeasured contextual factors constrain interpretation. These data do not establish individual fatigue or injury-risk thresholds.