Associations Between GPS-Derived External Match Load and Refereeing Performance in Elite Football Referees

This study examined associations between GPS-derived external match-load variables and official refereeing performance in elite football referees. The cohort comprised all 17 main referees eligible to officiate in the highest Croatian national competition during the 2022/2023 season, including 10 UEFA/FIFA-listed referees. One referee was excluded from the field analysis because of injury, leaving 84 official-match observations from 16 referees. Refereeing performance was based on confidential official match grades additionally reviewed by seven experts appointed by the Croatian Football Federation Referees Committee. Because repeated matches were nested within referees, the primary analysis used referee fixed-effects models with referee-clustered standard errors and exact wild cluster bootstrap inference. Holm correction was applied across six GPS variables. The match-level grade was 8.27 ± 0.25 (range 7.30–8.50). Deceleration count showed a positive within-referee association with grade (B = 0.0068, 95% exact wild-cluster-bootstrap CI = 0.0036 to 0.0093, exact bootstrap p = 0.006, Holm-adjusted p = 0.038). Total distance, high-intensity running distance, sprint count, acceleration count, and maximum speed were not significant after correction. Sensitivity analyses showed that some estimates depended on model specification. GPS variables should therefore be interpreted as measures of match demands, not as direct measures of refereeing quality.