Effects of Flag Carriage on Running Performance, Physiological Responses, and Repeated-Sprint Ability in Soccer Assistant Referees

Referees and assistant referees play a central role in enforcing the Laws of the Game during matches. The main referee holds ultimate responsibility, while assistant referees monitor offside situations, signal fouls outside the referee’s line of sight, and assist with decisions on corner kicks, free kicks, and other restarts. Throughout the match, assistant referees use short flags to communicate standardized signals to the referee, making effective coordination essential for accurate match management. This study used a crossover design to examine the effect of flag use on repeated-sprint performance among 37 soccer assistant referees (19 Premier League and 18 National League) in Israel, assessed using a modified change-of-direction (CODA) protocol. The evaluated measures included total sprint time (TST), ideal time, percentage decrement in performance (PD), average heart rate, and subjective rating of perceived exertion (RPE). Statistical analysis revealed significant differences between conditions. Performance was better without the flag in both total sprint time (p < 0.05, d = 0.55) and ideal time (p < 0.05, d = 0.62). The percentage decrement was higher in the no-flag condition (p < 0.05). Higher heart rate (p < 0.05, d = 1.49) and higher RPE (p < 0.01) were also recorded. These findings suggest that flag carriage may constrain sprint performance during repeated change-of-direction tasks and should be considered in the physical testing and preparation of soccer assistant referees.