Competing at sea level reduces high-intensity match running performance in elite U20 soccer players chronically training at moderate altitude

Elite soccer players increasingly live and train at moderate altitude, while inter-regional competition across different altitudes has become more frequent. However, evidence regarding whether transitioning from moderate altitude to sea-level competition influences match running performance remains limited. Twenty-three elite U20 male outfield players from a professional soccer club based at moderate altitude were monitored during friendly matches played at moderate altitude and sea level. Running performance was quantified using 10-Hz GPS devices, from which the following variables were derived: distance per minute (DPM), top speed (TS), high-speed running distance (HSR), sprint distance (SprintD), explosive accelerations (EAcc), and explosive decelerations (EDec). Generalized linear mixed models were used to examine the effect of competition altitude, with player names included as a random effect. Results showed that HSR (mean change; −32%; ES: −1.11), SprintD (−24%; −0.54), EAcc (−30%; −1.04), and EDec (−39%; −1.23) were substantially lower during matches played at sea level than during matches played at moderate altitude. These findings indicate that competing at sea level substantially influences match running performance in elite U20 male soccer players chronically trained at moderate altitude, particularly reducing high-intensity and explosive actions.