Effects of transitions between moderate altitude and sea level on running performance during training in U20 elite male soccer players

This study aimed to quantify changes in running performance-related parameters in U20 elite male soccer players across transitions between training at moderate-altitude and sea level. Nineteen players from a professional club were monitored across three stages: moderate altitude (2000 m), sea level (<500 m), and return to moderate altitude. Running performance was assessed using 10-Hz GPS, and generalized linear mixed models were applied with altitude stage as a fixed effect and player as a random effect. Results showed substantial reductions in distance per minute (DPM: mean change in percent; ±90% confidence intervals; −9%; ±3%), high-speed running distance (HSR: −55%; ±16%), sprint distance (SprintD: −78%; ±30%), explosive accelerations (EAcc: −32%; ±7%), and explosive decelerations (EDec: −29%; ±8%) from the first stage (moderate altitude) to the second stage (sea level). By contrast, DPM (7%; ±4%), HSR (60%; ±14%), SprintD (81%; ±28%), EAcc (28%; ±8%), and EDec (29%; ±8%) increased substantially when returning from the second stage (sea level) to the third stage (moderate altitude). These findings indicate that transitions between moderate altitude and sea level induce marked but reversible changes in training running performance, particularly in high-intensity actions. The results highlight the context-specific nature of altitude-related adaptations and may inform training load management in elite youth soccer.