Normobaric hypoxia training as acclimation for elite footballers competing at altitude: A case report from the Chilean National Team.

Competing at high altitude (HA) poses major physiological challenges for sea-level athletes and can markedly impair performance. Normobaric hypoxia has emerged as a practical training and acclimation strategy, yet real-world evidence in elite sports remains limited. We report the preparation of the Chilean men's national football team ahead of a World Cup qualifying match in El Alto, Bolivia (4150 m.a.s.l.). Thirteen players completed 4-10 normobaric hypoxia sessions simulating altitudes of 3250-4480 m.a.s.l. Physiological responses were evaluated, and performance at HA was compared with that at sea-level. SpO2 remained stable during sessions 1-4 followed by progressive increases in sessions 5-6. Mixed-effects modeling identified an association between session number and SpO2 with effects independently influenced by exercise type, simulated altitude, and number of sessions completed. Although the acclimation protocol improved physiological responses, it did not fully offset the demands of HA, and high-speed running per minute (HSR/min) and average speed (m/min) remained lower at HA than at sea level. This case report describes the implementation of short-term normobaric hypoxia training in elite football and suggests potential benefits for acclimation. The heterogeneous responses observed highlight the importance of individualized monitoring to optimize performance at altitude.