Early adaptation to high-altitude: Mood and cognitive responses at simulated 4500 m.

High-altitude exposure induces hypoxemia, triggering metabolic adjustments to enhance oxygen delivery. This acclimatization process often involves mood changes, cognitive alterations, and Acute Mountain Sickness (AMS) symptoms. This study examined the effects of simulated hypoxia at 4500 m on physiological variables, reaction time, lapses, and mood states. Twenty-three volunteers were exposed to a simulated 4500 m altitude for 4 h in a normobaric hypoxia chamber. Lactate, glucose, SpO2, heart rate (HR), and AMS symptoms were assessed before and every hour during exposure. As expected, SpO2 significantly decreased (p < 0.001), while HR increased (p = 0.006) during exposure. Reaction time remained unaffected, but lapses significantly correlated with lactate levels (p = 0.002). Mood states, particularly tension (p = 0.001) and fatigue (p < 0.001), were associated with AMS symptoms. Simulated high-altitude exposure induced physiological alterations, including decreased SpO2, increased HR, and a significant correlation between lactate levels and cognitive performance. While reaction time was unchanged, mood disturbances were strongly related to AMS. These findings highlight the need for strategies to mitigate both physiological and psychological effects of hypoxia.