At altitude, humans are exposed to environmental hypoxia induced by the decrease in barometric pressure. On duty or in training, mountain troops, paratroopers or aircrew are regularly exposed to altitude. The effects of altitude on humans occur gradually from 1500 m and depend on both the duration of exposure and the altitude level. Cognitive disorders can occur from 3500 m (threshold of disorders) but there is a very large inter-individual variability. The countermeasure to altitude hypoxia is oxygen but its use is not systematic between 3000 and 4000 m. Its use depends on the duration of exposure, without clearly established standards. Incapacitating effects on the operational capacity and health of soldiers can therefore occur as early as 3500 m. In operations or during training, altitude exposure is often associated with a significant sleep debt (particularly during night or early morning missions), jet lag or precarious rest conditions in overseas operations. These sleep restrictions promote the degradation of mental performance with effects similar to those observed in hypoxia. The combination of these constraints induces a physiological stress which can favour alterations in mental performance, an increase in incapacity, intolerance to altitude or the occurrence of altitude-related pathologies in military personnel. This could occur in particular in the operational zone around the threshold of disorders (3500 m) where the indication of oxygen is discussed. The objective of this study is to assess the impact of acute sleep restriction on hypoxia tolerance.