The psychological impacts of extreme situations are a great concern and have become an issue of major importance for performance, well-being and the outcome of missions (Kanas, 1998). A situation is considered as extreme when an individual is subjected to exceptional physical or psychosocial circumstances demanding adaptive responses which could overwhelm its physiological and psychological resources (Rivolier, 1992). Thus, extreme situations represent unfamiliar conditions (risks, hazards, and ultimately death) confronting persons with their limits and consequently with their adaptive capacities. Extreme situations are for example extreme sports, long-duration spaceflights, wintering in polar stations or polar expeditions, submarine missions, solitary navigation, deep diving, very high terrestrial altitude, and military missions.