Preacclimatization

Preacclimatization is a preparatory process intended to provoke adaptive physiological responses before an anticipated exposure to environmental stress. The aim is to reduce the risk of adverse symptoms and to preserve or enhance performance, tolerance, and safety when the person encounters conditions such as high altitude, extreme heat or cold, or hypoxic environments.

Common approaches include intermittent or simulated exposure to the stressor, such as intermittent hypoxia delivered via altitude tents, hypoxic masks, or controlled normobaric/hypobaric conditions, and structured heat or cold exposure programs. Protocols typically run from several days to several weeks and may combine exposure with physical training. Some regimens use multistage ascent schedules or combined acclimation strategies like intermittent exposure followed by real environment exposure.

Evidence indicates that preacclimatization can partly reduce acute adverse effects, shorten the time needed to adapt, and support performance under challenging conditions, but results are heterogeneous across individuals and protocols. Safety considerations include monitoring hydration, core temperature, electrolyte balance, and signs of overexertion or heat illness; professional supervision is advised for structured programs.

Preacclimatization is distinct from acclimatization, which describes adaptive changes during actual exposure to the stressor. It is used in military, athletic, aviation, and expedition contexts to prepare for high altitude, hot or cold environments, or other extreme conditions.