Arctic and Antarctic regions are still the most extreme environments for humans to live in. They combine geographical and social isolation, sensory deprivation, as well as extremely cold ambient temperatures, and an altered circadian rhythm. As human presence in these regions becomes more frequent due to the exploitation of natural resources or touristic and athletic endeavors, knowledge about physiological changes occurring under their influence becomes more important. Investigation of long-term stays in the German Antarctic research station reveal changes in body composition, circadian rhythm, as well as hormonal and metabolic changes in the overwinterers. Analysis of physiological changes in participants of the ultraendurance race “Yukon Arctic Ultra” in northern Canada show significant changes in energy expenditure, body composition, as well as sleep and heart rate variability.
