Cortisol, testosterone and body composition changes during overwintering at Concordia in Antarctica

Concordia in Antarctica is one of the most remote and inhospitable inhabited places on the planet. Overwintering at Concordia presents extreme environmental conditions combining both physiological stress [three-month-long period of polar night (early May to early August) and three-month period of polar day (early November to early February), severe cold, and high-altitude hypoxia] and conditions of isolation and confinement known to induce both physical and cognitive alterations. However, given the very small number of subjects experiencing such conditions, literature remains scarce on the real impact of an overwintering period on steroid hormone changes. Using monthly records, we therefore assessed the impact of an overwintering in 23 male participants on awakening and evening concentrations of cortisol and testosterone, body composition and physical aptitude assessed using a Chester submaximal test. Across overwintering, 10 of the 23 subjects (Group 1) lost more than 2 % of their muscle mass. Awakening and evening concentrations of cortisol and testosterone were preserved throughout wintering with no significant deterioration in physical aptitude. However, Group 1 vs. Group 2 participants had higher end-exercise heart rate and lower testosterone fluctuations between awakening and evening (p < 0.05). These results highlighted the great adaptation of the hypothalamic-pituitary-adrenal and gonadal axis functions to long-term extreme polar exposure. Further studies are needed to determine the mechanisms underlying the alteration in muscle mass occurring in almost half of the winterers, taking into account the subjects' energy intake and expenditure as well as their initial physical aptitude, in order to propose effective diet and physical activity countermeasures.