Abstract
Previous research, although limited, suggests that both hypoxia and bed rest influence psychological responses by exaggerating negative psychological responses and attenuating positive emotions. The present study investigated the effect of a 21-day prolonged exposure to normobaric hypoxia and bed rest on affective responses and fatigue. Eleven healthy participants underwent three 21-day interventions using a cross-over design: (1) normobaric hypoxic ambulatory confinement (HAMB), (2) normobaric hypoxic bed rest (HBR) and (3) normoxic bed rest (NBR). Affective and fatigue responses were investigated using the Activation Deactivation Adjective Check List, and the Multidimensional Fatigue Inventory, which were completed before (Pre), during (Day 7, Day 14, and Day 21) and after (Post) the interventions. The most negative psychological profile appeared during the HBR intervention. Specifically, tiredness, tension, general and physical fatigue significantly increased on days 7, 14, and 21, as well as at Post. After the HBR intervention, general and physical fatigue remained higher compared to Pre values. Additionally, a deterioration of psychological responses was also noted following HAMB and NBR. In particular, both hypoxia and BR per se induced subjective fatigue and negative affective responses. BR seems to exert a moderate negative effect on the sensation of fatigue, whereas exercise attenuates the negative effects of hypoxia as noted during the HAMB condition. In conclusion, our data suggest that the addition of hypoxia to bed rest-induced inactivity significantly worsens affective responses and feeling of fatigue.
Highlights
It is envisaged that future long-term space explorations will establish permanent habitats on the Moon and Mars
While the resting Heart rate (HR) remained stable across all interventions, it was significantly higher during both hypoxic conditions (HAMB: 68 ± 3 beats·min−1; hypoxic bed rest (HBR): 72 ± 2 beats·min−1) than during normoxic bed rest (NBR) (60 ± 2 beats·min−1; p < 0.05)
Our results suggest that combined hypoxia and bed rest (BR)-induced unloading (HBR) exert a detrimental effect on affective and fatigue responses as compared to the independent effects of hypoxia (HAMB) and BR (NBR)
Summary
It is envisaged that future long-term space explorations will establish permanent habitats on the Moon and Mars. To minimize the risk of decompression sickness (DCS) of astronauts preparing for extravehicular activities, these habitats will be hypobaric and hypoxic (Bodkin et al, 2006). Hypoxic Inactivity and Fatigue a slow decompression lasting several hours, and breathe oxygen, to enhance nitrogen elimination from the body, minimizing the etiology of venous gas emboli, and the risk of DCS. Whereas EVAs are not frequent events on the ISS, they will undoubtedly be conducted on a daily basis during missions on the Moon and Mars. By maintaining the ambient pressure in future habitats at the same pressure as the space suits, but with a higher fraction of oxygen, the need for decompression will be eliminated
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