Human physiological and metabolic responses to an attempted winter crossing of Antarctica: the effects of prolonged hypobaric hypoxia.

Abstract

An insufficient supply of oxygen to the tissues (hypoxia), as is experienced upon high‐altitude exposure, elicits physiological acclimatization mechanisms alongside metabolic remodeling. Details of the integrative adaptive processes in response to chronic hypobaric hypoxic exposure remain to be sufficiently investigated. In this small applied field study, subjects (n = 5, male, age 28–54 years) undertook a 40 week Antarctica expedition in the winter months, which included 24 weeks residing above 2500 m. Measurements taken pre‐ and postexpedition revealed alterations to glucose and fatty acid resonances within the serum metabolic profile, a 7.8 (±3.6)% increase in respiratory exchange ratio measured during incremental exercise (area under curve, P > 0.01, mean ± SD) and a 2.1(±0.8) % decrease in fat tissue (P < 0.05) postexpedition. This was accompanied by an 11.6 (±1.9) % increase (P > 0.001) in VO2 max corrected to % lean mass postexpedition. In addition, spine bone mineral density and lung function measures were identified as novel parameters of interest. This study provides, an in‐depth characterization of the responses to chronic hypobaric hypoxic exposure in one of the most hostile environments on Earth.

A comparison of the metabolic effects of sustained strenuous activity in polar environments on men and women

“…From earlier expeditionary studies the measured energy expenditure was found to be much higher than that predicted from activity scores 14 and a 60% increase was found in the BMR 15 which was attributed to increased thyroid activity. This increase in BMR is consistent with small levels of weight loss seen in men undertaking low levels of physical work whilst over-wintering in Antarctica 16 . In a recent analysis of energy expenditure and substrate utilisation on an all-male transantarctic expedition (Spear-17), we found that this 60% increase in BMR was consistent with an increase in the energy required for thermoregulation 17 .…”

Can Hypoxic Conditioning Improve Bone Metabolism? A Systematic Review

“…Cyclic protocols adopted a pattern of exposure to hypoxia followed by the same time course of exposure to normoxia, lasting 4 [63] and 5 h [64] per day. Six out of the ten studies in humans, included in this review, analysed the effect of sustained or cyclic hypoxia in healthy active [60,61,62,65,66] or sedentary adults [67]. Three studies [60,61,62] implemented sustained HC corresponding to periods of 16, 24 and 60 weeks.…”

“Take My Bone Away?” Hypoxia and bone: A narrative review

“…Hitherto, this review has mostly examined the molecular response of bone cells to hypoxia. However, it is also pertinent to inspect the responses from the available in vivo studies (for a more compre- Long-term sustained exposure has been reported to reduce several indices of bone health (Basu et al, 2013(Basu et al, , 2014O'Brien et al, 2018;W. Wang et al, 2017) whereas shorter term sustained exposure appears less noticeable (Rittweger et al, 2016) (2013) monitored members of the Indian army exposed to real altitudes of 5,400 to 6,700 m over 4 months and W. Wang et al (2017) exposed rats to a simulated~6,000 m for 21 days.…”

“…Long‐term sustained exposure has been reported to reduce several indices of bone health (Basu et al, 2013, 2014; O'Brien et al, 2018; W. Wang et al, 2017) whereas shorter term sustained exposure appears less noticeable (Rittweger et al, 2016). Bone's varied response to hypoxia may be a function of the oxygen concentration it receives.…”