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.
Highlights
At high altitudes, the inspired partial pressure of oxygen (O2) is decreased as barometric pressure (PB) falls, leading to hypobaric hypoxia
An increase in blood lactate is observed upon acute hypoxic exposure both at rest (Siervo et al 2014) and in response to submaximal exercise (Sutton et al 1988), a response likely linked to hypoxic inducible factor-1a (HIF-1a)-dependent upregulation of glycolytic metabolism (Semenza et al 1994; Behrooz and Ismail-Beigi 1999; Semenza 1999; Lopez-Barneo et al 2001)
Bone mineral density (BMD), bone mineral density; FVC, forced vital capacity; FEV1,forced expiratory volume in 1 sec, bpm, beats per minute, sBP, systolic blood pressure, dBP, diastolic blood pressure, mean arterial pressure (MAP), mean arterial blood pressure. n = 4–5, values presented as mean Æ SD. 1Denotes significance, P < 0.05
Summary
The inspired partial pressure of oxygen (O2) is decreased as barometric pressure (PB) falls, leading to hypobaric hypoxia. In altitude acclimatized individuals or high-land natives, decreasing lactate accumulation in response to exercise has been reported (Hochachka et al 2002), suggesting metabolic shifts may occur with chronic compared to acute exposure (the lactate paradox). This is alongside alterations to the mitochondrial network, with exposure to ≥42 days being associated with decreasing mitochondrial density in skeletal muscle (Horscroft and Murray 2014). Further investigation into the effects of chronic hypobaric hypoxia is warranted
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