Maximal exercise at extreme altitudes on Mount Everest

West, John B.; Boyer, S. J.; Graber, David J.; Hackett, Peter H.; Maret, K. H.; Milledge, J. S.; Peters, Richard M.; Pizzo, C. J.; Samaja, Michele; Sarnquist, Frank H.

doi:10.1152/jappl.1983.55.3.688

Cited by 178 publications

(121 citation statements)

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“…By the end of aerobic dives, the arterial oxygen partial pressure (PaO∑) in Weddell seals is as low as 3.2×10 2 ·Pa (Qvist et al, 1986;Davis and Kanatous, 1999), which is equivalent to the degree of hypoxia experienced by human climbers on the top of Mt Everest (approximately 8850·m). At this altitude, the maximum oxygen consumption of climbers is reduced to 25% of that at sea level (West et al, 1983). Nevertheless, pinnipeds maintain aerobic metabolism during most free-ranging dives Davis et al, 1991;Hochachka, 1992;Butler and Jones, 1997).…”

mentioning

confidence: 93%

Adaptations to diving hypoxia in the heart, kidneys and splanchnic organs of harbor seals (Phoca vitulina)

Fuson

Cowan

Kanatous

et al. 2003

Journal of Experimental Biology

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Based on forced submergence studies conducted from the 1940s to the early 1970s, it was believed that marine mammals relied primarily on anaerobic metabolism during diving (Elsner and Gooden, 1983;Butler and Jones, 1997). After a forced submergence, there was a net accumulation of lactic acid in the plasma, indicating that anaerobic glycolysis had provided ATP as the organs and tissues became hypoxic. Therefore, it was assumed that marine mammals might have enhanced enzyme activities for anaerobic glycolysis. However, showed that, on average, marine mammals do not posses significantly elevated anaerobic enzyme activities when compared with terrestrial mammals. These results were difficult to reconcile with the apparent reliance of marine mammals on anaerobic metabolism during forced submergence. In the early 1980s, Kooyman et al. (1981) established the concept of the aerobic dive limit (ADL) by measuring the post-dive blood lactate concentration in Weddell seals (Leptonycotes weddellii) following voluntary dives from an isolated ice hole in Antarctica. The ADL is defined as the longest dive that a marine mammal can make while relying principally on oxygen stored in the lungs, blood and muscles to maintain aerobic metabolism. They found that dives shorter in duration than the ADL showed no post-dive increase in blood lactic acid, indicating that metabolism had remained aerobic. By attaching time-depth recorders to free-ranging Weddell seals, they showed that most voluntary dives were within the ADL. Similar results have been dehydrogenase (HOAD) activities in their swimming muscles to maintain an aerobic, fat-based metabolism during diving. The goal of this study was to determine whether the heart, kidneys and splanchnic organs have an elevated VV(mt) and CS and HOAD activities as parallel adaptations for sustaining aerobic metabolism and normal function during hypoxia in harbor seals (Phoca vitulina).Samples of heart, liver, kidney, stomach and small intestine were taken from 10 freshly killed harbor seals and fixed in glutaraldehyde for transmission electron microscopy or frozen in liquid nitrogen for enzymatic analysis. Samples from dogs and rats were used for comparison. Within the harbor seal, the liver and stomach had the highest VV(mt). The liver also had the highest CS activity. The kidneys and heart had the highest HOAD activities, and the liver and heart had the highest lactate dehydrogenase (LDH) activities. Mitochondrial volume densities scaled to tissue-specific resting metabolic rate [VV(mt)/RMR] in the heart, liver, kidneys, stomach and small intestine of harbor seals were elevated (range 1.2-6.6×) when compared with those in the dog and/or rat. In addition, HOAD activity scaled to tissue-specific RMR in the heart and liver of harbor seals was elevated compared with that in the dog and rat (3.2× and 6.2× in the heart and 8.5× and 5.5× in the liver, respectively). These data suggest that organs such as the liver, kidneys and stomach possess a heightened ability for aerobic, fatbased metabolism dur...

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mentioning

confidence: 93%

Adaptations to diving hypoxia in the heart, kidneys and splanchnic organs of harbor seals (Phoca vitulina)

Fuson

Cowan

Kanatous

et al. 2003

Journal of Experimental Biology

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“…Under exercise, these adaptive mechanisms are additionally stressed, and performance is, therefore, limited in the hypoxic environment at altitude. Several studies have described a decreased maximal workload (W max ) and V O 2 associated with decreasing barometric pressure and alveolar partial pressure of oxygen (PA O 2 ) (79,81). Thus exercise at altitude is associated with a sustainably elevated respiratory rate and consecutively increased minute ventilation (V E), even more upon acclimatization, which improves the arterial O 2 saturation from pulse oximetry (Sp O 2 ), but is associated with a lower arterial PCO 2 and higher ventilatory equivalents for V O 2 and CO 2 output (V CO 2 ) (V E/V O 2 and V E/V CO 2 , respectively), indicating ventilatory inefficiency (Figs.…”

Section: Introductionmentioning

confidence: 99%

Effect of hypoxia and hyperoxia on exercise performance in healthy individuals and in patients with pulmonary hypertension: a systematic review

Ulrich

Schneider

Bloch

2017

Journal of Applied Physiology

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Exercise performance is determined by oxygen supply to working muscles and vital organs. In healthy individuals, exercise performance is limited in the hypoxic environment at altitude, when oxygen delivery is diminished due to the reduced alveolar and arterial oxygen partial pressures. In patients with pulmonary hypertension, exercise performance is already reduced near sea level due to impairments of the pulmonary circulation and gas exchange and, presumably, these limitations are more pronounced at altitude. In studies performed near sea level in healthy subjects as well as in patients with pulmonary hypertension (PH) maximal performance during progressive ramp exercise and endurance of submaximal constant load exercise were substantially enhanced by breathing oxygen-enriched air. Both in healthy individuals and in PH-patients these improvements were mediated by a better arterial, muscular and cerebral oxygenation along with a reduced sympathetic excitation, as suggested by the reduced heart rate and alveolar ventilation at submaximal isoloads, and an improved pulmonary gas exchange efficiency, especially in patients with PH. In summary, in healthy individuals and in patients with pulmonary hypertension, alterations in the inspiratory PO2 by exposure to hypobaric hypoxia or normobaric hyperoxia reduce or enhance exercise performance, respectively, by modifying oxygen delivery to the muscles and the brain, by effects on cardiovascular and respiratory control and by alterations in pulmonary gas exchange. The understanding of these physiologic mechanisms helps counselling individuals planning altitude or air travel and prescribing oxygen therapy to patients with pulmonary hypertension. is determined by oxygen supply to working muscles and vital organs. In healthy individuals, exercise performance is limited in the hypoxic environment at altitude, when oxygen delivery is diminished due to the reduced alveolar and arterial oxygen partial pressures. In patients with pulmonary hypertension (PH), exercise performance is already reduced near sea level due to impairments of the pulmonary circulation and gas exchange, and, presumably, these limitations are more pronounced at altitude. In studies performed near sea level in healthy subjects, as well as in patients with PH, maximal performance during progressive ramp exercise and endurance of submaximal constant-load exercise were substantially enhanced by breathing oxygen-enriched air. Both in healthy individuals and in PH patients, these improvements were mediated by a better arterial, muscular, and cerebral oxygenation, along with a reduced sympathetic excitation, as suggested by the reduced heart rate and alveolar ventilation at submaximal isoloads, and an improved pulmonary gas exchange efficiency, especially in patients with PH. In summary, in healthy individuals and in patients with PH, alterations in the inspiratory PO 2 by exposure to hypobaric hypoxia or normobaric hyperoxia reduce or enhance exercise performance, respectively, by modifying oxygen deliv...

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“…Extreme altitude climbing has been traditionally studied by scientists and physicians in expeditions [43][44][45][46][47]. The rise in RHR and during exercise starts even at moderate altitudes [48] and returns to sea level values hours after descent.…”

Section: Discussionmentioning

confidence: 99%

Physiological and Kinanthropometrical Parameters of an Elite Climber. Single case study.

et al. 2012

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Maximal exercise at extreme altitudes on Mount Everest

Cited by 178 publications

References 20 publications

Adaptations to diving hypoxia in the heart, kidneys and splanchnic organs of harbor seals (Phoca vitulina)

Adaptations to diving hypoxia in the heart, kidneys and splanchnic organs of harbor seals (Phoca vitulina)

Effect of hypoxia and hyperoxia on exercise performance in healthy individuals and in patients with pulmonary hypertension: a systematic review

Physiological and Kinanthropometrical Parameters of an Elite Climber. Single case study.

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