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PlanHab: Hypoxia exaggerates the bedrest-induced reduction in peak oxygen uptake during upright cycle-ergometry
KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
KTH, School of Technology and Health (STH), Basic Science and Biomedicine, Environmental Physiology.
2016 (English)In: American Journal of Physiology. Heart and Circulatory Physiology, ISSN 0363-6135, E-ISSN 1522-1539Article in journal (Refereed) Published
Abstract [en]

The study examined the effects of hypoxia and horizontal bedrest, separately and in combination, on peak oxygen uptake (VO2peak) during upright cycle-ergometry. Ten male lowlanders underwent three 21-day confinement periods, in a counterbalanced order: i) normoxic bedrest (NBR; PIO2 = 133.1 ± 0.3 mmHg), ii) hypoxic bedrest (HBR; PIO2 = 90.0 ± 0.4 mmHg), and iii) hypoxic ambulation (HAMB; PIO2 = 90.0 ± 0.4 mmHg). Before and after each confinement, subjects performed two incremental-load trials to exhaustion, while inspiring either room-air (AIR), or a hypoxic gas (HYPO; PIO2 = 90.0 ± 0.4 mmHg). Changes in regional oxygenation of the vastus lateralis muscle and the frontal cerebral cortex were monitored with near-infrared spectroscopy. Cardiac output (CO) was recorded using a bioimpedance method. The AIR VO2peak was decreased by both HBR (~13.5%; p ≤ 0.001) and NBR (~8.6%; p ≤ 0.001), with greater drop after HBR (p = 0.01). The HYPO VO2peak was also reduced by HBR (-9.7%; p ≤ 0.001) and NBR (-6.1%; p ≤ 0.001). Peak CO was lower after both bedrest interventions, and especially after HBR (HBR: ~13%, NBR: ~7%; p ≤ 0.05). Exercise-induced alterations in muscle and cerebral oxygenation were blunted in a similar manner after both bedrest confinements. No changes were observed in HAMB. Hence, the bedrest-induced decrease in VO2peak was exaggerated by hypoxia, most likely due to a reduction in convective O2 transport, as indicated by the lower peak values of CO.

Place, publisher, year, edition, pages
American Physiological Society , 2016.
National Category
Physiology
Identifiers
URN: urn:nbn:se:kth:diva-189194DOI: 10.1152/ajpheart.00304.2016OAI: oai:DiVA.org:kth-189194DiVA: diva2:944071
Note

QC 20160713

Available from: 2016-06-28 Created: 2016-06-28 Last updated: 2016-07-13Bibliographically approved

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Keramidas, Michail E.Kölegård, RogerEiken, Ola
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