LunHab: Interactive effects of a 10-day sustained exposure to hypoxia and bedrest on aerobic exercise capacity in male lowlanders

Abstract

The study examined the interactive effects of a 10-day exposure to hypoxia and bedrest on the whole body peak oxygen uptake () during maximal exercise, and on skeletal-muscle and cerebral oxygenation during submaximal exercise. Nine males underwent three 10-day confinements, in a Latin-square order: (i) a normoxic bedrest [NBR; partial pressure of inspired O₂ (P_IO₂) = 134.2 ± 0.7 mmHg], (ii) a hypoxic bedrest (HBR; P_IO₂ = 102.9 ± 0.1 mmHg at day 1, 91.5 ± 1.2 mmHg at days 3–10), and (iii) a hypoxic ambulation (HAMB; P_IO₂ as in HBR). Before, one (R + 1) and three (R+3) days after each confinement, subjects performed exhaustive, incremental-load and moderate-intensity constant-load (CLTs) cycle-ergometry trials, while breathing either room air, or a hypoxic gas mixture. During the CLTs, changes in the regional oxygenation of the cerebral frontal cortex, and the vastus lateralis and intercostal muscles were monitored with near-infrared spectroscopy. At R+1, the confinement-related impairment in was greater after HBR than after NBR or HAMB, regardless of whether the trial was performed in room-air or hypoxia (HBR: −16.2%, NBR: −8.3%, HAMB: −4.1%; P = 0.001). During the CLTs, bedrest aggravated the exercise-induced reduction in locomotor- and respiratory-muscle oxygenation (P ≤ 0.05); an effect that was less after HBR than after NBR (P ≤ 0.05). The hypoxia exercise-induced cerebral vasodilatatory response was blunted by HBR, likely due to the marked hyperventilation-dependent hypocapnea, attendant to the sustained hypoxic stimulus. Hence, short-term exposure to hypoxia potentiates the reduction in , but it mitigates the impairment in skeletal-muscle oxidative capacity induced by bedrest.

This article is protected by copyright. All rights reserved

from #MedicinebyAlexandrosSfakianakis via xlomafota13 on Inoreader http://ift.tt/2ogDPc6
via IFTTT