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LunHab: interactive effects of a 10 day sustained exposure to hypoxia and bedrest on aerobic exercise capacity in male lowlanders
Author(s) -
Keramidas Michail E.,
Mekjavic Igor B.,
Eiken Ola
Publication year - 2017
Publication title -
experimental physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.925
H-Index - 101
eISSN - 1469-445X
pISSN - 0958-0670
DOI - 10.1113/ep086167
Subject(s) - hypoxia (environmental) , oxygenation , skeletal muscle , vastus lateralis muscle , aerobic exercise , medicine , chemistry , oxygen , organic chemistry
New FindingsWhat is the central question of this study? What are the distinct and interactive effects of a 10 day exposure to hypoxia and horizontal bedrest on the whole‐body peak oxygen uptake and on the regional cerebral and skeletal muscle tissue oxygenation during upright cycle ergometry in male lowlanders?What is the main finding and its importance? A 10 day sustained exposure to hypoxia aggravates the bedrest‐induced reduction in peak oxygen uptake during dynamic exercise engaging large muscle groups, but mitigates the skeletal muscle oxidative capacity impairment elicited by bedrest.The study examined the interactive effects of a 10 day exposure to hypoxia and bedrest on the whole‐body peak oxygen uptake ( V ̇O 2 peak) 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, as follows: (i) a normoxic bedrest [NBR; partial pressure of inspired O 2 ( P I , O 2) = 134.2 ± 0.7 mmHg]; (ii) a hypoxic bedrest (HBR; P I , O 2 = 102.9 ± 0.1 mmHg at day 1, 91.5 ± 1.2 mmHg at days 3–10); and (iii) a hypoxic ambulation (HAMB; P I , O 2as in HBR). Before, 1 (R+1) and 3 days (R+3) 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 inV ̇O 2 peakwas 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 hypoxic exercise‐induced cerebral vasodilatory response was blunted by HBR, probably because of the marked hyperventilation‐dependent hypocapnia, attendant to the sustained hypoxic stimulus. Hence, short‐term exposure to hypoxia potentiates the reduction inV ̇O 2 peak, but it mitigates the impairment in skeletal muscle oxidative capacity induced by bedrest.