Cerebral hemodynamics and oxygenation during whole-body exercise for five days at high altitude.

What is the central question of this study? Impairment and subsequent improvement in cerebral oxygenation during acute and prolonged exposure to high altitude affects exercise performance. However, this study innovates by investigating the effect of acute and prolonged high-altitude exposure on cerebral hemodynamics during a submaximal endurance exercise performed at the same relative intensity. What is the main finding and its importance? Despite exercising at the same relative intensity at sea level and high altitude, participants showed a sustained impairment in cerebral oxygenation after prolonged exposure to high altitude, which may contribute to the absence of improvement in exercise tolerance.
Deterioration and subsequent improvement in cerebral oxygenation during acute and prolonged hypoxic exposure may affect whole-body exercise performance at high altitude. This study investigated the effect of hypoxic exposure on cerebral hemodynamics at different cortical locations during exercise at the same relative intensity following one (D1) and five days (D5) at 4,350 m. Eleven male subjects performed a submaximal cycling exercise (6 min at 35% + 6 min at 55% + time-to-exhaustion at 75% of peak workrate achieved in the same condition, i.e. normoxia or hypoxia) at sea level (SL), D1 and D5. Transcranial Doppler and near-infrared spectroscopy assessed middle cerebral artery velocity (MCAv) and prefrontal and motor cortex oxygenation, respectively. Despite using the same relative intensity, exercise duration was reduced at D1 (22.7 ± 5.1 min) compared to SL (32.2 ± 9.0 min; p < 0.001) with no improvement at D5 (20.9 ± 6.3 min; p > 0.05). MCAv during exercise was elevated at D1 (+18.2%) and D5 (+15.0%) compared to SL (p < 0.001). However, prefrontal and motor cortex oxygenation were reduced at D1 and D5 compared to SL (p < 0.001). This pattern was of similar magnitude between cortical locations while total hemoglobin concentration increased to a larger extent in the prefrontal vs. motor cortex at exhaustion at D1 and D5. In contrast to our primary hypothesis, prefrontal and motor cortex oxygenation and exercise performance did not improve over 5 days at 4,350 m. Sustained impairment in cerebral oxygenation may contribute to the absence of improvement in exercise performance after partial acclimatization to high altitude. This article is protected by copyright. All rights reserved.

This article is protected by copyright. All rights reserved.