We investigated the effects of hypoxia on neurophysiological parameters during rest and moderate intensity exercise to understand cerebral metabolism. 31 male (age= 31±13 yr, height= 177±5 cm, mass= 79±9 kg) and 4 female (age= 25±7 yr, height= 169±7 cm, mass= 60±5kg) participants were recruited. Near-infrared spectroscope (NIRS) was placed over the right prefrontal cortex to measure relative changes in oxy (HbO2), deoxy (HHb), total (tHb) and hemoglobin difference (HbDiff). Participants rested in a supine position for 30-minutes, followed by a 2-minute washout period before beginning a 10-second squat-stand (0.05 Hz) maneuver for 5 minutes. Thereafter participants repeated the supine and squat-stand protocol in a normobaric environmental chamber (14.8% oxygen; ~2750m). The difference from the last 5 minutes of supine rest was compared to the first 5 minutes in both conditions. The difference between the supine rest vs. squat-stand was compared in both conditions. NIRS standard deviation (SD) was compared during the 30-minutes of supine rest vs. the 5 minutes of squat-stand. A Wilcoxon signed-rank test was use to compare paired samples. Results showed a significant decrease in HbO2, tHb and HbDiff, a significant increase in HHb at the end of the supine rest in hypoxia vs. normoxia, and an increase in SD of all parameters in hypoxia. For squat-stand, there was a significant decrease in HbDiff and a significant increase in HHb in hypoxia, with a significant increase in SD of all parameters in hypoxia. These results suggest altered cerebral metabolism at altitudes about 2750m during rest and exercise.
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