Effects of Various Hypoxia vs Normoxia on Metabolic and Skeletal Muscle Oxygenation Function during Graded Exercise in Healthy Males

Abstract

Purpose The purpose of this study was to investigate the effect of various hypoxia vs. normoxia on metabolic and skeletal muscle oxygenation function during grated exercise and exercise performance. Methods Eleven healthy male participants (21.5 ± 2.3 years) performed graded exercise test (GXT) using cycle ergometer at sea‐level (760 mmHg) and under various hypobaric hypoxia (1,500 m simulated altitude; 634 mmHg, 3,000 m simulated altitude; 528 mmHg and 4,500 m simulated altitude; 433 mmHg) in a random order. GXT starts at 300 kg·m·min−1 (50 watts) and increases by 150 kg·m·min−1 (25 watts) every 2 minutes until exhaustion. The pedal frequency was set at 60 rpm. Metabolic parameters (peripheral capillary oxygen saturation; SPO2, heart rate; HR, minute ventilation; VE, oxygen consumption; VO2, carbon dioxide excretion; VCO2, respiratory exchange ratio; RER, oxygen pulse, and blood lactate) and skeletal muscle oxygen profiles (oxygenated hemoglobin and myoglobin; OxyHb, deoxygenated hemoglobin and myoglobin; DeoxyHb, and tissue oxygen saturation; StO2) were measured every 1 minute during the GXT, and it also evaluated at exercise load of 50, 75, 100, 125, and 150 watts on ergometers under various hypoxia vs. normoxia. Exercise performance was evaluated by maximal oxygen consumption, peak power, and exercise time obtained through GXT. Results In metabolic parameters, HR, VE, VCO2, RER, and blood lactate showed a significant increase in hypoxia compared with normoxia. Also, the increase was more pronounced as the hypoxia became more severe. However, SPO2, VO2, and O2pulse presented a significant decrease in hypoxia compared with normoxia. Also, the decrease was more pronounced as the hypoxia became more severe. In skeletal muscle oxygen profiles, OxyHb showed a significant decrease in 3,000 m and 4,500 m simulated altitude compared with normoxia. In exercise performance, VO2max and peak power were significantly decreased in 3,000 m and 4,500 m simulated altitude compared with normoxia, and exercise time decreased significantly with increasing simulated altitude. Conclusion These showed a decrease in exercise performance due to a decrease in metabolic parameters and skeletal muscle oxygenation in hypoxia vs. normoxia, and more pronounced as the hypoxia became more severe. Support or Funding Information