Effects of hyperbaric oxygen preconditioning on human energy metabolism when exposed to simulated 4 000 m acute hypoxia

Objective To investigate the effects of hyperbaric oxygen preconditioning (HBOP) on human energy metabolism and antioxidant under acute hypoxia exposure, so as to provide new measures for the improvement of physical performance in those with acute hypoxia. Methods Eight healthy subjects had respectively 3-day, 5-day and 7-day HBOP, then, they underwent acute exposure to a simulated high altitude of 4 000 m. Exercise load experiments were conducted both before and after HBOP. Levels of glucose (Glu), blood lactate (BLA), lactate dehydrogenase (LDH) and superoxide dismutase(SOD)were detected both before and after physical exercises. Results Following HBOP, no significant changes could be noticed in Glu level in the subjects, who underwent simulated 4 000 m physical exercise and its level remained relatively high during exposure(P>0.05). During exposure to hypoxia at an altitude of 4 000 m, BLA level both at rest and under physical exercise[(3.3±0.8)、(6.7±2.0) mmol/L] elevated signficantly, as compared with that at the sea level[(2.4±0.7)mmol/L], and statistical differences could be noted, when comparisons were made between them(P<0.05 or P<0.01). Following 7-day HBOP, the BLA levels after physical load [(4.5±1.3)mmol/L] were significantly decreased, as compared with those detected at 4 000 m, and at the same time, LDH activity was obviously elevated, with statistical significance(P<0.05). As compared with that of the control value at 4 000 m[(6.7±2.0)mmol/L], LDH levels after 3-day and 7-day HBOP were increased to some extent, which were equivalent to the control value at the sea level. After HBOP, GSH levels both at rest and under physical exercise were almost the same as that of the sea level, without statistical signficance(P<0.05). And no statistical significace could be seen in the changes of nergy metabolism, when comparisons were made between them (P<0.05). Conclusions Before acute hypoxia exposure, 3-day HBOP would enable the human body under physical load to maintain Glu at a relatively high level, increase LDH activity and help to decrease BLA level signfificantly, and at the same time, help to maintain the level of antioxidant at the sea level. For this reason, HBOP seemed to have positive effects on anti-oxidation, anti-fatigue and enhancement of physical performance under acute hypoxia. Key words: Hyperbaric oxygen preconditioning; Acute hypoxia exposure; Physical load; Energy metabolism; Antioxidant