| Purpose:VO2max will decline in acute hypoxia, domestic and foreign researches focused on the effect of the variations of the pulmonary ventilation, pulmonary gas exchange and the reducation of the SPO2 on VO2max, while the study about the influence of skeletal muscle metabolism on oxygen uptake was atively fewer. The purpose of this study was to observe the level of the decline in VO2peak of lowlanders in acute hypoxia, summarize the variations of glycometabolism related index; explore the relationship between the the decline in VC^peak and the variations of glycometabolism by combining the variation of the ratio of the supplement of glycolipid, lactate metabolism and the regulating hormones when exposure to different level of simulated acute hypoxia.Method:12 healthy men performed three incremental tests under normoxic condition and at a simulated altitude of 2500m and 4500m normobaric hypoxia condition in a random order, each separated by about 7 days. Subjects came into the test condtion without eating anyting within 12 hours, and took 2ml venous blood samples for the measurement of fasting INS and glucose; they came into the test condition after finishing eating 1h later. lOul capillary samples for the measurement of resting lactate were taken from fingertips, and 4ml venous blood samples were taken for the measurement of plasma CA and serum INS before exercise. We usd a supine position bicycle ergometer, and recorded all the data from gas metabolism 5min before exercise. Than recorded all the data from gas metabolism during the tests, and took capillary samples for the measurement of lactate during the last 15s of each exercise step.4ml venous blood samples were taken for the measurement of CA and INS after exercise, and capillary samples for the measurement of lactate were taken during recovery period. All the data which were gotten from the tests were disposed and analysed, and calculated the lactate threshold, the energy provided by carbohydrate, HOMA-IR, etc.Result:(1) The VO2peak in hypoxia was significantly lower than it in normoxic (p?0.01); while the time when arrived at VO2peak during exercise was significantly shorter than it in normoxic (p<0.01). (2) The rRER at 4500mwas higher than it in normoxic and at 2500m (p<0.05). (3) The total energy output before exercise in hypoxia was higher than it in normoxic (p<0.01, p<0.05); the energy provided by carbohydrate when arrived at VO2peak at 4500m was lower than at 2500m (p<0.05), as well as the total energy output (p<0.05). (4) The corresponding exercise load when arrived at lactate threshold in hypoxia was lower than it in normoxic (p<0.05, p<0.01); and the lactate clearance rate at 4500m was lower than it at 2500m (p<0.05). (5) The concentration of EPI and NE was significantly higher at 4500m than it in normoxic and at 2500m (p<0.01). (6) INS concentration was significantly lower at 4500m than in normoxic and at 2500m (p?0.01), while the HOMA-IS in hypoxia was significantly lower than it in normoxic (p<0.01).Conclusion:(1) VO2peak was significantly lower than the normoxic by 12% and 20% at 2500m and 4500m, respectively, the time when exercised to the exhaustion cut down. With the increasement of altitude, the variation of the decline in VO2peak and the shortening in exercise time would be liner across the range from normoxic to 4500m hypoxia. (2) When exposure to 4500m of acute hypoxia, the consumption of the substance of energy source increased at rest, while the oxidation of carbohydrate decreased during the incremental exercise so that it couldn't provide enough energy for exercise. At the same time, the lactate threshold decreased, the corresponding exercise load when arrived at lactate threshold decreased, and the lactate clearance rate decreased after exercise. And the concentration of CA increased while the concentration of INS and HOMA-IS decreased. (3) The increase of the consumption of carbohydrate and the lack of energy is one of the reason of the decline in VO2peak when exposure to 4500m of acute hypoxia. |
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