Abstract
ObjectiveWe examined metabolic and endocrine responses during rest and exercise in moderate hypoxia over a 7.5 h time courses during daytime.MethodsEight sedentary, overweight men (28.6±0.8 kg/m2) completed four experimental trials: a rest trial in normoxia (FiO2 = 20.9%, NOR-Rest), an exercise trial in normoxia (NOR-Ex), a rest trial in hypoxia (FiO2 = 15.0%, HYP-Rest), and an exercise trial in hypoxia (HYP-Ex). Experimental trials were performed from 8:00 to 15:30 in an environmental chamber. Blood and respiratory gas samples were collected over 7.5 h. In the exercise trials, subjects performed 30 min of pedaling exercise at 60% of VO2max at 8:00, 10:30, and 13:00, and rested during the remaining period in each environment. Standard meals were provided at 8:30, 11:00, and 13:30.ResultsThe areas under the curves for blood glucose and serum insulin concentrations over 7.5 h did not differ among the four trials. At baseline, %carbohydrate contribution was significantly higher in the hypoxic trials than in the normoxic trials (P<0.05). Although exercise promoted carbohydrate oxidation in the NOR-Ex and HYP-Ex trials, %carbohydrate contribution during each exercise and post-exercise period were significantly higher in the HYP-Ex trial than in the NOR-Ex trial (P<0.05).ConclusionThree sessions of 30 min exercise (60% of VO2max) in moderate hypoxia over 7.5 h did not attenuate postprandial glucose and insulin responses in young, overweight men. However, carbohydrate oxidation was significantly enhanced when the exercise was conducted in moderate hypoxia.
Highlights
Obesity leads to multiple metabolic disorders, including insulin resistance and postprandial hyperglycemia
We revealed that 4 weeks of endurance training under hypoxic conditions resulted in greater improvement of postprandial hyperglycemia than training under normoxic conditions [4]
Blood glucose concentrations were significantly lower after 60 min of rest or exercise under hypoxic condition compared with baseline values
Summary
Obesity leads to multiple metabolic disorders, including insulin resistance and postprandial hyperglycemia. Exercise is an important ‘therapy’ in the treatment of postprandial hyperglycemia because muscle contraction stimulates glucose uptake by skeletal muscle [1,2,3]. Blood glucose concentrations were significantly lower after 60 min of rest or exercise under hypoxic condition compared with baseline values. The mechanism of glucose lowering by hypoxic exposure is not fully understood, changes in substrate utilization patterns may be involved because acute exercise under hypoxic conditions increases carbohydrate oxidation [6,7,8]. Enhanced glucose uptake by skeletal muscle is thought to account for increased carbohydrate oxidation under hypoxic conditions. Several studies have demonstrated that severe hypoxia stimulates the translocation of glucose across the plasma membrane [9,10]
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