Impact of exercise and moderate hypoxia on glycemic regulation and substrate oxidation pattern.

We examined metabolic and endocrine responses during rest and exercise in moderate hypoxia over a 7.5 h time courses during daytime.Eight 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.The 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).Three 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

Physical characteristics and fitness.

<p>mean ± SE.</p><p>Physical characteristics and fitness.</p

Time-course changes and area under the curve of blood glucose (A) and serum insulin (B) concentrations over 7.5 h.

<p>Each period of exercise is indicated by the shaded boxes. The arrow indicates the time of meal consumption. c; <i>P</i><0.05, NOR-Rest vs. NOR-Ex. d; <i>P</i><0.05, HYP-Rest vs. HYP-Ex.</p

Time-course changes of SpO₂ (A) and HR (B) over 7.5 h.

<p>Each period of exercise is indicated by the shaded boxes. The arrow indicates the time of meal consumption. a; <i>P</i><0.05, NOR-Rest vs. HYP-Rest. b; <i>P</i><0.05, NOR-Ex vs. HYP-Ex. c; <i>P</i><0.05, NOR-Rest vs. NOR-Ex. d; <i>P</i><0.05, HYP-Rest vs. HYP-Ex.</p

Time-course changes of FFA (A), glycerol (B) and lactate (C) concentrations over 7.5 h.

<p>Each period of exercise is indicated by the shaded boxes. The arrow indicates the time of meal consumption. c; <i>P</i><0.05, NOR-Rest vs. NOR-Ex. d; <i>P</i><0.05, HYP-Rest vs. HYP-Ex.</p