Exogenous Glucose Oxidation During Endurance Exercise in Hypoxia

Abstract

The exercise under hypoxic condition augmented carbohydrate (CHO) metabolism during exercise (Sumi et al. 2018). However, detailed CHO oxidation pattern during exercise under hypoxic condition remain unclear. PURPOSE: The purpose of the present study was to evaluate the effect of endurance exercise under moderate hypoxic condition at the same energy expenditure or exercise intensity on exogenous glucose oxidation. METHODS: Nine active healthy males completed three trials on different days, consisting of 30-min running at each exercise intensity of the following: 1) 65% of normoxic VO2max under the normoxic condition (FiO2 = 20.9%; NOR), 2) 65% of hypoxic VO2max under the hypoxic condition (FiO2 = 14.5%; HYPOR), 3) 65% of normoxic VO2max under the hypoxic condition (FiO2 = 14.5%; HYPOA). Venous blood samples were collected before and after exercise. The subjects consumed 13C-labeled glucose immediately before exercise, and we collected expired gas during exercise to determine 13C-excretion (calculated by 13CO2/12CO2). RESULTS: Running velocity were significantly lower in the HYPOR (9.4 ± 0.3 km) than in the NOR (10.6 ± 0.3 km) and HYPOA (10.6 ± 0.3 km). Exercise-induced blood lactate elevation was significantly augmented in the HYPOA than in the NOR and HYPOR (P = 0.001). The HYPOA showed significantly higher CHO oxidation (evaluated by VO2 and VCO2) during exercise compared with other two trials (P = 0.01). In contrast, exogenous glucose oxidation (13C-excretion) during exercise was significantly lower in the HYPOA than in the NOR (P = 0.01). CONCLUSIONS: Endurance exercise under moderate hypoxic conditions promoted whole body CHO metabolism during exercise. However, exogenous glucose oxidation during exercise was attenuated compared with the same exercise under normoxic condition.