Interstitial Glucose Concentration & Sleep Quality During Night After Endurance Exercise In Hypoxia

Exercise under hypoxic condition has been previously shown to cause health benefits in various type of populations (Montero & Lundby, 2016; Mai et al., 2022). Endurance exercise in hypoxia promotes sympathetic nerve activity, but the change in metabolic regulations (e.g., glucose regulations, sympathetic nerve activity) during night following the exercise in hypoxia remain unclear. PURPOSE: To clarify the impacts of endurance exercise in hypoxia on nocturnal interstitial glucose concentration (IGC), sympathetic nerve activity and sleep quality. METHODS: Seven young people (6 men and 1 woman, 21 ± 1.0 years) were recruited for the study. All of them carried out three trials on different days: (1) pedaling exercise in normoxia (FiO2: 20.9%; NOR), (2) pedaling exercise in hypoxia (FiO2: 14.5%; HYP), and (3) rest in normoxia (REST). Each trial was separated at least one week, with randomized orders. The exercise consisted of 60 min of pedaling exercise at 50 % of maximal oxygen uptake (70 rpm), and it was started at 15:00 PM. During exercise, heart rate (HR), arterial oxygen saturation (SpO2), and rating of perceived exertion (RPE), and IGC were determined. In REST trial, the subjects rested for 60 min. Also, IGC and heart rate variability (HRV), and sleep quality (evaluated by actigraph) were continuously monitored during night (0:00 AM-8:00 AM). RESULTS: During exercise, HR showed significantly higher value in HYP and NOR than in REST (p < 0.001). In addition, SpO2 was significantly lower in HYP (85.4 ± 0.8%) than in NOR (97.0 ± 0.3%) and REST (97.1 ± 0.3%, p < 0.001). The average of IGC during exercise was significantly lower in NOR than REST (p < 0.05). During sleep (0:00 AM-8:00 AM), NOR showed lower IGC compared with REST (p < 0.05), but no significant difference was found between NOR and HYP. HRV (HF, LF/HF) and sleep quality (sleep latency, sleep efficacy, wake time after sleep onset, and total sleep time) during night did not differ significantly among three trials (p > 0.05). CONCLUSION: These findings suggest that endurance exercise in hypoxia does not interfere nocturnal changes in IGC, HRV and sleep quality compared with the same exercise in normoxia.