Author(s): TAKEHIRA, N., ATSUSHI, S., JULIEN, M.M., Institution: KYUSHU SANGYO UNIVERSITY, Country: JAPAN, Abstract-ID: 1506

INTRODUCTION:
Astronauts undergo physical adaptation training in a hyperbaric oxygen (HBO) or underwater environment. HBO has been reported to be effective in treating decompression sickness and improving athletic performance by increasing the partial pressure of oxygen in the body, blood volume, and dissolved oxygen levels. In addition, eicosapentaenoic acid (EPA) has been shown to reduce muscle inflammation after exercise and improve vascular endothelial function. However, most previous studies on EPA intake and vascular endothelial function have targeted subjects with specific diseases, and there are only a limited number of studies on healthy young adults. The aim of this study was to clarify the effects of physical exercise and EPA intake in a HBO environment on blood components and vascular endothelial function.
METHODS:
This study was a randomised crossover trial. The subjects (n=16) were divided into two groups (HBO group: n=8, C group: n=8), and during the first, middle and final stages of the experiment, they underwent medical examinations including blood sampling, and had their morphology, body composition and vascular endothelial function measured. The HBO environment was 1.41±0.008 ATA, 21.7±0.7℃, 73.5±4.6%, and the normal environment was 1.00±0.998 ATA, 22.1±1.1℃, and 70.5±6.5%. Exercise was performed twice a week for 8 weeks, for 60 minutes each time, at 60-70% of VO₂peak. The number of revolutions of the bicycle ergometer was set at 50-60 rpm. After a 4-week washout period, each group continued the same exercise in the other environment. EPA was taken as a supplement at a dose of approximately 2 g/day for 8 weeks. Repeated measures two-way analysis of variance was used for statistical analysis, and the significance level was set at less than 5%. This study was conducted with the approval of the Kyushu Sangyo University Ethics Review Committee (2023-0006) and was supported by a Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (23K01975).
RESULTS:
There was an interaction between the environment (HBO vs. C environment) and time (before and after the experiment) for red blood cell count, haematocrit value, HDL cholesterol value, and BFA, an interaction between environment (HBO vs. C) and time (before and after the experiment) was observed (red blood cell count: F=7.16, p=0.012, η²=0.19, haematocrit: F=6.12, p=0.019, η²=0.17, HDL cholesterol: F=5.35, p=0.028 , η²=0.15, BFA: F=7.16, p=0.012, η²=0.19). However, there were no significant changes in red blood cell count, hematocrit, or HDL cholesterol levels in the HBO environment (p>0.05), and Brachial Flow Acceleration increased slightly in the normal environment, but not significantly (p>0.05).
CONCLUSION:
Physical exercise and EPA intake in an HBO environment may improve blood flow and reduce blood viscosity, but there is a suggestion that in the long term they may cause a decrease in oxygen transport capacity and an increased risk of anaemia.