ABSTRACT
<p>We developed a periodic hypobaric hypoxic environment (PHHE) system. Characteristics of this system varied between decreased pressure at an altitude of 1,500 m for 180 seconds and increased pressure at an altitude of 0 m for 180 seconds. The present study aimed to determine the effects of PHHE on physiological responses during endurance exercise and recovery after exercise. This study included 12 healthy men, and they provided written informed consent. All subjects performed a cycling exercise for 30 minutes and recovered after exercise for 10 minutes. The exercise protocol was performed with 20% maximum oxygen uptake for 6 minutes (warm-up), 40 % for 18 minutes (main exercise), and 20 % for 6 minutes (cool down). We established two experimental conditions: exercise with the PHHE and the control (C). The C condition involved exercise using the PHHE at an altitude of 0 m, and the atmospheric pressure was not changed. In the PHHE condition, the atmospheric pressure was changed periodically from 967 to 817 hPa (the external pressure was 1,008 hPa). Subjects’ heart rate (HR), blood pressure (BP), arterial oxygen saturation (SpO<sub>2</sub>), rating of perceived exertion, and respiratory responses were measured in both conditions. The SpO<sub>2</sub>, HR and systolic BP during exercise were significantly lower in the PHHE condition than in the C condition. The HR post-exercise was significantly lower. After exercise, the ln HF, an index of cardiac parasympathetic nervous system modulation, was significantly higher. In conclusion, during endurance exercise, cardiocirculatory responses in the PHHE condition were decreased.</p>