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 (SpO₂), rating of perceived exertion, and respiratory responses were measured in both conditions. The SpO₂, 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.

The purpose of the present study was to indicate the relationship between health-related quality of life (HRQOL) measures, the daily rhythm of oral temperature (OT), and lifestyle. Five-hundred young men volunteered to participate in this study. Their OT, measured using a digital thermometer, was recorded every 2h from the time they woke up to the time they went to sleep for 1 week. The daily rhythm of OT was calculated as a quadratic function using the 1-week data. The HRQOL was measured using the Short-Form 36-Item Health Survey version 2 (SF-36v2). The participants were divided into 3 groups: a high-value group (HG) with ≥ 55 points of each summary score and each subscale score, a middle-value group (MG) with score > 45 and < 55 points, and a low-value group (LG) with score ≤ 45 points. Lifestyle was assessed in terms of eating habits, sleeping and exercise, and the presence of unidentified complaints. At the mental component summary, the OT at the time of waking up and the peak OT in the HG were significantly higher than those in the LG. At the physical and mental component summary, lifestyle in the HG was more favorable. These data suggest that the daily rhythms of OT may reflect the mental health status of an individual. The entraining factors in circadian variation might play a role in improving mental health and reducing unidentified complaints. In conclusion, there appears to be an association between mental health status, lifestyle, and daily rhythms of OT.

The purpose of this study was to determine the effects of supine floating on rectal temperature and cardiac autonomic nervous system activity after exercise. Seven healthy males volunteered for this study. Subjects performed supine position for 30 minutes in both control condition (C-condition) and water condition (W-condition) after exercise with a cycle ergometer for 15 minutes. Exercise intensity was high (80%VO₂max) and moderate (60%VO₂max). Water temperature was 30 degrees Celsius. Rectal temperature of post exercise showed no significant differences under the W-condition, as compared to the C-condition. Delta rectal temperature (point 0-0 was end of exercise) was significantly reduced (p<0.05) under the W-condition, as compared to the C-condition. Log HF was significantly increased (p<0.05) under the W-condition, as compared to the C-condition. These data suggested that supine floating after high and moderate intensity exercise could promote recovery of rectal temperature and increased in cardiac parasympathetic nervous system activity.