著者

柳田 亮 小川 洋二郎 水落 文夫 鈴木 典 高橋 正則 岩崎 賢一

出版者

一般社団法人日本衛生学会

雑誌

日本衛生学雑誌 (ISSN:00215082)

巻号頁・発行日

vol.67, no.3, pp.417-422, 2012 (Released:2012-06-26)

参考文献数

17

被引用文献数

1

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Objective: Altitude training is frequently used for athletes requiring competitive endurance in an attempt to improve their sea-level performance. However, there has been no study in which the mechanisms by which spontaneous arterial-cardiac baroreflex function changes was examined in responders or nonresponders of altitude training. The purpose of this study was to clarify the different effects of altitude training on baroreflex function between responders and nonresponders. Methods: Twelve university student cross-country skiers (6 men, 6 women; age, 19±1 years) participated in the altitude training in a camp for 3 weeks, which was carried out in accordance with the method of Living High-Training Low. Baroreflex function was estimated by transfer function analysis before and after the training. Results: The responders of the training were 3 men and 2 women, and the nonresponders were 3 men and 4 women. In the responders, the transfer function gain in the high-frequency range significantly increased after the training (28.9→46.5 ms/mmHg p=0.021). On the other hand, no significant change in this index was observed in the nonresponders (25.9→21.2 ms/mmHg p=0.405). Conclusion: As indicated by the results of transfer function gain in the high-frequency range, the baroreflex function in the responders increased significantly after the altitude training, whereas no significant change was observed in the nonresponders.

著者

曷川 元 小川 洋二郎 青木 健 柳田 亮 岩崎 賢一

出版者

日本衛生学会

雑誌

日本衛生学雑誌 (ISSN:00215082)

巻号頁・発行日

vol.67, no.4, pp.508-513, 2012 (Released:2012-10-25)

参考文献数

24

被引用文献数

2

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Objectives: Acute hypoxia may impair dynamic cerebral autoregulation. However, previous studies have been controversial. The difference in methods of estimation of dynamic cerebral autoregulation is reported to be responsible for conflicting reports. We, therefore, conducted this study using two representative methods of estimation of dynamic cerebral autoregulation to test our hypothesis that dynamic cerebral autoregulation is impaired during acute exposure to mild hypoxia. Methods: Eleven healthy men were exposed to 15% oxygen concentration for two hours. They were examined under normoxia (21% O2) and hypoxia (15% O2). The mean arterial pressure (MAP) in the radial artery was measured by tonometry, and cerebral blood flow velocity (CBFv) in the middle cerebral artery was measured by transcranial Doppler ultrasonography. Dynamic cerebral autoregulation was assessed by spectral and transfer function analyses of beat-by-beat changes in MAP and CBFv. Moreover, the dynamic rate of regulation and percentage restoration of CBFv were estimated when a temporal decrease in arterial pressure was induced by thigh-cuff deflation. Results: Arterial oxygen saturation decreased significantly during hypoxia (97±0% to 88±1%), whereas respiratory rate was unchanged, as was steady-state CBFv. With 15% O2, the very-low-frequency power of CBFv variability increased significantly. Transfer function coherence (0.40±0.02 to 0.53±0.05) and gain (0.51±0.07 cm/s/mmHg to 0.79±0.11 cm/s/mmHg) in the very-low-frequency range increased significantly. Moreover, the percentage restoration of CBF velocity determined by thigh-cuff deflation decreased significantly during hypoxia (125±25% to 65±8%). Conclusions: Taken together, these results obtained using two representative methods consistently indicate that mild hypoxia impairs dynamic cerebral autoregulation.