Faculty of Health and Sports Sciences, Doshisha University, Tatara, Kyotanabe, Kyoto, Japan.
Faculty of Environmental and Symbiotic Sciences, Prefectural University of Kumamoto, Higashiku, Kumamoto, Japan.
PLoS One. 2018 Jul 25;13(7):e0200186. doi: 10.1371/journal.pone.0200186. eCollection 2018.
We investigated the effects of moderate hypoxia (FiO2 = 15%) on different kinetics between pulmonary ventilation ([Formula: see text]) and heart rate (HR) during treadmill walking. Breath-by-breath [Formula: see text], oxygen uptake ([Formula: see text]), carbon dioxide output ([Formula: see text]), and HR were measured in 13 healthy young adults. The treadmill speed was sinusoidally changed from 3 to 6 km·h-1 with four oscillation periods of 1, 2, 5, and 10 min. The amplitude (Amp), phase shift (PS) and mean values of these kinetics were obtained by harmonic analysis. The mean values of all of these responses during walking at a sinusoidally changing speed became greater under hypoxia compared to normoxia (FiO2 = 21%), indicating that moderate hypoxia could achieve an increased energy expenditure (increased [Formula: see text] and [Formula: see text]) and hyperventilation. The Amp values of the [Formula: see text], [Formula: see text], and [Formula: see text] kinetics were not significantly different between normoxia and hypoxia at most periods, although a significantly smaller Amp of the HR was observed at faster oscillation periods (1 or 2 min).The PS of the HR was significantly greater under hypoxia than normoxia at the 2, 5, and 10 min periods, whereas the PS of the [Formula: see text], [Formula: see text], and [Formula: see text] responses was not significantly different between normoxia and hypoxia at any period. These findings suggest that the lesser changes in Amp and PS in ventilatory and gas exchange kinetics during walking at a sinusoidally changing speed were remarkably different from a deceleration in HR kinetics under moderate hypoxia.
我们研究了在平板跑步机行走过程中，中度低氧（FiO2=15%）对肺通气（[Formula: see text]）和心率（HR）之间不同动力学的影响。13 名健康的年轻成年人进行了逐口气的[Formula: see text]、摄氧量（[Formula: see text]）、二氧化碳输出（[Formula: see text]）和 HR 测量。跑步机速度呈正弦波变化，从 3 公里/小时到 6 公里/小时，有四个 1、2、5 和 10 分钟的振荡周期。通过谐波分析获得这些动力学的幅度（Amp）、相位偏移（PS）和平均值。与常氧（FiO2=21%）相比，在正弦波变化速度下行走时，这些反应的平均值在低氧条件下均增大，表明中度低氧可实现能量消耗的增加（增加[Formula: see text]和[Formula: see text]）和过度通气。在大多数周期中，常氧和低氧条件下，[Formula: see text]、[Formula: see text]和[Formula: see text]动力学的 Amp 值没有显著差异，尽管在较快的振荡周期（1 或 2 分钟）观察到 HR 的 Amp 值显著较小。在 2、5 和 10 分钟周期中，HR 的 PS 在低氧条件下显著大于常氧条件，而在任何周期中，[Formula: see text]、[Formula: see text]和[Formula: see text]反应的 PS 没有显著差异。这些发现表明，在正弦波变化速度下行走时，通气和气体交换动力学中 Amp 和 PS 的变化较小，与中度低氧下 HR 动力学的减速明显不同。
