ISSUL institute of Sport Sciences, University of Lausanne, Lausanne, 1015, Switzerland,
Eur J Appl Physiol. 2014 May;114(5):1037-48. doi: 10.1007/s00421-014-2835-8. Epub 2014 Feb 9.
The Richalet hypoxia sensitivity test (RT), which quantifies the cardiorespiratory response to acute hypoxia during exercise at an intensity corresponding to a heart rate of ~130 bpm in normoxia, can predict susceptibility of altitude sickness. Its ability to predict exercise performance in hypoxia is unknown.
Investigate: (1) whether cerebral blood flow (CBF) and cerebral tissue oxygenation (O2Hb; oxygenated hemoglobin, HHb; deoxygenated hemoglobin) responses during RT predict time-trial cycling (TT) performance in severe hypoxia; (2) if subjects with blunted cardiorespiratory responses during RT show greater impairment of TT performance in severe hypoxia.
Thirteen men [27 ± 7 years (mean ± SD), Wmax: 385 ± 30 W] were evaluated with RT and the results related to two 15 km TT, in normoxia and severe hypoxia (FIO2 = 0.11).
During RT, mean middle cerebral artery blood velocity (MCAv: index of CBF) was unaltered with hypoxia at rest (p > 0.05), while it was increased during normoxic (+22 ± 12 %, p < 0.05) and hypoxic exercise (+33 ± 17 %, p < 0.05). Resting hypoxia lowered cerebral O2Hb by 2.2 ± 1.2 μmol (p < 0.05 vs. resting normoxia); hypoxic exercise further lowered it to -7.6 ± 3.1 μmol below baseline (p < 0.05). Cerebral HHb, increased by 3.5 ± 1.8 μmol in resting hypoxia (p < 0.05), and further to 8.5 ± 2.9 μmol in hypoxic exercise (p < 0.05). Changes in CBF and cerebral tissue oxygenation during RT did not correlate with TT performance loss (R = 0.4, p > 0.05 and R = 0.5, p > 0.05, respectively), while tissue oxygenation and SaO2 changes during TT did (R = -0.76, p < 0.05). Significant correlations were observed between SaO2, MCAv and HHb during RT (R = -0.77, -0.76 and 0.84 respectively, p < 0.05 in all cases).
CBF and cerebral tissue oxygenation changes during RT do not predict performance impairment in hypoxia. Since the changes in SaO2 and brain HHb during the TT correlated with performance impairment, the hypothesis that brain oxygenation plays a limiting role for global exercise in conditions of severe hypoxia remains to be tested further.
Richalet 缺氧敏感测试（RT）可量化运动时急性缺氧的心肺反应，运动强度对应于常氧下 130 次/分钟的心率，可预测高原病的易感性。但其预测缺氧运动表现的能力尚不清楚。
研究：（1）RT 期间脑血流（CBF）和脑氧合（O2Hb；氧合血红蛋白，HHb；去氧血红蛋白）的变化是否可以预测严重缺氧时的计时赛（TT）表现；（2）如果 RT 期间心肺反应迟钝的受试者在严重缺氧时 TT 表现受损更大。
13 名男性[27 ± 7 岁（均值 ± 标准差），Wmax：385 ± 30 W]接受 RT 评估，并将结果与两次 15 公里 TT 在常氧和严重缺氧（FIO2 = 0.11）下进行比较。
在 RT 期间，休息时大脑中动脉平均血流速度（MCAv：CBF 指数）在缺氧时没有改变（p > 0.05），而在常氧运动时增加了（+22 ± 12%，p < 0.05）和缺氧运动时增加了（+33 ± 17%，p < 0.05）。休息时缺氧使脑 O2Hb 降低 2.2 ± 1.2 μmol（p < 0.05 与休息时常氧相比）；缺氧运动时进一步降低至基线以下-7.6 ± 3.1 μmol（p < 0.05）。休息时脑 HHb 增加 3.5 ± 1.8 μmol（p < 0.05），在缺氧运动时进一步增加到 8.5 ± 2.9 μmol（p < 0.05）。RT 期间 CBF 和脑氧合的变化与 TT 表现损失无关（R = 0.4，p > 0.05 和 R = 0.5，p > 0.05），而 TT 期间氧合和 SaO2 的变化则与 TT 表现损失有关（R = -0.76，p < 0.05）。在 RT 期间观察到 SaO2、MCAv 和 HHb 之间存在显著相关性（R = -0.77、-0.76 和 0.84，p < 0.05）。
RT 期间 CBF 和脑氧合的变化不能预测缺氧时的运动表现受损。由于 TT 期间 SaO2 和脑 HHb 的变化与运动表现受损相关，因此脑氧合在严重缺氧条件下对全身运动的限制作用仍有待进一步验证。
