Faculty of Health and Life Sciences, Northumbria University, Newcastle, UK.
Acta Physiol (Oxf). 2014 Apr;210(4):875-88. doi: 10.1111/apha.12241.
We asked whether acclimatization to chronic hypoxia (CH) attenuates the level of supraspinal fatigue that is observed after locomotor exercise in acute hypoxia (AH).
Seven recreationally active participants performed identical bouts of constant-load cycling (131 ± 39 W, 10.1 ± 1.4 min) on three occasions: (i) in normoxia (N, PI O2 , 147.1 mmHg); (ii) in AH (FI O2 , 0.105; PI O2 , 73.8 mmHg); and (iii) after 14 days in CH (5260 m; PI O2 , 75.7 mmHg). Throughout trials, prefrontal-cortex tissue oxygenation and middle cerebral artery blood velocity (MCAV) were assessed using near-infrared-spectroscopy and transcranial Doppler sonography. Pre- and post-exercise twitch responses to femoral nerve stimulation and transcranial magnetic stimulation were obtained to assess neuromuscular and corticospinal function.
In AH, prefrontal oxygenation declined at rest (Δ7 ± 5%) and end-exercise (Δ26 ± 13%) (P < 0.01); the degree of deoxygenation in AH was greater than N and CH (P < 0.05). The cerebral O2 delivery index (MCAV × Ca O2 ) was 19 ± 14% lower during the final minute of exercise in AH compared to N (P = 0.013) and 20 ± 12% lower compared to CH (P = 0.040). Maximum voluntary and potentiated twitch force were decreased below baseline after exercise in AH and CH, but not N. Cortical voluntary activation decreased below baseline after exercise in AH (Δ11%, P = 0.014), but not CH (Δ6%, P = 0.174) or N (Δ4%, P = 0.298). A twofold greater increase in motor-evoked potential amplitude was evident after exercise in CH compared to AH and N.
These data indicate that exacerbated supraspinal fatigue after exercise in AH is attenuated after 14 days of acclimatization to altitude. The reduced development of supraspinal fatigue in CH may have been attributable to increased corticospinal excitability, consequent to an increased cerebral O2 delivery.
我们研究了慢性低氧（CH）适应是否会减弱急性低氧（AH）后运动引起的中枢疲劳程度。
7 名有规律运动的参与者在三种情况下进行了相同的恒负荷骑行运动（131 ± 39 W，10.1 ± 1.4 min）：（i）在常氧（N，PI O2 ，147.1 mmHg）；（ii）在 AH（FI O2 ，0.105；PI O2 ，73.8 mmHg）；（iii）在 CH（5260 m，PI O2 ，75.7 mmHg）适应 14 天后。在整个试验过程中，使用近红外光谱和经颅多普勒超声评估前额皮质组织氧合和大脑中动脉血流速度（MCAV）。在运动前和运动后获取股神经刺激和经颅磁刺激的 twitch 反应，以评估神经肌肉和皮质脊髓功能。
在 AH 中，静息时（Δ7 ± 5%）和运动结束时（Δ26 ± 13%）前额氧合下降（P < 0.01）；AH 中的缺氧程度大于 N 和 CH（P < 0.05）。与 N 相比，AH 运动最后 1 分钟的脑氧输送指数（MCAV × Ca O2 ）降低了 19 ± 14%（P = 0.013），与 CH 相比降低了 20 ± 12%（P = 0.040）。AH 和 CH 运动后最大自主和增强 twitch 力低于基线，但 N 则不然。AH 运动后皮质自主激活低于基线（Δ11%，P = 0.014），但 CH（Δ6%，P = 0.174）或 N（Δ4%，P = 0.298）则不然。与 AH 和 N 相比，CH 运动后运动诱发电位幅度增加了两倍。
这些数据表明，在适应高海拔 14 天后，AH 运动后中枢疲劳加剧的现象得到了缓解。CH 中中枢疲劳程度降低可能归因于皮质脊髓兴奋性增加，这是由于脑氧输送增加所致。
