Hicks A, McGill S, Hughson R L
Department of Kinesiology, University of Waterloo, Waterloo, ON N2L 3G1 Canada.
Can J Appl Physiol. 1999 Jun;24(3):216-30. doi: 10.1139/h99-018.
The relationship between tissue oxygenation measured by near-infrared spectroscopy (NIRS) and forearm muscle blood flow (FBF) measured by Doppler ultrasound was tested during isometric contractions at 10 and 30% maximal voluntary contraction (MVC) under conditions of normoxia and hypoxia (14% inspired O2). Six subjects maintained contractions at 10% MVC for 5 min and 30% for 2 min in both gas conditions. FBF was elevated during exercise at 10% MVC in hypoxia compared to normoxia, but there was no further increase in flow at 30% MVC. Median power frequency calculations from electromyographic recordings suggested progressive development of fatigue throughout both 10 and 30% MVC contractions. NIRS indicated no change in muscle oxygenation at 10% MVC, but deep venous blood O2 saturation was reduced in normoxia and more so in hypoxia. At 30% MVC, both NIRS and venous O2 saturation were reduced, with no effect of hypoxia on the NIRS signal. While NIRS might provide an indication of muscle oxygenation during isometric exercise, the conflicting findings for NIRS and direct venous blood sampling at 10 vs 30% MVC suggest caution in the application of this noninvasive technique.
在常氧和低氧（吸入氧浓度为14%）条件下，通过近红外光谱（NIRS）测量的组织氧合与通过多普勒超声测量的前臂肌肉血流量（FBF）之间的关系，在10%和30%最大自主收缩（MVC）的等长收缩过程中进行了测试。六名受试者在两种气体条件下，分别以10%MVC收缩5分钟和30%MVC收缩2分钟。与常氧相比，低氧条件下10%MVC运动期间FBF升高，但30%MVC时血流量没有进一步增加。肌电图记录的中位功率频率计算表明，在10%和30%MVC收缩过程中疲劳逐渐发展。NIRS显示10%MVC时肌肉氧合无变化，但常氧下深静脉血氧饱和度降低，低氧时更明显。在30%MVC时，NIRS和静脉血氧饱和度均降低，低氧对NIRS信号无影响。虽然NIRS可能为等长运动期间的肌肉氧合提供一个指标，但在10%与30%MVC时NIRS与直接静脉血采样的矛盾结果表明，在应用这种非侵入性技术时应谨慎。
