Muscle deoxygenation as related to work rate
Muscle deoxygenation as related to work rate
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DOI：
10.1097/00005768-200210000-00013
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发表时间：
2002-10-01
期刊：
影响因子：
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通讯作者：
Wasserman, K
中科院分区：
文献类型：
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作者：
Chuang, ML;Ting, H;Wasserman, K
目的：在乳酸酸中毒阈值（LAT）以下的恒定的工作率运动的静脉0，内容的减少的动力学是非常迅速的，达到一个恒定值约1分钟。然而，对于LAT以上的工作率，静脉O2含量发生缓慢的进一步减少，这是由于玻尔效应，而不是进一步减少在毛细血管末端PO 2。我们假设相似的差异。当用近红外光谱法（NIRS）研究时，将在肌肉脱氧动力学中观察到关于LAT。研究方法：12名正常人进行了三个恒定的工作率测试，从卸载循环在60%的LAT，80%的LAT，每个重复四次，并在LAT（LAT + 35%之间的LAT和（V）超过dotO（2 max））三次，在一个周期测力计为6分钟。我们测量组织脱氧与近红外光谱仪，在股外侧肌的探头，时间平均的重复。通过呼吸和心跳测量气体交换和心率（HR）。结果：在60%和80% LAT工作率下，组织脱氧动力学在dotO（2）和HR上明显快于（V）。通过1分钟的运动，脱氧是恒定的工作率低于LAT。在30秒时，组织脱氧完成70-95%，而（V）超过dotO（2）和HR仅完成30-60%。对于高于LAT的工作速率，在6分钟的运动期间没有达到肌肉脱氧的稳定状态。1分钟后，上述LAT运动，两种模式之一的缓慢变化的组织氧合发展，脱氧或复氧。据推测，这些不同的反应可能是由于运动乳酸酸中毒的影响。H+伴随乳酸的增加可能由于玻尔效应引起进一步的脱氧，酸中毒引起的血管舒张可能在初始脱氧后引起再氧合。结论：1）在所研究的所有工作速率下，组织脱氧动力学明显快于（V）dotO（2）和HR动力学。和2）低于LAT的1分钟恒定功率运动可以看到组织脱氧的稳态，但高于LAT的功率运动会延迟很多。
Purpose: The kinetics of the decrease in venous 0, content in response to constant work rate exercise below the lactic acidosis threshold (LAT) is very rapid, reaching a constant value by approximately 1 min. However, for work rates above the LAT, a slow further decrease in venous 02 content takes place that is attributable to the Bohr effect rather than further decrease in end capillary PO2. We hypothesized that similar differences. with respect to the LAT, will be observed in muscle deoxygenation kinetics when studied with near-infrared spectroscopy (NIRS). Methods: Twelve normal subjects performed three constant work rate tests from unloaded cycling at 60% of LAT, 80% LAT, each with four repetitions, and above LAT (LAT + 35% between LAT and (V)over dotO(2max)) three times, on a cycle ergometer for 6 min. We measured tissue deoxygenation with NIRS, with the probe over the vastus lateralis muscle, time-averaging the repetitions. Gas exchange and heart rate (HR) were measured breath-by-breath and beat-by-beat. Results: Tissue deoxygenation kinetics were significantly faster than (V)over dotO(2) and HR at 60%- and 80%-LAT work rates. By I min of exercise, deoxygenation was constant for the work rate below the LAT. At 30 s tissue deoxygenation was 70-95% complete, whereas (V)over dotO(2) and HR were only 30-60% complete. For the work rate above the LAT, a steady state for muscle deoxygenation was not reached during the 6 min of exercise. After I min of above-LAT exercise, either one of two patterns of slow change in tissue oxygenation developed, deoxygenation or reoxygenation. It is postulated that these different responses might be due to effects of the exercise lactic acidosis. H+ accompanying lactate increase might cause further deoxygenation due to the Bohr effect, and acidosis-induced vasodilatation might cause reoxygenation after the initial deoxygenation. Conclusion: 1) The kinetics of tissue deoxygenation are significantly more rapid than (V)over dotO(2) and HR kinetics at all work rates studied. and 2) steady-state in tissue deoxygenation is seen by I min of constant work rate exercise below the LAT, but this is much delayed for work rates above the LAT.