Cain S M
Department of Physiology and Biophysics, University of Alabama at Birmingham 35294-0005.
Med Sci Sports Exerc. 1995 Jan;27(1):60-4.
The symposium, "Mechanisms Which Control VO2 Near VO2max," led to a general agreement that there is a variable impediment to the movement of O2 from the interior of the red cell to the interior of the mitochondrion. By changing the variables associated with O2 delivery or by altering the conditions for muscle contractions, the effective O2 diffusing capacity for muscle can be altered as well. Because it is often measured as the ratio of VO2/PvO2, it was suggested that this be referred to as O2 conductance rather than diffusing capacity. In contrast to the wide range of O2 conductance values found by the symposium contributors, a very narrow range of O2 extraction values was found when VO2 was graphed against O2 delivery. The only experimental values that departed from this relationship to any degree were those where hemoglobin function was altered or if blood flow was forced to extraordinary high levels by a pump. The limits for VO2 in contracting isolated muscle are set not only by O2 supply but by O2 demand associated with stimulus patterns. Other intriguing and perhaps useful questions are: 1) What is the relative contribution of such factors as diffusional shunting, flow heterogeneity, red cell transit time, etc., to the apparent O2 conductance? 2) How is blood flow to contracting muscle controlled? 3) How is contractile force adjusted to energy supply?
题为“VO₂max附近VO₂的控制机制”的研讨会达成了一项普遍共识，即氧气从红细胞内部向线粒体内部移动存在可变阻碍。通过改变与氧气输送相关的变量或改变肌肉收缩的条件，肌肉的有效氧气扩散能力也会改变。由于它通常被测量为VO₂/PvO₂的比值，有人建议将其称为氧气传导率而非扩散能力。与研讨会参与者发现的广泛的氧气传导率值形成对比的是，当将VO₂与氧气输送作图时，发现氧气摄取值的范围非常狭窄。唯一在一定程度上偏离这种关系的实验值是那些血红蛋白功能改变或通过泵使血流被迫达到极高水平的情况。收缩的离体肌肉中VO₂的极限不仅由氧气供应设定，还由与刺激模式相关的氧气需求设定。其他有趣且可能有用的问题是：1）诸如扩散分流、血流异质性、红细胞通过时间等因素对表观氧气传导率的相对贡献是什么？2）收缩肌肉的血流是如何控制的？3）收缩力如何根据能量供应进行调节？
