Secher Niels H, Volianitis Stefanos
The Copenhagen Muscle Research Center, Department of Anesthesia, Rigshospitalet, University of Copenhagen, Denmark.
Med Sci Sports Exerc. 2006 Oct;38(10):1797-803. doi: 10.1249/01.mss.0000230343.64000.ac.
Oxygen transport to working skeletal muscles is challenged during whole-body exercise. In general, arm-cranking exercise elicits a maximal oxygen uptake (VO2max) corresponding to approximately 70% of the value reached during leg exercise. However, in arm-trained subjects such as rowers, cross-country skiers, and swimmers, the arm VO2max approaches or surpasses the leg value. Despite this similarity between arm and leg VO2max, when arm exercise is added to leg exercise, VO2max is not markedly elevated, which suggests a central or cardiac limitation. In fact, when intense arm exercise is added to leg exercise, leg blood flow at a given work rate is approximately 10% less than during leg exercise alone. Similarly, when intense leg exercise is added to arm exercise, arm blood flow and muscle oxygenation are reduced by approximately 10%. Such reductions in regional blood flow are mainly attributed to peripheral vasoconstriction induced by the arterial baroreflex to support the prevailing blood pressure. This putative mechanism is also demonstrated when the ability to increase cardiac output is compromised; during exercise, the prevailing blood pressure is established primarily by an increase in cardiac output, but if the contribution of the cardiac output is not sufficient to maintain the preset blood pressure, the arterial baroreflex increases peripheral resistance by augmenting sympathetic activity and restricting blood flow to working skeletal muscles.
在全身运动期间，输送到工作中的骨骼肌的氧气会受到挑战。一般来说，手摇臂运动所引发的最大摄氧量（VO₂max）约为腿部运动时所达到值的70%。然而，在诸如划船运动员、越野滑雪者和游泳运动员等上肢训练有素的受试者中，上肢VO₂max接近或超过下肢的值。尽管上肢和下肢的VO₂max存在这种相似性，但当在上肢运动基础上增加下肢运动时，VO₂max并未显著升高，这表明存在中枢或心脏方面的限制。事实上，当在上肢运动基础上增加高强度下肢运动时，在给定工作强度下的下肢血流量比单独进行下肢运动时减少约10%。同样，当在上肢运动基础上增加高强度下肢运动时，上肢血流量和肌肉氧合作用会减少约10%。局部血流量的这种减少主要归因于动脉压力反射引起的外周血管收缩，以维持当时的血压。当增加心输出量的能力受损时，也会出现这种假定的机制；在运动过程中，当时的血压主要通过心输出量的增加来维持，但如果心输出量的贡献不足以维持预设血压，动脉压力反射会通过增强交感神经活动和限制流向工作中的骨骼肌的血流量来增加外周阻力。
