Muscle Pump and Chemical Dilation in Exercise Hyperemia

肌肉泵的机械效应和动脉血管舒张被认为是运动性充血的两个重要决定因素。两者对人类运动充血的作用尚不清楚。此外，化学诱导的扩张（如代谢物）和机械因素在决定运动性充血中的可能相互作用尚未确定。本实验旨在确定1)增加静息前臂血流量是否会改变单次机械压迫或自主收缩时的充血反应；2)增加静息前臂血流量是否会改变稳态运动或有节奏的机械压迫时的充血反应；3)内皮源性血管扩张剂是否有助于单次肌肉收缩或机械压迫时的充血反应。这种独特的方法将测量前臂充血到压缩或收缩的三个不同水平的“静息”血流。大多数关于运动充血的研究都集中在单一因素的作用上，而不是机制如何相互作用。所提出的实验的优势在于，我们将操纵机械和化学因素，并评估它们在人类急性和稳态运动期间对肌肉血流量的综合影响。

The mechanical effects of the muscle pump and arterial vasodilation are thought to be two important determinants of exercise hyperemia. The contributions of either to exercise hyperemia in humans are not clear. In addition, the possible interactions of chemically induced dilation (e.g. metabolites) and mechanical factors in determining exercise hyperemia have not been determined. The proposed experiments are designed to determine 1) whether increasing resting forearm blood flow alters the hyperemic response to a single mechanical compression or voluntary contraction, 2) whether increasing resting forearm blood flow alters the hyperemic responses to steady state exercise or rhythmic mechanical compression, and 3) whether endothelium-derived vasodilators contribute to the hyperemic response of a single muscle contraction or mechanical compression. This unique approach will measure forearm hyperemia to compression or contraction at three different levels of "resting" blood flow. Most studies of exercise hyperemia focus on the contribution of a single factor, rather than how mechanisms interact. The strength of the proposed experiments is that we will manipulate both mechanical and chemical factors and assess their combined effects on muscle blood flow during acute and steady state exercise in humans.