Ideas about control of skeletal and cardiac muscle blood flow (1876-2003): cycles of revision and new vision

This perspective examines origins of some key ideas central to major issues to be addressed in five subsequent mini-reviews related to Skeletal and Cardiac Muscle Blood Flow. The questions discussed are as follows. 1) What causes vasodilation in skeletal and cardiac muscle and 2) might the mechanisms be the same in both? 3) How important is muscle's mechanical contribution (via muscle pumping) to muscle blood flow, including its effect on cardiac output? 4) Is neural (vasoconstrictor) control of muscle vascular conductance and muscle blood flow significantly blunted in exercise by muscle metabolites and what might be a dominant site of action? 5) What reflexes initiate neural control of muscle vascular conductance so as to maintain arterial pressure at its baroreflex operating point during dynamic exercise, or is muscle blood flow regulated so as to prevent accumulation of metabolites and an ensuing muscle chemoreflex or both?