engleski

Can arteries of skeletal muscles act as a circulatory bottleneck during heavy exercise?

It is generally assumed that almost no pressure gradient exists in the aorta and large arteries. This holds truth in rest, but during heavy exercise, when the resistance of arterioles in active skeletal muscles is diminished, the remaining resistance of large and small arteries might become significant and limit the maximal perfusion rate. To describe this idea better, a simplified model of vasculature based on the textbook data on circulation is described. The model suggests that the mean arterial pressure (MAP) acts as a hydrostatic pressure reserve that backups sudden changes in the local flow demands. During exercise, reduced resistance in arterioles changes the pressure profile along the arterial tree, making the pressure gradient along arteries more important and arteries become the circulatory bottleneck. Adequately high MAP and the shear stress arterial dilatation are both needed to allow sufficient flow through them. For a normal adult person, the model predicts that a hydrostatic pressure reserve allows almost sixfold increases in arterial flow before it is exhausted. A reduced resistance in arteries (shorter, more elastic arteries) can be expected in a young person, while in an atherosclerotic hypertensive person, reduced hydrostatic pressure reserve and the shear stress responsiveness would compromise the skeletal muscle performance during exercise.

vascular resistance; model; arterial circulation

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