Short-term unilateral leg immobilization alters peripheral but not central arterial structure and function in healthy young humans.

Short-term leg immobilization is an acute model of inactivity, which induces vascular deconditioning. The present study was conducted to determine if short-term leg immobilization induced alterations in central and peripheral conduit artery structure (diameter and compliance), function (resting blood flow and mean wall shear rate), and peripheral flow-mediated dilation. Healthy participants (n = 7 women and n = 8 men) were studied before and after 12 days of unilateral leg immobilization. Carotid artery structure and function were unaltered with immobilization indicating that the unilateral immobilization did not have a detectable effect on this representative central artery. In contrast, peripheral measures of arterial structure at the common femoral and popliteal arteries showed significant reductions in both the immobilized and non-immobilized limbs but to a greater extent in the immobilized limbs. Specifically, femoral and popliteal artery compliance and femoral artery diameter were reduced in both the immobilized and the non-immobilized limb (p < 0.05) while popliteal artery diameter was reduced only in the immobilized leg. Popliteal artery flow-mediated dilation, an indicator of peripheral artery function, was increased in the immobilized limb, which parallels reports in paralyzed limbs of spinal-cord-injured individuals. The time course of vascular alterations with inactivity likely follows a sequence of adaptations in arterial structure and function reflecting differing initial flow patterns, and arterial wall composition, and diverse hemodynamic stimuli within different blood vessels.