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 unilateral 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 changes in both the immobilized and non-immobilized limbs and the changes were greater in magnitude in the immobilized limb. 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.