Intermittent exercise abolishes the diurnal variation in endothelial-dependent flow-mediated dilation in humans

exercise abolishes the diurnal variation in endothelial-dependent flow-mediated dilation in humans. Am J Physiol Regul Integr Comp Physiol 298: R427–R432, 2010. First published November 18, 2009; doi:10.1152/ajpregu.00442.2009.—It is currently unclear to what extent diurnal variation and exercise effect endothelium-dependent nitric oxide (NO)-mediated vasodilation. Therefore, we measured brachial artery flow-mediated dilation (FMD) in 10 males (mean age 28 yr, SD 7), before and after a bout of intermittent cycling at 70 % peak oxygen uptake on separate days beginning either at 0800 or 1600. Edge-detection and wall-tracking software was used to measure changes in arterial diameter, while shear rate (SR) was assessed using simultaneously derived blood flow velocity and B-mode diameter data. The FMD data were analyzed before and after normalization for SR with repeated-measures models. Before exer-cise, mean SD FMD was 7 3 % in the morning compared wit