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(Hypertension. 2009;54:278.)
© 2009 American Heart Association, Inc.

Original Articles

Impact of Shear Rate Modulation on Vascular Function in Humans

Toni M. Tinken; Dick H.J. Thijssen; Nicola Hopkins; Mark A. Black; Ellen A. Dawson; Christopher T. Minson; Sean C. Newcomer; M. Harold Laughlin; N. Timothy Cable; Daniel J. Green

From the Research Institute for Sport and Exercise Science (T.M.T., D.H.J.T., N.H., M.A.B., E.A.D., N.T.C., D.J.G.), Liverpool John Moore’s University, Liverpool, United Kingdom; Department of Physiology (D.H.J.T.), Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands; Department of Human Physiology (C.T.M.), University of Oregon, Eugene; Department of Health and Kinesiology (S.C.N.), Purdue University, West Lafayette, Ind; Department of Biomedical Sciences (M.H.L.), University of Missouri, Columbia; and the School of Sport Science, Exercise and Health (D.J.G.), University of Western Australia, Crawley, Western Australia, Australia.

Correspondence to Daniel J. Green, Research Institute for Sport and Exercise Science, Liverpool John Moores University, 15-21 Webster St, Liverpool L3 2ET, United Kingdom. E-mail d.j.green{at}ljmu.ac.uk

Shear stress is an important stimulus to arterial adaptation in response to exercise and training in humans. We recently observed significant reverse arterial flow and shear during exercise and different antegrade/retrograde patterns of shear and flow in response to different types of exercise. The purpose of this study was to simultaneously examine flow-mediated dilation, a largely NO-mediated vasodilator response, in both brachial arteries of healthy young men before and after 30-minute interventions consisting of bilateral forearm heating, recumbent leg cycling, and bilateral handgrip exercise. During each intervention, a cuff inflated to 60 mm Hg was placed on 1 arm to unilaterally manipulate the shear rate stimulus. In the noncuffed arm, antegrade flow and shear increased similarly in response to each intervention (ANOVA; P<0.001, no interaction between interventions; P=0.71). Baseline flow-mediated dilation (4.6%, 6.9%, and 6.7%) increased similarly in response to heating, handgrip, and cycling (8.1%, 10.4%, and 8.9%, ANOVA; P<0.001, no interaction; P=0.89). In contrast, cuffed arm antegrade shear rate was lower than in the noncuffed arm for all of the conditions (P<0.05), and the increase in flow-mediated dilation was abolished in this arm (4.7%, 6.7%, and 6.1%; 2-way ANOVA: all conditions interacted P<0.05). These results suggest that differences in the magnitude of antegrade shear rate transduce differences in endothelial vasodilator function in humans, a finding that may have relevance for the impact of different exercise interventions on vascular adaptation in humans.

Key Words: conduit artery • flow-mediated dilation • exercise training