OPPOSING EFFECTS OF SHEAR-MEDIATED DILATION AND MYOGENIC CONSTRICTION ON ARTERY DIAMETER IN RESPONSE TO HANDGRIP EXERCISE IN HUMANS.

Item does not contain fulltextINTRODUCTION: Whilst the impact of changes in blood flow and shear stress on artery function are well documented, the acute effects of increases in arterial pressure are less well described. The aim of this study was to assess the effect of 30-minutes of elevated blood pressure, in the absence of changes in shear stress or sympathetic nervous system (SNS) activation, on conduit arterial diameter. METHODS: Ten male subjects undertook 3 sessions of 30-minutes unilateral handgrip (HG) exercise at 5, 10 and 15% of maximal voluntary contractile (MVC) strength. Brachial artery shear and flow were measured simultaneously during exercise in the active and contralateral resting, arms. Bilateral brachial artery diameter was simultaneously assessed prior to- and immediately post-exercise. In a second experiment, 6 subjects repeated the 15% MVC condition whilst continuous vascular measurements were collected along with measures of muscle sympathetic nerve activity (MSNA). RESULTS: Unilateral HG exercise at all intensities induced step-wise elevations in blood pressure (P<0.01). Whilst step-wise increases were evident in shear rate in the exercising arm (P