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Obligatory role of hyperaemia and shear stress in microvascular adaptation to repeated heating in humans
Author(s) -
Green Daniel J.,
Carter Howard H.,
Fitzsimons Matthew G.,
Cable N. Timothy,
Thijssen Dick H.J.,
Naylor Louise H.
Publication year - 2010
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.2010.186965
Subject(s) - hyperaemia , vasodilation , medicine , forearm , cardiology , endothelium , circulatory system , endothelial dysfunction , shear stress , cuff , laser doppler velocimetry , anesthesia , blood flow , surgery , materials science , composite material
The endothelium, a single layer of cells lining the entire circulatory system, plays a key role in maintaining vascular health. Endothelial dysfunction independently predicts cardiovascular events and improvement in endothelial function is associated with decreased vascular risk. Previous studies have suggested that exercise training improves endothelial function in macrovessels, a benefit mediated via repeated episodic increases in shear stress. However, less is known of the effects of shear stress modulation in microvessels. In the present study we examined the hypothesis that repeated skin heating improves cutaneous microvascular vasodilator function via a shear stress‐dependent mechanism. We recruited 10 recreationally active males who underwent bilateral forearm immersion in warm water (42°C), 3 times per week for 30 min. During these immersion sessions, shear stress was manipulated in one arm by inflating a pneumatic cuff to 100 mmHg, whilst the other arm remained uncuffed. Vasodilatation to local heating, a NO‐dependent response assessed using laser Doppler, improved across the 8 week intervention period in the uncuffed arm (cutaneous vascular conductance week 0 vs. week 4 at 41°C: 1.37 ± 0.45 vs. 2.0 ± 0.91 units, P = 0.04; 42°C: 2.06 ± 0.45 vs. 2.68 ± 0.83 units; P = 0.04), whereas no significant changes were evident in the cuffed arm. We conclude that increased blood flow, and the likely attendant increase in shear stress, is a key physiological stimulus for enhancing microvascular vasodilator function in humans.