Local heating of an extremity increases blood flow and vascular shear stress throughout the arterial tree. Local heating acutely improves macrovascular dilator function in the upper limbs of young healthy adults through a shear stress dependent mechanism, but has no such effect in the lower limbs of this age group. The effect of acute limb heating on dilator function within the atherosclerotic prone vasculature of the lower limbs of aged adults is unknown. Therefore, the purpose of this study was to test the hypothesis that acute lower limb heating improves macro- and microvascular dilator function within the leg vasculature of aged adults. Nine young and 9 aged adults immersed their lower limbs at a depth of ~33 cm into a heated (~42 °C) circulated water bath for 45 min. Prior to and 30 min after heating, macro- (flow-mediated dilation) and microvascular (reactive hyperemia) dilator function were assessed in the lower limb, following 5 min of arterial occlusion, via Doppler ultrasound. Compared with pre-heat, macrovascular dilator function was unchanged following heating in young adults (P = 0.6), but was improved in aged adults (P = 0.04). Similarly, microvascular dilator function, as assessed by peak reactive hyperemia, was unchanged following heating in young adults (P = 0.1), but was improved in aged adults (P < 0.01). Taken together, these data suggest that acute lower limb heating improves both macro- and microvascular dilator function in an age dependent manner.
- shear stress
- blood flow
- flow-mediated dilation
- reactive hyperemia
- Copyright © 2016, American Journal of Physiology-Heart and Circulatory Physiology