Three hours of targeted limb passive heating increases conduit artery shear rates and lowers vascular stiffness

Cardiovascular disease remains the leading cause of mortality, primarily driven by endothelial dysfunction, which is initiated by risk factors that provoke pathological changes in endothelial function. Limb passive heating (LPH) elevates shear rate to levels comparable to mild exercise, whereby previous data has shown 38°C to be thermally comfortable. This study investigates the responses of peripheral and central arteries, as well as whole-body and local thermal comfort during 3 h of LPH applied simultaneously to all four limbs at a skin temperature of 38°C. To achieve this, local arm and leg thermal comfort was assessed, alongside shear rate measurements in the brachial and superficial femoral arteries, as well as the ascending aortic arch at baseline and at consecutive time points throughout the 3-h LPH exposure. Shear rate increased significantly in the brachial arteries (p = 0.0005) and superficial femoral arteries (p < 0.0001) after 3-h LPH exposure. LPH did not significantly affect shear rate levels in the ascending aortic arch. With thermal comfort reaching 9 ± 1, the 3-h LPH exposure was tolerable but represented the maximum limit of thermal intensity. Vascular stiffness, measured through peripheral pulse wave velocity, was significantly reduced (p = 0.049). This approach may serve as a suitable chronic therapeutic intervention to complement other lifestyle behaviors to improve systemic vascular stiffness and vascular function.