Acute Effects of Short‐term Warm Water Immersion on Vascular Function

Abstract

Cardiovascular disease (CVD) is a leading cause of death in the world. Currently, effective strategies for preventing CVD have been developed extensively. CVD is characterized by vascular dysfunction, including the decreased endothelial-dependent vasodilation and the increased arterial stiffness. In this line, regular physical activity (i.e., aerobic exercise) is one of the most established treatments of the primary prevention of CVD because it may restore impaired vascular function. However, not all populations can engage in physical activities. Thus, substitute interventions on vascular hemodynamics are needed for individuals with physical disabilities. Warm water immersion (WWI) has a potentially favorable effect on vascular health. However; the effects of short-term WWI on vascular function remain unclear. The present study aimed to determine the acute effects of short-term WWI on vascular function in healthy men. Ten healthy men (27-57 years, 44±12 years of mean age) underwent 5-minute WWI (40-41ºC) at the heart level. Heart rate, blood pressure (BP), aortic and leg pulse wave velocity (PWV), and femoral arterial blood flow and shear rate (SS) were measured before and 10 minutes after WWI. After 5-minute WWI, heart rate and brachial diastolic BP were significantly decreased. Aortic and leg PWV were decreased by 7.5% and 3.1%, respectively (P=0.006 and P=0.049). Femoral arterial blood flow was increased by 45.9% (P=0.002) and leg vascular resistance was decreased by 29.1% (P<0.001). Change in leg PWV was significantly correlated with corresponding change in femoral arterial blood flow (r = - 0.713, P = 0.181) and SS (r = - 0.724, P = 0.154). Our results indicate that a short-term WWI acutely improves vascular function. Further studies to determine the interaction between the residual effect of a single bout of short-term WWI and chronic change (e.g., adaptation) in vascular function are needed.