Abstract
Leg immersion in carbonated water improves endothelial‐mediated vasodilator function and decreases arterial stiffness but the mechanism underlying this effect remains poorly defined. We hypothesized that carbonated water immersion increases muscle blood flow. To test this hypothesis, 10 men (age 21 ± 0 years; mean ± SD) underwent lower leg immersion in tap or carbonated water at 38°C. We evaluated gastrocnemius muscle oxyhemoglobin concentration and tissue oxygenation index using near‐infrared spectroscopy, skin blood flow by laser Doppler flowmetry, and popliteal artery (PA) blood flow by duplex ultrasound. Immersion in carbonated, but not tap water elevated PA (from 38 ± 14 to 83 ± 31 mL/min; P < 0.001) and skin blood flow (by 779 ± 312%, P < 0.001). In contrast, lower leg immersion elevated oxyhemoglobin concentration and tissue oxygenation index with no effect of carbonation (P = 0.529 and P = 0.495). In addition, the change in PA blood flow in response to immersion in carbonated water correlated with those of skin blood flow (P = 0.005) but not oxyhemoglobin concentration (P = 0.765) and tissue oxygenation index (P = 0.136) while no relations was found for tap water immersion. These findings indicate that water carbonation has minimal effect on muscle blood flow. Furthermore, PA blood flow increases in response to lower leg immersion in carbonated water likely due to a large increase in skin blood flow.
Highlights
Thermal therapy such as sauna therapy may be a therapeutic option for patients with hypertension, chronic heart failure, and coronary artery disease (Imamura et al 2001; Kihara et al 2002, 2009; Miyata et al 2008)
near-infrared spectroscopy (NIRS)-determined HbO2 (P = 0.012) and Tissue oxygenation index (TOI) (P = 0.004) of the gastrocnemius muscle increased during immersion in both tap and carbonated water and the change was similar for the two conditions (P = 0.477 and P = 0.115 respectively)
The carbonated water-induced increase in popliteal artery (PA) blood flow correlated with changes in skin blood flow (SkBF) (P = 0.005, Fig. 2) and Cutaneous vascular conductance (CVC) (P = 0.006) but not Hemodynamic Heart rate Mean arterial pressure Stroke volume Cardiac output (L/min) SkBF (AU) CVC (AU/mmHg) Tsk (°C) VAShot
Summary
Thermal therapy (heating) such as sauna therapy may be a therapeutic option for patients with hypertension, chronic heart failure, and coronary artery disease (Imamura et al 2001; Kihara et al 2002, 2009; Miyata et al 2008). Acute leg heating at 45°C for 20 min improves endothelial function and reduces oxidative stress in patients with chronic heart failure (Inoue et al 2012). Acute leg heating may be harmful in patients with cardiovascular disease despite its beneficial effect on endothelial function. Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society.
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