THE IMPACT OF WINTER SWIMMING ON FUNCTIONAL MICROVASCULAR CHANGES

Objective: Microcirculation plays an important role in the development of cardiovascular control. Therefore, the aim of our study was to investigate the impact of winter swimming on functional changes in cutaneous microcirculation Flow-mediated skin fluorescence (FMSF) is a novel and non-invasive technique assessing microvascular function based on the measurements of nicotinamide adenine dinucleotide hydrogen (NADH) fluorescence intensity in the epidermis and post occlusive reactive hyperemia test. NADH intensity changes in response to blockage and release of blood flow in the brachial artery, which corresponds to microvascular function. Design and method: FMSF examinations were performed before and after the winter swimming period lasting from November 2022 to April 2023 in 37 subjects (mean age 46±4,0 years, 65% women). The mean frequency of winter swimming activity was 1,3 times per week. We analysed the following variables: the ischemic response (IRmax and IRindex) – the ratio of relative to baseline maximal increase in fluorescence intensity during cuff occlusion and the hyperaemic response after cuff release (HRmax and HRindex). Flowmotion, measured at baseline (FM) and at reperfusion (FM(R)), reflects flow oscillations. Normoxia oscillatory index (NOI) represents the proportion of endothelial and neurogenic blood flow oscillations in relation to all oscillations detected in low frequency range. The hypoxia sensitivity (HS), measured during reperfusion, reflects the intensity of flowmotion related to myogenic oscillations. Results: The statistical analysis revealed following results according to the winter swimming: Conclusions: Increase in microvascular oscillations denoted by NOI and HS suggests a beneficial impact of winter swimming on cutaneous microcirculation. Improvement in microcirculation performance may partly explain lowering of cardiovascular risk in regular winter swimmers.