Skin Microvascular Reactivity in Young Adults in Relation to Maximal and Submaximal Indices of Cardiorespiratory Fitness

Abstract

Low cardiorespiratory fitness (CRF) is associated with endothelial dysfunction and decreased microvascular reactivity that increases risk for cardiovascular disease. Enhanced endothelial functioning is associated with CRF, specifically maximal aerobic capacity. However, the effect of submaximal indices of CRF, such as ventilatory threshold (VT) and respiratory compensation point (RCP), on microvascular reactivity is unclear. PURPOSE: To determine the association between maximal and submaximal indices of CRF and skin microvascular reactivity in physically active, untrained young adults. METHODS: Twenty-six physically active, untrained, young adults (21.6 ±1.9 yrs, 73.3 ±10.5 kg, BMI 23.7 ±2.9 kg.m2) were recruited. An incremental bicycle ergometer test was then performed to determine VO2peak, VT and RCP. One week later, a post-occlusive reactive hyperemia response (PORH) test was used to assess microvascular reactivity on the subject’s right palmer forearm using a moorVMS-Laser Doppler Fluxmeter (LDF). Defined flux and time parameters were calculated from the PORH test including PORHmax (maximum increase in hyperemia perfusion above resting flux), PORHpeak (amplitude of peak perfusion), time-to-peak perfusion (Tp) and the ratio of PORHmax/Tp. Multiple linear regression (backward method) was used to determine the association between variables. Significance was set at P<0.05. RESULTS: The results for VO2peak (46.65 ± 7.48 ml/kg.min-1), VT (34.67 ± 12.62 % of VO2peak) and RCP (74.88 ± 19 % of VO2peak) indicated a moderate maximal aerobic capacity but low submaximal endurance capacity for the participants. Maximal and submaximal CRF indices were shown to be strongly associated with microvascular reactivity. Specifically, VO2peak was shown to be the best predictor of PORHmax (r2 = 0.18; p=0.03). VT was shown to be the best predictor of PORHpeak (r2 = 0.17; p=0.04), TP (r2 = 0.11; P=0.04) and PORHmax/ TP (r2 = 0.18; P=0.02). RCP together with VT predicted 28% of the variance in PORHmax/ TP (r2 = 0.28; P=0.02) CONCLUSION: Maximal and submaximal indices of cardiorespiratory fitness, specifically VO2 peak and VT are independent predictors of microvascular reactivity. The finding that VT, a submaximal index of cardiorespiratory fitness, predicts most microvascular reactivity parameters has implications for exercise interventions aimed at improving microvascular health and reducing cardiovascular risk.