Acute Exertion Elicits a H 2 O 2 – Dependent Vasodilator Mechanism in the Microvasculature of Exercise Trained but not Sedentary Adults Short Title : Resistance Exercise and Microvascular Function

A erobic exercise promotes a multitude of health benefits , including improving cardiorespiratory fitness and vascular reactivity of large and small arteries. The effects of resistance exercise on cardiovascular function are less well understood, and recent evidence suggests that a single bout of heavy resistance exercise causes prolonged endothe-lial dysfunction in the conduit arteries of sedentary subjects who do not regularly exercise. This is in stark contrast to exercise-trained (ET) individuals, as their large artery endo-thelial function is maintained after partaking in an identical session of heavy resistance exercise. One question that remains unanswered is whether the differential effects of heavy resistance exercise between sedentary and ET subjects extend to arterioles that are responsible for regulating tissue perfusion. Therefore, in this study, we tested the hypothesis that adults who regularly engaged in exercise training are protected from microvascular dysfunction that occurs immediately after heavy resistance exercise compared with sedentary subjects. A primary difference in the cardiovascular response to aerobic and isometric exercise is the strong pressor response that occurs during heavy isometric exercise. Systolic blood pressures >400 mm Hg have been reported in elite weight lifters performing leg bench press exercise. 3 Another question that remains unanswered is whether the difference in the vascular response to weight lifting (WL) between sedentary and ET subjects is because of the effects of high intraluminal pressure on the vascular wall during this pressor response and whether the microvasculature of ET subjects is adapted to function normally after high pressure stress. Therefore, we also tested the hypothesis that the different vas-cular response to WL between ET and sedentary subjects could be recapitulated by exposing microvessels to increased intralumi-nal pressure in the laboratory in the absence of exercise-induced changes in circulating neurohumoral factors that occurs in vivo. Abstract—Brachial artery flow–mediated vasodilation in exercise-trained (ET) individuals is maintained after a single bout of heavy resistance exercise compared with sedentary individuals. The purpose of this study was to determine whether vasodilation is also maintained in the microcirculation of ET individuals. A total of 51 sedentary and ET individuals underwent gluteal subcutaneous fat biopsy before and after performing a single bout of leg press exercise. Adipose arterioles were cannulated in an organ bath, and vasodilation to acetylcholine was assessed±the endothelial nitric oxide inhibitor l-NG-nitroarginine methyl ester, the cyclooxygenase inhibitor indomethacin, or the hydrogen peroxide scavenger polyethylene glycol catalase. Separate vessels (isolated from the same groups) were exposed to …