Black men have attenuated increases in forearm vascular conductance (FVC) and forearm blood flow (FBF) during moderate and high-intensity rhythmic handgrip exercise compared with White men, but the underlying mechanisms are unclear. Here, we tested for the first time the hypothesis that functional sympatholysis (i.e., attenuation of sympathetic vasoconstriction in the exercising muscles) is impaired in Black men compared with White men. Thirteen White and fourteen Black healthy young men were studied. FBF (duplex Doppler ultrasound), and mean arterial pressure (MAP, Finometer) were measured at rest and during rhythmic handgrip exercise at 30% maximal voluntary contraction. FVC was calculated as FBF/MAP. Sympathetic activation was induced via lower body negative pressure (LBNP) at -20 Torr for 2 min at rest and from the 3^rd to the 5^th min of handgrip. Sympathetic vasoconstriction was assessed as percent reductions in FVC during LBNP. The groups presented similar resting FVC, FBF, and MAP. During LBNP at rest, reductions in FVC were not different between White (-35 ± 10%) and Black men (-32 ± 14%; P = 0.616), indicating similar reflex-induced sympathetic vasoconstriction. During handgrip exercise, there were minimal reductions in FVC with LBNP in either group (White: -1 ± 7%, Black: +1 ± 8%; P = 0.523), indicating functional sympatholysis in both groups. Thus, contrary to our hypothesis, our findings indicate a preserved functional sympatholysis in healthy young Black men compared with White men, suggesting that this mechanism does not appear to contribute to reduced exercise hyperemia during moderate-intensity rhythmic handgrip in this population.

中文翻译：

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在有节奏的握力运动期间，健康的年轻黑人男性保留了功能性交感神经溶解。

与白人男性相比，黑人男性在中等强度和高强度有节奏的握力运动中前臂血管传导 (FVC) 和前臂血流量 (FBF) 的增加减弱，但潜在机制尚不清楚。在这里，我们首次测试了与白人男性相比，黑人男性的功能性交感神经溶解（即运动肌肉中交感神经血管收缩减弱）受损的假设。研究了十三名白人和十四名黑人健康的年轻人。FBF（双工多普勒超声）和平均动脉压（MAP，Finometer）在休息和有节奏的握力运动期间以 30% 的最大自主收缩进行测量。FVC 计算为 FBF/MAP。交感神经激活经由下体负压（LBNP）在-20乇在休息和从3诱导2分钟^RD到 5^日最小把手。交感神经血管收缩被评估为 LBNP 期间 FVC 的减少百分比。各组呈现相似的静息 FVC、FBF 和 MAP。在休息 LBNP 期间，白人 (-35 ± 10%) 和黑人男性 (-32 ± 14%；P = 0.616) 的 FVC 减少没有差异，表明类似的反射引起的交感神经血管收缩。在握力运动期间，任何一组 LBNP 的 FVC 都有最小的降低（白色：-1 ± 7%，黑色：+1 ± 8%；P = 0.523），表明两组都有功能性交感神经溶解。因此，与我们的假设相反，我们的研究结果表明，与白人男性相比，健康的年轻黑人男性保留了功能性交感神经溶解，这表明这种机制似乎不会导致该人群在中等强度有节奏的握力期间减少运动充血。