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首页> 外文期刊>American Journal of Physiology >Mechanical effects of muscle contraction do not blunt sympathetic vasoconstriction in humans.
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Mechanical effects of muscle contraction do not blunt sympathetic vasoconstriction in humans.

机译：肌肉收缩的机械作用不会使人的交感血管收缩变钝。

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Sympathetic vasoconstrictor responses are blunted in the vascular beds of contracting muscle (functional sympatholysis), but the mechanism(s) have been difficult to elucidate. We tested the hypothesis that the mechanical effects of muscle contraction blunt sympathetic vasoconstriction in human muscle. We measured forearm blood flow (Doppler ultrasound) and calculated the reductions in forearm vascular conductance (FVC) in response to reflex increases in sympathetic activity evoked via lower body negative pressure (LBNP). In protocol 1, eight young adults were studied under control resting conditions and during simulated muscle contractions using rhythmic forearm cuff inflations (20 inflations/min) with cuff pressures of 50 and 100 mmHg with the arm below heart level (BH), as well as 100 mmHg with the arm at heart level (HL). Forearm vasoconstrictor responses (%DeltaFVC) during LBNP were -26 +/- 2% during control conditions and were not blunted by simulated contractions (range = -31 +/- 3% to -43 +/- 6%). In protocol 2, eight subjects were studied under control conditions and during rhythmic handgrip exercise (20 contractions/min) using workloads of 15% maximum voluntary contraction (MVC) at HL and BH (similar metabolic demand, greater mechanical muscle pump effect for the latter) and 5% MVC BH alone and in combination with superimposed forearm compressions of 100 mmHg (similar metabolic demand, greater mechanical component of contractions for the latter). The forearm vasoconstrictor responses during LBNP were blunted during 15% MVC exercise with the arm at HL (-1 +/- 3%) and BH (-2 +/- 3%) compared with control (-25 +/- 3%; both P < 0.005) but were intact during both 5% MVC alone (-24 +/- 4%) and with superimposed compressions (-23 +/- 4%). We conclude that mechanical effects of contraction per se do not cause functional sympatholysis in the human forearm and that this phenomenon appears to be coupled with the metabolic demand of contracting skeletal muscle.
机译：交感性血管收缩反应在收缩肌肉的血管床中变钝（功能性交感神经），但机制尚难以阐明。我们检验了肌肉收缩的机械作用钝化人肌肉中交感性血管收缩的假说。我们测量了前臂的血流量（多普勒超声），并计算了由于下体负压（LBNP）引起的交感神经活动反射性增加，前臂血管电导率（FVC）的降低。在方案1中，研究了八名年轻人在控制的休息条件下以及在模拟的肌肉收缩过程中，使用有节奏的前臂袖带充气（20充气/分钟），袖带压力分别为50和100 mmHg，手臂低于心脏水平（BH），以及手臂处于心脏水平（HL）时为100 mmHg。在对照条件下，LBNP期间的前臂血管收缩反应（％DeltaFVC）为-26 +/- 2％，并且不受模拟收缩的影响（范围= -31 +/- 3％至-43 +/- 6％）。在方案2中，研究了八名受试者在控制条件下和节律性握力锻炼期间（每分钟20次收缩），使用HL和BH时最大自愿收缩（MVC）的工作量为15％（相似的新陈代谢需求，后者对后者的机械肌肉泵作用更大） ）和5％的MVC BH单独使用，并与100 mmHg的前臂叠加加压相结合（相似的代谢需求，后者的收缩机械成分更大）。在15％MVC运动期间，与对照组（-25 +/- 3％）相比，手臂处于HL（-1 +/- 3％）和BH（-2 +/- 3％）时，LBNP期间的前臂血管收缩反应减弱。两者均P <0.005），但在5％MVC（-24 +/- 4％）和叠加压缩（-23 +/- 4％）期间均完整。我们得出结论，收缩本身的机械作用不会在人类前臂中引起功能性交感神经，并且这种现象似乎与收缩骨骼肌的代谢需求有关。

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