Enhanced muscle pump during mild dynamic leg exercise inhibits sympathetic vasomotor outflow.
Enhanced muscle pump during mild dynamic leg exercise inhibits sympathetic vasomotor outflow.
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DOI：
10.14814/phy2.12070
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发表时间：
2014-07-16
影响因子：
2.5
通讯作者：
Ogoh S
中科院分区：
文献类型：
--
作者：
Katayama K;Ishida K;Saito M;Koike T;Hirasawa A;Ogoh S
尽管中枢指令和运动加压反射被激活，但肌肉交感神经活动(MSNA)在低强度和中等强度的腿部自行车运动中并没有增加。我们确定了增加中心血容量和负荷心肺压力感受器是否在腿部自行车运动中调节交感血管运动流出。为此，我们改变了踏板频率，以增强骨骼肌泵。受试者分别以60和80rpm的不同踏板速度进行两次腿部循环练习(60EX和80EX试验)，两种情况下(使用和不使用MSNA测量)。在每个试验中，受试者在不同的工作负荷下完成腿部自行车，以保持恒定的氧气消耗(VO2)。通过肘部右侧正中神经的显微神经描记记录MSNA。在没有MSNA测量的情况下，使用心阻抗图无创地测量胸阻抗、每搏量(SV)和心输出量(CO)。在60EX和80EX试验中，锻炼期间的心率和VO2没有差异。在80EX试验期间胸阻抗、SV和CO的变化比60EX试验期间更大。在60EX试验中，MSNA与安静时相比没有变化(25.8±3.1[安静]至28.3±3.4[运动]脉冲/分钟)，而在80EX试验中，MSNA显著下降(25.8±2.8[休息]至19.7±2.0[运动]脉冲/分钟)。这些结果表明，肌泵引起的中心血容量增加，从而使心肺压力感受器负荷增加，可以在轻度动态腿部运动中抑制交感血管运动流出，尽管激活了中枢指令和运动加压反射。通过增加踏板频率来调节中心血容量，可降低腿部骑行时的肌交感神经活动。这一结果表明，在维持动脉血压的轻度和轻度动态腿部运动中，交感血管运动流出强烈地受到心肺压力感受器负荷的影响。
Muscle sympathetic nerve activity (MSNA) is not increased during leg cycling at light and mild intensities, despite activation of central command and the exercise pressor reflex. We determined whether increasing central blood volume and loading the cardiopulmonary baroreceptors modulate sympathetic vasomotor outflow during leg cycling. To this end, we changed the pedaling frequency to enhance skeletal muscle pump. Subjects performed two leg cycle exercises at differential pedal rates of 60 and 80 rpm (60EX and 80EX trials) for two conditions (with and without MSNA measurement). In each trial, subjects completed leg cycling with a differential workload to maintain constant oxygen consumption (VO2). MSNA was recorded via microneurography at the right median nerve of the elbow. Without MSNA measurement, thoracic impedance, stroke volume (SV), and cardiac output (CO) were measured non‐invasively using impedance cardiography. Heart rate and VO2 during exercise did not differ between the 60EX and 80EX trials. Changes in thoracic impedance, SV, and CO during the 80EX trial were greater than during the 60EX trial. MSNA during the 60EX trial was unchanged compared with that at rest (25.8 ± 3.1 [rest] to 28.3 ± 3.4 [exercise] bursts/min), whereas a significant decrease in MSNA was observed during the 80EX trial (25.8 ± 2.8 [rest] to 19.7 ± 2.0 [exercise] bursts/min). These results suggest that a muscle pump‐induced increase in central blood volume, and thereby loading of cardiopulmonary baroreceptors, could inhibit sympathetic vasomotor outflow during mild dynamic leg exercise, despite activation of central command and the exercise pressor reflex. Muscle sympathetic nerve activity during leg cycling was reduced when central blood volume was manipulated by increasing the pedaling frequency. This result suggest that sympathetic vasomotor outflow is strongly affected by loading of cardiopulmonary baroreceptors at light and mild dynamic leg exercise to maintain arterial blood pressure.