Vianna Lauro C, Araújo Claudio Gil S, Fisher James P
School of Sport and Exercise Sciences, Univ. of Birmingham, Edgbaston, Birmingham B15 2TT, UK.
J Appl Physiol (1985). 2009 Oct;107(4):1113-20. doi: 10.1152/japplphysiol.00480.2009. Epub 2009 Aug 13.
The purpose of the present study was to determine the relative importance of peripheral feedback from mechanically (mechanoreflex) and metabolically (metaboreflex) sensitive muscle afferents and central signals arising from higher centers (central command) to the exercise-induced increases in regional cerebral perfusion. To accomplish this, anterior cerebral artery (ACA) mean blood velocity (V(mean)) responses were assessed during sustained and rhythmic passive calf muscle stretch (mechanoreflex), volitional calf exercise (mechanoreflex, metaboreflex, and central command), and electrically stimulated calf exercise (mechanoreflex and metaboreflex but no central command) at 35% of maximum voluntary contraction (n = 16). In addition, a period of postexercise muscle ischemia (PEMI) was used to isolate the metaboreflex. Blood pressure, cardiac output, and the end-tidal partial pressure of carbon dioxide (Pet(CO2)) were also measured. ACA V(mean) was unchanged from rest during either sustained or rhythmic calf muscle stretch (P > 0.05). However, ACA V(mean) was increased from rest during both isometric (+15 +/- 1%) and rhythmic (+15 +/- 2%, voluntary exercise P < 0.05) but remained unchanged during stimulated exercise (P > 0.05). Isometric and rhythmic exercise-induced increases in blood pressure and cardiac output were similar during voluntary and stimulated exercise (P > 0.05 between conditions). Blood pressure remained elevated during PEMI after all exercise conditions (P < 0.05 vs. rest), whereas cardiac output and ACA V(mean) were not different from rest (P > 0.05). Pet(CO2) was unchanged from rest throughout. These data suggest that selective activation of skeletal muscle afferents (i.e., stretch, PEMI, or stimulated exercise) does not increase ACA V(mean) and that increases in ACA V(mean) during volitional contractions of an exercising calf muscle are dependent on the presence of central command.
本研究的目的是确定来自机械性（机械反射）和代谢性（代谢反射）敏感肌肉传入神经的外周反馈以及来自高级中枢的中枢信号（中枢指令）对运动诱导的局部脑灌注增加的相对重要性。为实现这一目的，在最大自主收缩的35%强度下，对16名受试者进行了如下实验并评估大脑前动脉（ACA）平均血流速度（V(mean)）反应：持续有节奏的被动小腿肌肉拉伸（机械反射）、自主小腿运动（机械反射、代谢反射和中枢指令）以及电刺激小腿运动（机械反射和代谢反射但无中枢指令）。此外，利用运动后肌肉缺血期（PEMI）来分离代谢反射。同时测量血压、心输出量和呼气末二氧化碳分压（Pet(CO2)）。在持续或有节奏的小腿肌肉拉伸过程中，ACA V(mean)与静息时相比无变化（P>0.05）。然而，在等长运动（+15±1%）和有节奏运动（+15±2%，自主运动P<0.05）过程中，ACA V(mean)较静息时增加，但在电刺激运动过程中保持不变（P>0.05）。在自主运动和电刺激运动过程中，等长运动和有节奏运动引起的血压和心输出量增加相似（不同条件之间P>0.05）。在所有运动条件后的PEMI期间，血压均保持升高（与静息相比P<0.05），而心输出量和ACA V(mean)与静息时无差异（P>0.05）。Pet(CO2)在整个过程中与静息时无变化。这些数据表明，选择性激活骨骼肌传入神经（即拉伸、PEMI或电刺激运动）不会增加ACA V(mean)，并且在自主收缩运动的小腿肌肉过程中，ACA V(mean)的增加依赖于中枢指令的存在。
