Edamura M, Yang J F, Stein R B
Division of Neuroscience, University of Alberta, Edmonton, Canada.
J Neurosci. 1991 Feb;11(2):420-7. doi: 10.1523/JNEUROSCI.11-02-00420.1991.
The soleus H-reflex amplitude is deeply modulated during locomotion in humans (Capaday and Stein, 1986). Moreover, at a constant stimulus intensity, the slope of the relationship between the amplitude of the soleus H-reflex and the background electromyogram (EMG) changes with different locomotor tasks (Capaday and Stein, 1987a). Two further aspects are studied here. First, we recorded the reflex during overlapping speeds of walking (2.0-7.5 km/hr) and running (5-9 km/hr) to determine whether the speed, the motor output, or the form of locomotion was most important in setting the slope of this relationship between H-reflex and background EMG. Second, we determined the time course of change in the H-reflex amplitude and the possible site of action for the reflex depression during the transition from standing to walking. The primary determinant of the slope was found to be the form of locomotion. The differences between running and walking could not be explained entirely by either movement speed or motor output. For walking, the slope varied inversely with the speed and the motor output of locomotion. This compensation in slope as a function of motor output may prevent saturation of the motoneuron pool. The appropriate reflex amplitudes for a particular locomotor pattern are activated rapidly and completely within a reaction time, and simultaneously with the activation of muscle activity for the initiation of walking. Mechanisms for the rapid change seen during the initiation of locomotion most likely act presynaptically on the muscle spindle afferents. The time course and magnitude of this change are correlated with the activity of the tibialis anterior muscle.
在人类行走过程中，比目鱼肌H反射的波幅受到深度调制（卡帕迪和斯坦，1986年）。此外，在恒定刺激强度下，比目鱼肌H反射波幅与背景肌电图（EMG）之间关系的斜率会随不同的运动任务而变化（卡帕迪和斯坦，1987a）。本文研究另外两个方面。第一，我们在步行（2.0 - 7.5千米/小时）和跑步（5 - 9千米/小时）的重叠速度期间记录反射，以确定速度、运动输出或运动形式在设定H反射与背景EMG之间这种关系的斜率时哪个最为重要。第二，我们确定了从站立到行走过渡期间H反射波幅变化的时间进程以及反射抑制的可能作用部位。结果发现，斜率的主要决定因素是运动形式。跑步和步行之间的差异不能完全由运动速度或运动输出解释。对于步行，斜率与运动速度和运动输出成反比变化。这种作为运动输出函数的斜率补偿可能会防止运动神经元池饱和。特定运动模式的适当反射波幅会在反应时间内迅速且完全地被激活，并且与启动步行的肌肉活动激活同时发生。在运动启动期间看到的快速变化机制很可能在突触前作用于肌梭传入纤维。这种变化的时间进程和幅度与胫骨前肌的活动相关。
