Neilson P D, Neilson M D
Brain Res. 1978 Mar 10;142(3):439-53. doi: 10.1016/0006-8993(78)90907-1.
Reflex responses measured during voluntary contraction of the muscle being stretched are known to differ markedly from reflex responses elicited from passive muscle. The term 'action tonic stretch reflex' or 'action TSR' has been used previously to describe a reflex response to continuous stretch, separated from voluntary activity by means of a cross-correlational and spectrographic analysis. In this paper it is proposed that the action TSR play a functional role during voluntary movement by damping the transient oscillations associated with the natural resonant frequencies of the limbs. It is suggested that oscillations excite an action TSR force response with phase lead ahead of muscle stretch. This force response can be resolved into two force components, one of which has a 90 degree phase lead ahead of muscle stretch and behaves like a viscous friction reaction force causing damping of oscillations. Three experiments which support this proposition are described. (1) Analog computer model stimulation studies of a muscle supporting a mass-spring load reveal that damping only occurs when the force response has a phase lead ahead of muscle stretch. When the force response has a phage lag behind muscle stretch, the system is unstable and the amplitude of oscillation increases with time. (2) It is demonstrated that when a mass-spring load is supported as rigidly as possible by the human arm, reaction forces from the arm damp and mass-spring oscillations more rapidly than when the mass-spring is rigidly supported. Electromyogram (EMG) recordings reveal that mass-spring oscillations excite action TSR responses with phase lead ahead of muscle stretch. (3) Recordings of elbow angle and biceps EMG during rapid forearm flexion or extension movements followed by sudden stops reveal critically damped oscillations in the elbow angle signal (i.e. no more than one or two small overshoots), which are accompanied by EMG action TSR responses with phase lead ahead of muscle stretch.
已知在被拉伸肌肉的自主收缩过程中测量到的反射反应与被动肌肉引发的反射反应有显著差异。术语“动作性强直伸展反射”或“动作性TSR”此前已被用于描述对持续伸展的反射反应，通过互相关分析和频谱分析将其与自主活动区分开来。本文提出，动作性TSR在自主运动过程中通过抑制与肢体自然共振频率相关的瞬态振荡发挥功能作用。有人认为，振荡会激发动作性TSR力反应，其相位领先于肌肉伸展。这种力反应可分解为两个力分量，其中一个在肌肉伸展之前有90度的相位领先，其行为类似于粘性摩擦反作用力，导致振荡的阻尼。文中描述了支持这一观点的三个实验。（1）对支撑质量-弹簧负载的肌肉进行模拟计算机模型刺激研究表明，只有当力反应的相位领先于肌肉伸展时才会出现阻尼。当力反应的相位滞后于肌肉伸展时，系统不稳定，振荡幅度随时间增加。（2）结果表明，当质量-弹簧负载由人手臂尽可能刚性地支撑时，手臂的反作用力比质量-弹簧被刚性支撑时更迅速地抑制质量-弹簧振荡。肌电图（EMG）记录显示，质量-弹簧振荡会激发动作性TSR反应，其相位领先于肌肉伸展。（3）在快速前臂屈伸运动后突然停止时记录肘部角度和肱二头肌EMG，结果显示肘部角度信号出现临界阻尼振荡（即不超过一两个小的过冲），同时伴有相位领先于肌肉伸展的EMG动作性TSR反应。
