Tal'nov A N, Cherkassky V L, Kostyukov A I
Department of Movement Physiology, A. A. Bogomolets Institute of Physiology, National Academy of Sciences, Kiev, Ukraine.
Neuroscience. 1997 Aug;79(3):923-33. doi: 10.1016/s0306-4522(96)00702-6.
The electromyograms were recorded in healthy human subjects by surface electrodes from the mm. biceps brachii (caput longum et. brevis), brachioradialis, and triceps brachii (caput longum) during slow transition movements in elbow joint against a weak extending torque. The test movements (flexion transitions between two steady-states) were fulfilled under visual control through combining on a monitor screen a signal from a joint angle sensor with a corresponding command generated by a computer. Movement velocities ranged between 5 and 80 degrees/s, subjects were asked to move forearm without activation of elbow extensors. Surface electromyograms were full-wave rectified, filtered and averaged within sets of 10 identical tests. Amplitudes of dynamic and steady-state components of the electromyograms were determined in dependence on a final value of joint angle, slow and fast movements were compared. An exponential-like increase of dynamic component was observed in electromyograms recorded from m. biceps brachii, the component had been increased with movement velocity and with load increment. In many experiments a statistically significant decrease of static component could be noticed within middle range of joint angles (40-60 degrees) followed by a well expressed increment for larger movements. This pattern of the static component in electromyograms could vary in different experiments even in the same subjects. A steady discharge in m. brachioradialis at ramp phase has usually been recorded only under a notable load. Variable and quite often unpredictable character of the static components of the electromyograms recorded from elbow flexors in the transition movements makes it difficult to use the equilibrium point hypothesis to describe the central processes of movement. It has been assumed that during active muscle shortening the dynamic components in arriving efferent activity should play a predominant role. A simple scheme could be proposed for transition to a steady-state after shortening. Decrease of the efferent inflow can evoke internal lengthening of the contractile elements in muscle and, as a result, hysteresis increase in the muscle contraction efficiency. Effectiveness in maintenance of the steady position seems to also be enhanced due to muscle thixotropy and friction processes in the joint. Hysteresis after-effects in elbow flexors were demonstrated as a difference in steady-state levels of electromyograms with oppositely directed approaches to the same joint position.
通过表面电极在健康人体受试者的肱二头肌（长头和短头）、肱桡肌和肱三头肌（长头）上记录肌电图，记录过程是在肘关节缓慢过渡运动期间，对抗微弱的伸展扭矩。测试运动（两个稳定状态之间的屈曲过渡）是在视觉控制下完成的，通过在监视器屏幕上组合来自关节角度传感器的信号和计算机生成的相应指令。运动速度在5至80度/秒之间，要求受试者在前臂运动时不激活肘伸肌。表面肌电图进行全波整流、滤波，并在10组相同测试中进行平均。根据关节角度的最终值确定肌电图动态和稳态成分的幅度，比较慢速和快速运动。在肱二头肌记录的肌电图中观察到动态成分呈指数样增加，该成分随运动速度和负荷增加而增加。在许多实验中，在关节角度的中间范围（40 - 60度）内可注意到静态成分有统计学上的显著下降，随后在较大运动时出现明显增加。即使在同一受试者的不同实验中，肌电图中这种静态成分的模式也可能不同。通常仅在显著负荷下才会记录到肱桡肌在斜坡阶段的稳定放电。在过渡运动中，从肘屈肌记录的肌电图静态成分具有可变且常常不可预测的特征，这使得难以使用平衡点假说来描述运动的中枢过程。据推测，在主动肌肉缩短过程中，传入传出活动中的动态成分应起主要作用。可以提出一个简单的方案来描述缩短后向稳态的转变。传出流入的减少可引起肌肉收缩元件的内部延长，结果是肌肉收缩效率的滞后增加。由于肌肉触变性和关节中的摩擦过程，维持稳定位置的有效性似乎也得到了增强。肘屈肌中的滞后后效应表现为在相同关节位置以相反方向接近时肌电图稳态水平的差异。
