Orizio C, Baratta R V, Zhou B H, Solomonow M, Veicsteinas A
Dipartimento di Scienze Biomediche e Biotecnologie, Cattedra di Fisologia Umana, Università degli Studi di Brescia, Italy.
J Electromyogr Kinesiol. 1999 Apr;9(2):131-40. doi: 10.1016/s1050-6411(98)00044-3.
The aim of this study was to compare the force (F) and the muscle transverse diameter changes during electrical stimulation of the motor nerve. In four cats the exposed motor nerves of the medial gastrocnemius were stimulated as follows: (a) eight separate trials at fixed firing rates (FR) from 5 to 50 Hz (9 s duration, supramaximal amplitude); (b) 5 to 50 Hz linear sweep in 2.5, 5, 7.5 and 10 s (supramaximal amplitude, separate trials); (c) four separate trials at 40 Hz, the motor units (MUs) being orderly recruited in 2.5, 5, 7.5 and 10 s. The muscle surface displacement was detected by a laser distance sensor pointed at the muscle surface. The resulting electrical signal was termed surface mechanomyogram (MMG). In stimulation patterns (a) and (b) the average F and MMG increased with FR. With respect to their values at 50 Hz the amplitude of the unfused signal oscillations at 5 Hz was much larger in MMG than in force. The signal rising phase was always earlier in MMG than in F. In (c) trials, F increased less in the first than in the second half of the recruiting time. MMG had an opposite behaviour. The results indicate that the force and the lateral displacement are not linearly related. The different behaviour of F and MMG, from low to high level of the MUs' pool activation, suggests that the force generation and the muscle dimensional change processes are influenced by different components of the muscle mechanical model.
本研究的目的是比较运动神经电刺激期间的力（F）和肌肉横径变化。在4只猫中，对腓肠肌内侧暴露的运动神经进行如下刺激：（a）以5至50Hz的固定放电频率（FR）进行8次单独试验（持续时间9s，最大刺激强度）；（b）在2.5、5、7.5和10s内进行5至50Hz的线性扫描（最大刺激强度，单独试验）；（c）在40Hz下进行4次单独试验，运动单位（MU）在2.5、5、7.5和10s内按顺序募集。用指向肌肉表面的激光距离传感器检测肌肉表面位移。所得到的电信号称为表面肌动图（MMG）。在刺激模式（a）和（b）中，平均F和MMG随FR增加。相对于其在50Hz时的值，MMG中5Hz时未融合信号振荡的幅度在力方面要大得多。MMG中的信号上升阶段总是比F中的更早。在（c）试验中，F在募集时间的前半段增加幅度小于后半段。MMG则表现相反。结果表明，力和横向位移并非线性相关。从低到高的运动单位池激活水平下，F和MMG的不同表现表明，力的产生和肌肉尺寸变化过程受肌肉力学模型不同成分的影响。
