Roujeau Thomas, Decq Philippe, Lefaucheur Jean-Pascal
Service de Physiologie-Explorations Fonctionnelles, Centre Hospitalier Universitaire Henri Mondor, 51 avenue du Marechal de Lattre de Tassigny, 94010 Creteil, France.
Clin Neurophysiol. 2004 Jun;115(6):1313-9. doi: 10.1016/j.clinph.2004.01.020.
A potent stretch reflex originates in muscle spindle secondary endings and is mediated by group II muscle afferents. Electrical stimulation of peripheral nerve could also induce group II facilitation, as found in single motor unit recordings for various nerve-muscle combinations in man. The aim of the present investigation was to use surface electromyogram (EMG) to record and to quantify heteronymous excitation of semitendinosus (ST) motoneurones by group II afferents of the tibial nerve.
This study included 20 healthy subjects. The conditioning stimulation of the tibial nerve was delivered at the popliteal fossa at two intensity levels and for two levels of ST contraction. EMG activity was recorded by surface electrodes placed over the ST muscle, and the averaged and rectified ST EMG signal was analyzed.
We observed 4 periods of interest: a first period of prestimulus background EMG activity; a second period of early reinforcement of ST EMG activity starting 30 ms poststimulus and lasting for 35-45 ms; a third period of relative inhibition of ST contraction; a fourth period of late reinforcement of poststimulus ST EMG activity.
We hypothesized that the early period of facilitation was mainly related to heteronymous excitation of ST motoneurones by group II afferents on the basis of the following observations: (i) the amount of facilitation increased for a high stimulus intensity level, which was suitable for group II recruitment; (ii) the onset latency of this facilitation was consistent with the theoretically calculated latency of a group II-mediated reflex.
Surface EMG recording offers various advantages compared to single motor unit recording to study group II facilitation in the ST muscle. This technique could be applied in the future to confirm that heteronymous reflex excitation by group II afferents is enhanced in spastics and plays an important role in the development of lower limb spasticity.
一种强大的牵张反射起源于肌梭的次级末梢，并由II类肌传入纤维介导。对周围神经进行电刺激也可诱发II类易化作用，正如在人体各种神经 - 肌肉组合的单运动单位记录中所发现的那样。本研究的目的是使用表面肌电图（EMG）来记录并量化胫神经II类传入纤维对半腱肌（ST）运动神经元的异源兴奋作用。
本研究纳入了20名健康受试者。在腘窝处对胫神经进行条件刺激，设置两个强度水平，并针对ST的两种收缩水平进行刺激。通过置于ST肌肉上方的表面电极记录EMG活动，并对平均整流后的ST EMG信号进行分析。
我们观察到4个感兴趣的时期：刺激前背景EMG活动的第一个时期；刺激后30毫秒开始并持续35 - 45毫秒的ST EMG活动早期增强的第二个时期；ST收缩相对抑制的第三个时期；刺激后ST EMG活动晚期增强的第四个时期。
基于以下观察结果，我们推测易化作用的早期主要与II类传入纤维对ST运动神经元的异源兴奋有关：（i）在适合II类纤维募集的高刺激强度水平下，易化作用的量增加；（ii）这种易化作用的起始潜伏期与理论计算的II类介导反射的潜伏期一致。
与单运动单位记录相比，表面EMG记录在研究ST肌肉的II类易化作用方面具有多种优势。该技术未来可用于证实II类传入纤维的异源反射兴奋在痉挛患者中增强，并在下肢痉挛的发展中起重要作用。
