Biomechanical and Technical Aids Unit, National Hospital for Paraplegia, SESCAM, Toledo, Spain.
Toledo Physiotherapy Research Group (GIFTO), Faculty of Physiotherapy and Nursing, Castilla La Mancha University, Toledo, Spain.
Eur J Neurosci. 2021 Oct;54(7):6575-6586. doi: 10.1111/ejn.15448. Epub 2021 Sep 27.
The posterior root muscle response (PRM) is a monosynaptic reflex that is evoked by single pulse transcutaneous spinal cord stimulation (tSCS). The main aim of this work was to analyse how body weight loading influences PRM reflex threshold measured from several lower limb muscles in healthy participants. PRM reflex responses were evoked with 1-ms rectangular monophasic pulses applied at an interval of 6 s via a self-adhesive electrode (9 × 5 cm) at the T11-T12 vertebral level. Surface electromyographic activity of lower limb muscles was recorded during four different conditions, one in decubitus supine (DS) and the other three involving standing at 100%, 50%, and 0% body weight loading (BW). PRM threshold intensity, peak-to-peak amplitude, and latency for each muscle were analysed in different conditions study. PRM reflex threshold increased with body weight unloading compared with DS, and the largest change was observed between DS and 0% BW for the proximal muscles and between DS and 50% BW for distal muscles. Peak-to-peak amplitude analysis showed only a significant mean decrease of 34.6% (SD 10.4, p = 0.028) in TA and 53.6% (SD 15.1, p = 0.019) in GM muscles between DS and 50% BW. No significant differences were observed for PRM latency. This study has shown that sensorimotor networks can be activated with tSCS in various conditions of body weight unloading. Higher stimulus intensities are necessary to evoke reflex response during standing at 50% body weight loading. These results have practical implications for gait rehabilitation training programmes that include body weight support.
后根肌反应（PRM）是一种单突触反射，可通过单次经皮脊髓电刺激（tSCS）诱发。这项工作的主要目的是分析体重负荷如何影响健康参与者从几个下肢肌肉测量的 PRM 反射阈值。PRM 反射反应通过在 T11-T12 椎骨水平以 6 秒的间隔施加 1 毫秒矩形单相脉冲，使用自粘电极（9×5cm）诱发。在四种不同条件下记录下肢肌肉的表面肌电图活动，一种是仰卧位（DS），另外三种分别涉及 100%、50%和 0%体重负荷（BW）的站立。分析了不同条件下 PRM 阈值强度、峰峰值幅度和潜伏期。与 DS 相比，PRM 反射阈值随体重卸载而增加，近端肌肉在 DS 和 0% BW 之间以及远端肌肉在 DS 和 50% BW 之间观察到最大变化。峰峰值幅度分析仅显示在 TA 中平均下降 34.6%（SD 10.4，p=0.028）和 GM 肌肉中下降 53.6%（SD 15.1，p=0.019）有统计学意义。PRM 潜伏期无显著差异。这项研究表明，在各种体重卸载条件下，tSCS 可以激活感觉运动网络。在 50%体重负荷站立时，需要更高的刺激强度来诱发反射反应。这些结果对包括体重支撑的步态康复训练计划具有实际意义。
