Background Endogenous paired associative stimulation (ePAS) is a neuromodulatory intervention that has potential to aid stroke recovery. ePAS involves pairing endogenous electroencephalography (EEG) signals known as movement-related cortical potentials (MRCPs), with peripheral electrical stimulation. Previous studies have used transcranial magnetic stimulation (TMS) to demonstrate changes in corticomotor excitability following ePAS. However, the use of TMS as a measure in stroke research is limited by safety precautions, intolerance, and difficulty generating a measurable response in more severely affected individuals. We were interested in evaluating the effect of ePAS using more feasible measures in people with stroke. This study asks whether ePAS produces immediate improvements in the primary outcomes of maximal voluntary isometric contraction (MVIC) and total neuromuscular fatigue of the dorsiflexor muscles, and in the secondary outcomes of muscle power, voluntary activation (VA), central fatigue, peripheral fatigue, and electromyography activity. Method In this repeated-measures cross-over study, 15 participants with chronic stroke completed two interventions, ePAS and sham, in a randomized order. During ePAS, 50 repetitions of visually cued dorsiflexion were completed, while single pulses of electrical stimulation were delivered to the deep branch of the common peroneal nerve. Each somatosensory volley was timed to arrive in the primary motor cortex at the peak negativity of the MRCP. Univariate and multivariate linear mixed models were used to analyze the primary and secondary data, respectively. Results There was a statistically significant increase in dorsiflexor MVIC immediately following the ePAS intervention (mean increase 7 N), compared to the sham intervention (mean change 0 N) (univariate between-condition analysis p = 0.047). The multivariate analysis revealed a statistically significant effect of ePAS on VA of the tibialis anterior muscle, such that ePAS increased VA by 7 percentage units (95% confidence interval 1.3–12.7%). There was no statistically significant effect on total neuromuscular fatigue, muscle power, or other secondary measures. Conclusion A single session of ePAS can significantly increase isometric muscle strength and VA in people with chronic stroke. The findings confirm that ePAS has a central neuromodulatory mechanism and support further exploration of its potential as an adjunct to stroke rehabilitation. In addition, the findings offer alternative, feasible outcome measures for future research. Clinical trial registration Australia New Zealand Clinical Trials Registry ACTRN12617000838314 (www.anzctr.org.au), Universal Trial Number U111111953714.

中文翻译：

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与运动相关的皮层电位配对的外周电刺激可改善中风后的等长肌肉力量和自主激活

背景 内源性配对联想刺激 (ePAS) 是一种神经调节干预，有可能帮助中风恢复。ePAS 涉及将称为运动相关皮层电位 (MRCP) 的内源性脑电图 (EEG) 信号与外周电刺激配对。以前的研究使用经颅磁刺激 (TMS) 来证明 ePAS 后皮质运动兴奋性的变化。然而，在中风研究中使用 TMS 作为一项措施受到安全预防措施、不耐受以及难以在受影响更严重的个体中产生可测量反应的限制。我们有兴趣使用更可行的措施评估 ePAS 对卒中患者的影响。本研究询问 ePAS 是否能立即改善最大自主等长收缩 (MVIC) 和背屈肌总神经肌肉疲劳的主要结果，以及肌肉力量、自主激活 (VA)、中枢疲劳、外周疲劳、和肌电图活动。方法 在这项重复测量交叉研究中，15 名慢性中风参与者以随机顺序完成了两种干预措施，即 ePAS 和假手术。在 ePAS 期间，完成了 50 次重复的视觉提示背屈，同时将单脉冲电刺激传递到腓总神经的深支。每个体感截击都被定时到达初级运动皮层，达到 MRCP 的负峰值。单变量和多变量线性混合模型分别用于分析主要和次要数据。结果 与假干预（平均变化 0 N）相比，在 ePAS 干预（平均增加 7 N）后，背屈肌 MVIC 立即显着增加（单变量条件间分析 p = 0.047）。多变量分析揭示了 ePAS 对胫骨前肌 VA 的显着影响，例如 ePAS 使 VA 增加了 7 个百分比单位（95% 置信区间 1.3-12.7%）。对总神经肌肉疲劳、肌肉力量或其他次要指标没有统计学上的显着影响。结论 单次 ePAS 可以显着增加慢性中风患者的等长肌肉力量和 VA。研究结果证实 ePAS 具有中枢神经调节机制，并支持进一步探索其作为中风康复辅助手段的潜力。此外，研究结果为未来的研究提供了替代的、可行的结果措施。临床试验注册澳大利亚新西兰临床试验注册 ACTRN12617000838314 (www.anzctr.org.au)，通用试验号 U111111953714。