AIM To investigate the effect of introducing an interphase interval to a biphasic pulse on force production and muscle fatigue, during stimulation of the wrist and finger extensors and to determine whether the IPI effect on force is dependent on electrode position. METHODS Electrically-induced contraction forces of the wrist and finger extensors were measured in 15 healthy subjects undergoing stimulation. These forces were assessed with interphase interval settings at 0, 100, and 200μs, with both electrodes located just distal to common extensor origin (proximal placement) or with the distal electrode placed over the extensor and abductor policies longus muscles (distal placement). The degree of discomfort related to stimulation sensation was evaluated using a numeric rating scale. Muscle fatigue was measured during proximal placement. RESULTS Under both electrode locations, introduction of 100 or 200 μs interphase interval enhanced force production; yet, only the 100μs interphase interval increased force without increasing discomfort. Additionally, stimulation sensation was more comfortable with proximal placement. Introducing interphase interval significantly increased the muscle force output during a repetitive stimulation fatigue protocol. CONCLUSIONS When using neuromuscular electrical stimulation to activate the wrist and finger extensors, clinicians should consider locating both stimulating electrodes proximally over the extensor surface of the forearm and apply a 100 µs interphase interval to a biphasic pulse. Future research that should establish these findings in individuals with various pathologies, especially in patients with residual hand spasticity.

中文翻译：

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优化手张开的神经肌肉电刺激。

目的研究在手腕和手指伸肌刺激过程中，在双相脉冲中引入相间间隔对力产生和肌肉疲劳的影响，并确定IPI对力的影响是否取决于电极位置。方法在15名接受刺激的健康受试者中，测量手腕和手指伸肌的电诱导收缩力。这些力是通过相间间隔设置为0、100和200μs来评估的，两个电极都位于共同伸肌起源的远端（近端放置），或者远端电极置于伸肌和外展肌策略的长肌上方（远端放置）。使用数字评分量表评估与刺激感觉有关的不适程度。在近端放置期间测量肌肉疲劳。结果在两个电极位置下，引入100或200μs的相间间隔可增强力的产生。然而，只有100μs的相间间隔增加了作用力，而没有增加不适感。此外，近端放置刺激感更舒适。在重复刺激疲劳方案中，引入相间间隔可显着增加肌肉力量输出。结论当使用神经肌肉电刺激激活腕部和手指伸肌时，临床医生应考虑将两个刺激电极放置在前臂伸肌表面的近端，并对双相脉冲施加100 µs的相间间隔。未来的研究应在具有各种病理学的个体中建立这些发现，尤其是在残留手部痉挛的患者中。