Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada.
J Electromyogr Kinesiol. 2013 Oct;23(5):1044-51. doi: 10.1016/j.jelekin.2013.07.011. Epub 2013 Aug 9.
Electromyograms (EMGs) are measured by bipolar surface electrodes that quantify potential differences. Bipolar potentials over penniform muscles may be associated with errors. Our assumption was that muscle activity can be quantified more reliably and with a higher spatial resolution using current measurements. The purpose of this work is: (a) to introduce the concept of current measurements to detect muscle activity, (b) to show the coherences observed over a segment of a typical penniform muscle, the gastrocnemius medialis where one would expect a synchronicity of the activation, and (c) to show the amount of mixing that is caused by the finite inter electrode resistance. A current amplifier was developed. EMGs were recorded at 40% of maximum voluntary contraction during isometric contractions of the gastrocnemius medialis. EMGs of twelve persons were recorded with an array of four peripheral and one central electrode. Monopolar EMGs were recorded for "all-potential", "center at current" and "all-current" conditions. Coherence revealed the similarity of signals recorded from neighboring electrodes. Coherence was high for the "all-potential", significant for the "current at center" condition and disappeared in the "all-current" condition. It was concluded that EMG array recordings strongly depends on the measurement configuration. The proposed current amplifier significantly improves spatial resolution of EMG array recordings because the inter-electrode cross talk is reduced.
肌电图（EMG）通过测量量化电位差的双极表面电极进行测量。在 penniform 肌肉上的双极电位可能与误差有关。我们的假设是，使用电流测量可以更可靠地量化肌肉活动，并且具有更高的空间分辨率。这项工作的目的是：（a）引入电流测量的概念以检测肌肉活动，（b）显示在典型 penniform 肌肉的一段上观察到的相干性，即人们预期激活同步性的比目鱼肌内侧，以及（c）显示由有限的电极间电阻引起的混合量。开发了一个电流放大器。在比目鱼肌等长收缩期间，以最大随意收缩的 40%记录 EMG。用四个外围和一个中央电极的阵列记录了 12 个人的 EMG。记录了单极 EMG 的“全电位”、“电流中心”和“全电流”条件。相干性揭示了记录自相邻电极的信号的相似性。对于“全电位”，相干性很高，对于“电流中心”条件，相干性显著，并且在“全电流”条件下消失。结论是，肌电图阵列记录强烈依赖于测量配置。所提出的电流放大器由于减少了电极间串扰，因此显著提高了肌电图阵列记录的空间分辨率。
