Comparison of electromyographic signals from monopolar current and potential amplifiers derived from a penniform muscle, the gastrocnemius medialis

Wearable Current-Based ECG Monitoring System with Non-Insulated Electrodes for Underwater Application

“…Our previous current-based concept [18,19] was implemented and extended. Originally intended for the measurement of muscle activity in electromyograms, we showed that the concept works equally well for the measurement of the electrocardiogram in underwater conditions.…”

Monopolar electromyographic signals recorded by a current amplifier in air and under water without insulation

“…Signals were derived from electrical current using the monopolar current amplifier (also called a trans-impedance amplifier) with a feedback resistor of 2200 kX and a built-in band pass filter (10-500 Hz) as described previously (von Tscharner et al, 2013). The second stage amplification was set to 1, thereby resulting in a measured voltage of the EMG-signal of 2200 kX times the current entering the electrode.…”

“…Despite limitations with respect to penniform muscles (Dimitrova et al, 1999;Mesin et al, 2011;von Tscharner et al, 2013), bipolar electrodes are used extensively due to their apparent advantage of reducing noise by sampling the potential difference across the electrodes (Cram et al, 1998). Another major limitation of bipolar electrodes is the fact that skin resistance is not large enough to prevent some lateral current flow across the skin between the electrodes (von Tscharner et al, 2013). The presence of sweat and water on or around the skin and electrodes, therefore, will only exacerbate this 'short-circuit' effect, making the detection of muscle activity difficult or impossible.…”

“…Nonetheless, in normal dry conditions a surface potential builds up. Rather than allowing these charges to build on the surface, it is possible to remove them by measuring them as currents (von Tscharner et al, 2013). As shown in von Tscharner et al (2013), currents reflect the muscle activity equally well as the potentials created at the surface of the skin.…”

“…It was recently proposed and demonstrated that one can use current (or trans-impedance) amplifiers with a monopolar electrode setup, instead of potential amplifiers, to record EMG-currents (von Tscharner et al, 2013). A current amplifier captures or injects the charges in such a way that the potential under the electrode remains at the potential of the ground electrode.…”