Techniques to Manage ECG Artifacts When Working With Surface EMG
Surface electromyographic (SEMG) amplitude signals can often contain rhythmic spikes due to cardiogenic electrical activity. The author discusses the impact of this activity on SEMG biofeedback training and techniques to reduce the problems caused by cardiogenic electrical activity. In particular, changing the low frequency cutoff of the digital filter settings to reduce cardiogenic electrical activity is recommended as a procedure to improve the fidelity of SEMG amplitude signals.
This screen displays the filtered output, the power spectra, amplitude line graphs, and numerical (amplitude) objects for an EMG signal filtered at 20–500, 50–500, and 100–500 Hz. The recording is from the left wrist extensors and shows no ECG contribution.
Similar to Figure 1 but with placements showing significant ECG artifacts. One active electrode was placed midway between the left acromion and the C7 vertebra, and the other active electrode was placed just above the left eyebrow in the midline of the eye.
Line graphs of EMG amplitudes with different filter settings and significant ECG artifacts. Same placements as in Figure 2.
Line graphs at three different filter settings of EMG amplitude from the left anterior tibialis muscle during sustained ankle dorsiflexion. This is a site in which ECG artifacts are not typically seen and shows the dramatic impact of raising the low band pass cutoff on overall amplitude levels.
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