EVALUATION OF METHODS TO MINIMIZE CROSS-TALK IN SURFACE ELECTROMYOGRAPHY

The purposes of this study were to quantify the effectiveness of vario us methods to minimize cross talk in surface electromyography (EMG) us ing common recording equipment, and to compare the intra- and interday variabilities of signals recorded with these methods. Comparisons wer e made for signals recorded with the single differential (SD), double differential (DD) and branched electrode (BE) techniques with large an d small electrodes and corresponding interelectrode distances. The amo unt of cross talk in tibialis anterior EMG signals during maximum volu ntary effort (MVE) triceps surae excitation was estimated using a prot ocol involving electrical stimulation of the triceps surae via the tib ial nerve. In SD signals, cross talk averaged 12.2 and 10.2 percent MV E, for the large and small interelectrode distances, respectively. DD and BE signals contained significantly less cross talk (approximately 5 percent MVE for both techniques and interelectrode distances) than S D signals. The intra- and interday variabilities associated with these methods were estimated by recording tibialis anterior EMG signals dur ing maximum voluntary isometric dorsiflexion (3 trials on each of 2 da ys) and calculating coefficients of variation for average-rectified va lues and median frequencies. EMG signals recorded with the small inter electrode distance showed greater interday amplitude variability than those recorded with the large interelectrode distance. Intra- and inte rday amplitude variabilities were similar across SD, DD and BE recordi ng techniques. Intra- and interday frequency variabilities were simila r across all experimental conditions. Thus, the DD and BE techniques, in conjunction with the large interelectrode distance (and large elect rodes), provide a signal which contains significantly less cross talk than the SD technique without sacrificing intra- and interday amplitud e and frequency stability.