SURFACE AND WIRE EMG CROSSTALK IN NEIGHBORING MUSCLES

Surface and wire myoelectric activity of the medial gastrocnemius (MG), lateral gastrocnemius (LG) and tibialis anterior (TA) of the cat were recorded during supramaximal stimulation applied via their nerves before and after the muscle nerve to the LG and TA were cut in order to determine the amount of EMG crosstalk amongst neighbouring muscles. It was shown that the peak-to-peak (p-p) amplitude and mean absolute value (MAV) of crosstalk M waves recorded from the LG and TA after their nerve was cut did not exceed 5% of their maximal value for surface electrodes and 2.5% of their maximal value for wire electrodes. EMG crosstalk values were similar in terms of peak to peak and MAV. Surface EMG crosstalk values were significantly higher in preparations in which a substantial amount of subcutaneous fat covered the muscles, being 20 (+/- 16.6) % MAV and 16 (+/- 12) % p-p. During increasing force contraction (accomplished by orderly recruitment of motor units) from 10-100% of the maximal force of the MG the corresponding crosstalk in the LG and TA increased linearly with the EMG of the MG. It is concluded that the crosstalk problem in surface recording is negligible for most biomechanical studies in which standard EMG recording protocol is employed, yet a warning is issued against the indiscriminate recording of surface EMG from muscles covered by adipose tissue.