Insertion of fine-wire electrodes does not alter EMG patterns in normal adults

Dynamic electromyography (EMG) utilizes either surface or fine-wire intramuscular electrodes to collect data on muscle activity. The question arises whether or not insertion of fine-wire electrodes alters the patterns they are intended to reflect. This study was designed to evaluate the affect of fine-wire electrode insertion on muscle activity during gait in normal adults without muscle tone abnormalities by comparing ensemble-averaged surface EMG patterns and variance ratios (VR) before and after fine-wire electrode insertion. Pearsonʹs correlation coefficients (r) and variance ratios (VR) were determined to assess the degree of similarity between pre- and post-insertion surface EMG patterns and the degree of repeatability of the muscle activity respectively. The ensemble-averaged signals reflect a high degree of pattern similarity as evidenced by high r values (usually greater than 0.90). Pre- and post-insertion VRs are similar. The low mean VRs indicate reasonable reproducibility for both pre- and post-insertion. We concluded that fine-wire electrodes had no significant affect on muscle activity during gait as measured by surface EMG signals under our conditions in normal adults.