Myofascial pain syndrome. Electromyographic changes associated with local twitch response

Electromyographic (EMG) recordings of the local twitch response in sixteen subjects with pain from active myofascial trigger points in the upper trapezius muscle were examined and compared with recordings from the contralateral normal muscle bands in the same individual. Needle electromyography and a specific reproducible snapping palpation technique were used to elicit and record the local twitch response. The mean value for the EMG recordings of bands with trigger points versus the normal muscle bands using the visual scoring method were 3.81 and .81 respectively. Mean values for the EMG recordings of muscle bands with trigger points versus the normal muscle using the spike counting method were 31.81 and 8.75 respectively. Both results were statistically compared using student's t-test. The motorunit electrical activity of the bands with trigger points was found to be significantly higher (p ≤ 0.001) than that of the normal muscle.