The effect of treatment for myofascial trigger points on the EMG fatigue parameters of shoulder muscles

Myofascial trigger points (TP), are manifestation of a regional pain disorder and are very common, particularly in trapezius. In severe cases myofascial TPs can cause disability. However, early recognition and treatment may prevent progression to chronic pains. This study investigated the effect of treatment on myofascial TPs using objective measurements such as EMG fatigue parameters (fatigue rate, RMS and mean power frequency (MPF) behaviors plus endurance time) and subjective measurements such as pain levels of patients and the perceived disability. Subjects were 9 patients with myofascial TPs in upper trapezius and 9 healthy subjects. The patients were tested once before treatment and 3 intervals after the first treatment; the last test session occurred when treatment was completed. EMG signals were recorded simultaneously by surface electrodes from the upper trapezius and middle deltoid muscles in two different test positions until the subjective fatigue limit. Results showed significant improvement after treatment; however the treated afflicted muscle still had a different fatigue pattern compared to that of normal muscles