The effect of treatment on myofascial trigger points in upper trapezius muscle, EMG fatigue parameters, joint range of motion, pain and perception of disability

Abstract

Myofascial trigger points (TP), are muscle manifestations 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 pain. 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) behavior and endurance time), head-neck range of motion, and subjective measurements such as pain levels of patients and perceived disability. In order to measure the head-neck range of motion, a new method was developed to measure this motion simultaneously in three planes. Subjects were nine patients with myofascial TPs in upper trapezius and nine healthy individuals. Patients were tested once before treatment and at three ntervals after the first treatment; the last test session occurred after treatment was completed. Healthy subjects were tested three times with a three week interval between the sessions. EMG signals were recorded simultaneously by surface electrodes from the upper trapezius and middle deltoid muscles in two different test positions until the limit of subjective fatigue. EMG results showed significant improvement after treatment; however the treated afflicted muscle still had a different fatigue pattern compared to that of normal muscles. Results also showed significant improvements in head-neck range of motion and subjective measurements in patients after treatment. Based on the EMG results from the healthy subjects, this study presents a functionally-related EMG fatigue pattern for trapezius and challenges the common interpretation of the RMS behavior with fatigue.