Assessment of Upper Trapezius Muscle Fatigue in Subclinical Myofascial Pain Syndrome Participants Versus Healthy Control by JASA Method

Background: Myofascial trigger points are most commonly occurs in the upper trapezius, which is the highest sensitive muscle in the body. Joint Analysis of Electromyography (EMG) Spectrum and Amplitude (JASA) method was applied to evaluate the occurrence of muscular fatigue during consecutive gripping exertions. Methods: 64 right handed subjects took part in this study. Prior to the fatigue test, the maximal voluntary contraction was measured three times. A force gauge was used for force measurement while recording with a monitor. Measurement was initiated with a Maximum Voluntary Contraction (MVC) force of the trapezius. Results: After accomplishing fatigue protocol, they showed signs of exhaustion; however, they were not subjectively evaluated for fatigue. As the protocol aimed at assessing muscle fatigue, a force level of 80% MVC was induced. Conclusion: As revealed by the plots, the lower left quadrant could be defined as having an ‘‘force reduction’’ rather than a ‘‘fatigue’’ trait based on the natural pushing up characteristics based at the JASA plot definition, muscle fatigue or force reduction become manifested by way of above 90% of the 20 dots after fatigue test. Through the JASA method, researchers could gain insight in to the muscular fatigue condition as well as the possible underlying mechanisms.