Effect of Muscle Fatigue on the Upper Trapezius Muscle With and Without Myofascial Trigger Points in Students With Neck Pain: A Randomized Controlled Clinical Trial

Objectives: The purpose of this work was to explore cervical position sense and electromyographic (EMG) responses of cervical muscles during head repositioning movements in students with and without upper trapezius muscle trigger points. Materials and Methods: Forty-six right-handed men and women subjects without upper extremity disorders participated in this study. The maximal voluntary contraction (MVC) was measured three time before the fatigue test. A force gauge was used to measure force while recording with a monitor. Measurement was initiated with a MVC force before and after fatigue pain and head positioning were measured. When the protocol was accomplished, the subjects 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. Results: These findings support the argument that the precision of the neck position sense can be reduced by the fatigue of the neck muscle. Fatigue impaired balance in the trapezius muscles. After removing vision this resulted in an increased center of pressure excursions on a force platform. Motor control did not change significantly in this study. Conclusions: Fatigue had a more significant effect on cervical kinematics in the healthy subjects, probably due to the fact that altered neck motor control in volunteers implied that these individuals were not completely able to make up for fatigue of the neck muscle. Significant pain and head positioning changes were identified following fatigue applied to the pre-determined myofascial trigger points, but the changes were insignificant in the sham control group.