Assessment of Lumbar Muscles Activation in Patients with Unilateral Myofascial Pain Syndrome Based on High-density Surface Electromyography: A Preliminary Study.

Myofascial pain syndrome (MPS) is a chronic musculoskeletal pain characterized by myofascial trigger points (MTrPs), which are related to dysfunctional motor endplate. However, the changes in neuromuscular functions incurred by the MTrPs are still not well understood. High-density surface electromyography (HD-sEMG) provides a non-invasive method to identify motor endplates and quantify the muscle activity distribution. This study aimed to analyze the differences in lumbar muscle activity distribution between patients with MPS and healthy individuals during an isometric trunk extension task and to compare the location between the centroid of the low-energy region calculated from the HD-sEMG topography and the MTrPs identified by palpation. We observed that the centroid of the low-energy region and the location of the MTrPs identified by palpation are very close to each other. Furthermore, we found that, as the fatiguing task progressed, the muscle activity distribution changed more significantly in healthy participants, compared to MPS patients. These results demonstrated the potential feasibility of using HD-sEMG as a tool for assessing the neuromuscular function of MPS.