Electromyographic Activity Pattern of the Trunk Muscles

Abstract

The innervations of trunk muscles differ from those of the upper and lower extremity muscles, and they are responsible for coordinated motor control function. Local muscles, located deep in the trunk, such as transversus abdominis and multifidus, are important for coordinating motor control. Muscle activity patterns are divided into the following 3 types: 1) early activity (feedforward activity); 2) tonic activity (sustained low activity); and 3) phasic activity (explosive activity). The local muscles mainly exhibit early activity and tonic activity during limb movement and serve as the basis for various movements. In contrast, pain causes dysfunction of the local muscles. Subsequently, dysfunction of the local muscles results in compensatory hyperactivation of the superficial muscles (global muscles) and increased facet and intervertebral joint stress. Therefore, it is important to perform optimal motor control exercises for local muscles from the acute phase. For athletes, gradual exercise therapy in advance to acquire optimal local muscle function to exert greater torque is important for preventing low back pain.