Relationship between spinal range of motion and trunk muscle activity during trunk rotation.

Abstract

[Purpose] The aim of this study was to clarify the relationship between spinal range of motion and trunk muscle activity during trunk rotation using a three-dimensional motion analysis system and surface electromyography. [Subjects and Methods] The subjects comprised 11 healthy men. A three-dimensional motion analysis system measured the trunk rotational angle of 4 segments of the thoracic vertebrae and 2 segments of the lumbar vertebrae. Surface electromyography measured the activities of the unilateral latissimus dorsi, lumbar multifidus, rectus abdominis, external oblique, internal oblique, and transversus abdominis muscles. [Results] During ipsilateral rotation at thoracic vertebral levels, the muscle activity of the latissimus dorsi and external oblique was significantly increased compared with the activity in the 0–10% range of trunk rotation. During early ipsilateral rotation at lumbar vertebral levels, the muscle activity of the internal oblique and transversus abdominis was significantly increased compared with that in the 0–10% range of trunk rotation. During contralateral rotation at both thoracic and lumbar vertebral levels, the muscle activity of the external oblique was significantly increased compared with that in the 0–10% range of trunk rotation. [Conclusion] This study indicates that it is important to consider vertebral segments and spinal range of motion during trunk rotation.