Kinematic analysis of thoracolumbar movement during trunk extension in healthy males

Abstract

The purpose of this study was to investigate the kinematic characteristics of the thoracolumbar area during trunk extension.

Trunk extension movement was carried out in a standing position under two different conditions by subjects as an experimental task. The first condition was trunk extension from a standing position (free, unfixed condition),and the second was trunk extension with the lower limbs fixed and leaning on a special stable stand, to minimize trunk muscle activity in the maximum extension position (fixed condition). Trunk muscle activity and extension angle from standing to the maximally extended position was measured during the experimental task. The exten sion angle was measured by dividing the thoracolumbar area into six segments, using three-dimensional motion analysis systems.

In the fixed condition, muscle activity of the rectus abdominis muscle was significantly less than that under free,unfixed conditions, and the extension angle was greater in all but the middle-upper and upper-thoracic segments than under the free, unfixed conditions. Under the free, unfixed conditions, the extension angle of the lower lumbar segment was the greatest and the movement of the upper-lumbar segment was greater than that of all other thoracic segments.