Exploration of Axis for Dynamic Measurement of Trunk Extension Torque

Abstract

We simulatively prepared voluntary movements based on the movements of isokinetic measurement of trunk extension torque in order to esitimate the axis of the movement. By Kin-Com 500H, 25 healthy female subjects performed voluntary movements at trunk flexion of 40 degrees and extension of 20 degrees. The difference between the 4th spine of thoracic vertebrae and a measurement arm was recorded, and the axis of the movement was obtained from the equation, assuming that the movement is a circular motion. From the results, the mean X axis was supposed 1-2 cm posterior to the middle point between anterior and posterior superior iliac spines, ranged longitudinally from 2 to 5 cm. The mean Y axis was considered 2-5 cm lower than the middle point between anterior and posterior superior iliac spines with a vertical range of 2 to 9 cm. There were considerably big differences in the axis among the subjects.