Evaluation of trunk stability in the sitting position using a new device.

The purpose of this study was to evaluate trunk stability in seated elderly and young individuals using a new device that inclines a seat while tracking the center of pressure (CoP). We evaluated the locus of CoP, locus length, locus length per second, enveloped area, root mean square area, and locus length per unit area (LNG/AREA). LNG/AREA, which reflects postural adjustments controlled by the spinal proprioceptive reflexes of the lower limbs, was not significantly different between young and elderly individuals. Our device measured trunk stability without influence from the lower extremities, which explains why LNG/AREA did not significantly differ between young and elderly individuals. These findings indicate that the new device can be used to quantify dynamic trunk stability.