Spinal load changes during rotatory dynamic sitting

Objective. To measure load and moment changes acting on the lumbar spine during rotatory sitting. Background. A new chair concept generating dynamic stimuli by alternating rotations in the horizontal plane of the chair's seat was recently developed. Methods. Load and moment changes were measured telemetrically with a spinal fixator device in vivo. Results. A rotatory frequency of 0.22 Hz with an amplitude of 1.8 degrees to the right and left side showed maximum axial force changes in the fixator of 23 N and maximum bending moment changes of 0.52 Nm. Conclusions. Lumbar force and moment changes during dynamic sitting occur, although only one patient was included in the study. Reasons could be temporary muscular activation in order to adapt the body's equilibrium conditions at the end-point rotation.