Jerk analysis of active body-weight-transfer.

Recent studies have shown that whole-body vibration improves posture and gait control in stroke patients. Patients with degenerative cerebellar disease suffer from ataxic gait also which is characterised by the variation of gait pattern. Our interest is to test whole-body vibration as a method for rehabilitation treatment in cerebellar patients and to assess the success of the treatment using dynamic tests. The aim of this study was to introduce a method for quantifying movement dynamics during an active voluntary sidestep that results in a body-weight-transfer. Subjects had to perform a step from a feet-apart-position to a feet-together-position and back again. The algorithms presented in this study allow automatic identification of the timing of the dynamic phases by analysing the centre of pressure trajectory. For this study the time flow of averaged speed, acceleration, and jerk was calculated for the active movement only. This study demonstrates that jerk provides a sensitive measure for the improvement in gait in rehabilitation and during training.