Center of gravity dynamic stability in normal and vestibulopathic gait.

The purpose of this study was to examine the three-dimensional whole body center of gravity (CG) kinematics during free and paced gait in healthy subjects (n=16) and individuals with vestibulopathy (n=8). The cycle time, double and single stance phase durations, values and timing of CG forward velocity, and CG vertical displacement were recorded using an 11 segment, 66 degree of freedom whole body model. The free speed gait of the vestibulopathic individuals was remarkable for increased cycle time, increased percentage of time spent in the double stance phase, decreased forward velocity of the CG, and decreased vertical displacement of the CG. However, during paced gait, no statistically significant differences were found between the vestibulopathic and control groups in all measures. In all groups, CG horizontal velocity maxima and minima significantly lagged CG vertical minima and maxima respectively. We conclude that whole body CG control does not result purely from optimization of mechanical potential and kinetic energy exchanges: our temporal offsets in the maxima and minima of the CG horizontal velocity and vertical displacement make this mechanically impossible. Furthermore, individuals with vestibular impairment may self-select a slower walking speed to ease their biomechanic stability challenge despite being able to ambulate faster with 'normal' CG velocities and displacements. Copyright 1998 Elsevier Science B.V.