Are human anticipatory postural adjustments affected by a modification of the initial position of the center of gravity?

During a lateral leg raising task, the position of the center of gravity (CG) in the horizontal plane shifts towards the supporting leg prior to the movement onset. The aim of this study was to explore whether the anticipatory postural adjustments were calibrated as a function of the initial horizontal location of the CG. Experiments were performed on 8 healthy subjects, with three initial positions of the CG (close to the supporting leg, between the two legs, close to the moving leg). Simultaneous kinematic, kinetic and electromyographic (EMG) data were recorded with the ELITE. system. The results show that the duration of the kinetic variables and EMG pattern are scaled as a function of the distance covered by the CG and constitute the means of modulating the CG shift. They suggest that the evaluation of the support conditions is necessary to calibrate the CG shift, this is done during the early phase of the postural adjustments.