Computerized assessment of voluntary control in the shift of the center of pressure: a pilot study

The aim of the study was to test a new stabilometric platform (BioGP) designed to provide visual feedback to patients with balance disorders performing sustained voluntary shifts of their center of pressure (COP). Twenty-five outpatients with mild to moderate impairments of balance due to multiple sclerosis (MS) and 23 healthy subjects volunteered for the study. Patients' control of balance in static conditions was first rated on the Ataxia Battery and the Motricity Index; all subjects were then asked to stand on the platform in front of a large screen and try to move a visual target representing the momentary position of their COP along two vertical paths and one horizontal paths by appropriate movements of their hips and ankles along the lateral and antero-posterior planes. To assess the validity of BioGP, clinical scores of static balance were correlated with measures of speed and accuracy on the platform tasks. To assess the sensitivity of the equipment to poor balance control, patients' measures were compared with those of healthy subjects. Pearson's correlation coefficients between the Ataxia Battery scores and BioGP data ranged between -0.4 and - 0.82. As a group, patients performed statistically worse than controls on most BioGP measures. The graphic output of BioGP also contributed to define the dynamic relations between momentary COP position and balance control. These preliminary findings suggest a possible use of the system as both an evaluation and rehabilitation instrument.