Repeatability of frequency of corrective foot pressure during balance control in children aged between 2 and 7

The frequency of corrective signal (the centre of corrective (COC) signal), which is the decomposition of COP (centre of pressure) and estimated COM (centre of mass) time series, is one of the indicators reflecting the quality of postural control during stance. Young children, in the period of intensive development, gradually improve the quality of postural control in a daily life. The purpose of this paper was to describe the time series of corrective centre of foot pressure repeatability in young children aged between 2 and 7 during body stability in natural stance position. 272 healthy children aged between 2 and 7 were divided into 6 age groups. Two AccuSway force platforms were used (one foot of the subject was on one platform, the second foot, on the other). The COP trajectories were the basis for the calculation of the frequency stability indices in frontal and sagittal planes for the left leg and right leg separately. The COC signals were collected by the method based on the Kuczyński viscoelastic model. In order to assess the repeatability, the concordance correlation coefficient (CCC) was used between the 1st and the 2nd trials, the 2nd and the 3rd trials, and the 1st and the 3rd trials. The maturation of postural control system goes rather slowly in two youngest groups which showed the poor repeatability in COC frequency between the 2nd and the 3rd years of life. From the 4th to the 7th year of life the inter-session repeatability rapidly increases in three consecutive trials. Poor difference of frequency concordance was found between the left and right lower limbs. It is concluded that the frequency of corrective foot pressure is the reliable indicator of postural control for children aged between 4 and 7, but not for younger ones.