Fast Computational Analysis of Sway Area Using Center of Pressure Data in Normal Children and Children with Cerebral Palsy

Abstract

In this paper, we have developed an efficient method for real time computation of Center of Pressure (CoP) sway area using a fast search and sort based on a numerical approximation of the Green-Gauss method. In addition, we investigated the correlations among the velocity, acceleration, path length, sway area, and mean frequency of CoP signals during quiet standing in healthy children and in children with cerebral palsy. The Pearson correlation technique described the direction and strength of linear relationships among the CoP velocity, acceleration, and the standard metrics, such as CoP Root Mean Squared (RMS), CoP range, path length (PL), normalized path length (NPL), sway area (SA), normalized sway area (NSA), and mean frequency, respectively. Subjects were tested during eyes open and eyes closed trials to explore the significance of the visual input. Both RMS of CoP velocity and acceleration described strong correlations with NPL and NSA in the eye open test (r ≥ 0.728) and in the eye closed test (r ≥ 0.919) of normal children. Similar results were also observed in children with cerebral palsy in both eye tests. The correlation between the CoP velocity and NPL indicated that the CoP velocity metric can be considered as an indicator of NPL. Thus, the CoP velocity and CoP acceleration might be very useful as valid metrics because the real time feedback from online measurements in balance control assessment is often necessary. The described fast computation of the sway area by using CoP velocity and CoP acceleration provided valid metrics for CoP correlation analysis.