Mixed factors affecting plantar pressures and center of pressure in obese children: Obesity and flatfoot.

<bold>Background: </bold>Flatfoot has a very high incidence of obese children. Functional parameters such as plantar pressures and center of pressure (COP) are sensitive to foot type. However, previous foot biomechanical studies of obese children rarely excluded the flatfoot as a prerequisite of the participants involved.<bold>Research Question: </bold>This study aimed to determine whether it is essential to define flatfoot as a subject screening criterion in the foot biomechanical study for obese children.<bold>Methods: </bold>Foot types were classified by arch index (AI). Totally 21 obese children with flatfoot (OF group) along with matched control groups of obese children with normal foot (ON group) and normal-weighted children with flatfoot (NF group) were selected from our database. Barefoot walking trails were conducted using Footscan® plate system. Peak force (PF), peak pressure (PP), pressure-time integral (PTI), contact area (CA) and COP data were recorded. Independent t-test and effect size were used to compare the data between the study group and the control groups. Intraclass correlation coefficient was used to measure the between-trail reliability for the dependent variables.<bold>Results: </bold>In comparison with the OF group, an upward trend for PF, PP and PTI was found for the ON group, while an opposite tendency for the NF group. The OF group displayed a significant larger CA under the midfoot region than the NF group even if there is no significant difference for AI. The OF group displayed a more medial shift of COP progression compared to the ON group. But no significant differences were found for COP parameters between the OF group and the NF group.<bold>Significance: </bold>This study provided substantial evidence to support that prospective foot biomechanical research on the obese group needs to identify the flatfoot as one of the subject screening criteria to carry out more reliable results without producing confounding effects. [ABSTRACT FROM AUTHOR]