Bimodal Distribution of Arch Indices in Seven-year-old Boys and Girls
Date Issued
2012
Date
2012
Author(s)
Chen, Yu-Chen
Abstract
Background and purpose. Although a large proportion of foot type in children is flexible flatfoot (FFF) and a matter of great concern for parents, the ‘precise’ definition of flatfoot as well as health care remain no consensus. Flatfoot is often regarded as a cause for inferior performance in sports and fitness; therefore several models of managements have been applied. This study was to investigate the association between flatfoot related parameters and physical fitness after controlling the confounding effects of age and gender.
Methods. After being proven by institutional review board, researchers collected foot prints and three tests of physical fitness, including standing long jump, 20-meter dash, and standing on one foot, from first grade students in 3 urban elementary schools. Chippaux-Smirak Index (CSI) and Staheli’s arch index (AI) were computed from foot prints and their association with physical fitness was studied using independent t test and correlation. Regression was used to identify the factors that could significantly explain physical fitness.
Results. The two flatfoot indices computed from 829 children (mean age 6.7 years, SD 0.33) were in bimodal (two-peak) distribution, and the trough value was 0.55 in CSI and 1.0 in AI. When divided by the trough value, children with flatter feet had greater body mass index (BMI) and inferior one leg balance (p<0.05). Boys had greater BMI and more flatfeet than girls, but only girls with flatfeet showed inferior performance in fitness. The correlations between physical fitness and CSI, AI, BMI are very low. Regression revealed physical fitness could only be explained in a minimal amount by BMI after control of gender (r2= 0.02~0.09).
Conclusion. The results may explain why flatfoot children presented with inferior physical fitness. However, correlation and regression are against flatfoot as a significant factor for physical fitness. By controlling age in a small range, the two flatfoot indices revealed that in child development there might exist two divergent groups of children. This characteristic is different from normal bell shaped distribution seen in other body measurements, and its physiological significance requires further longitudinal study.
Subjects
flexible flatfoot
Chippaux-Smirak Index
Staheli’s arch index
bimodal (two-peak) distribution
physical fitness
Type
thesis
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