The arch index: a measure of flat or fat feet?
BACKGROUND
Studies using footprint-based estimates of arch height have indicated that obesity results in a lowered medial longitudinal arch in children. However, the potentially confounding effect of body composition on indirect measures of arch height, such as the arch index, has not been investigated.


METHODS
This study assessed the body composition of 12 male and 12 female adults (mean age: 39.9 +/- 8.1 years, height: 1.724 +/- 0.101 m; weight: 95.1 +/- 13.7 kg, and BMI: 31.9 +/- 3.0 kg/m(2)) using bioelectrical impedance analysis to produce a two-component model of fat mass (FM) and fat-free mass (FFM). The dynamic arch index also was determined from electronic footprints captured during gait using a capacitive pressure distribution platform with a resolution of 4 sensors/cm(2).


RESULTS
While significant correlations were noted between FFM and the area of both the hindfoot (r =.75, p <.05) and forefoot (r =.72, p <. 05), the midfoot area was correlated only with FM (r =.54, p <.05). Similarly, the arch index was significantly correlated with the FM percentage (r =.67, p <.05).


CONCLUSIONS
The findings of this pilot study suggest that body composition influences arch index values in overweight and obese subjects. Consequently, body composition may be a confounding factor in interpreting footprint based estimates of arch height and, as such, these estimates would best be used with supplementary measures of body composition.
Wearing
Scott C
SC
School of Human Movement Studies, Queensland University of Technology, Brisbane, Queensland, Australia.
Hills
Andrew P
AP
Byrne
Nuala M
NM
Hennig
Ewald M
EM
McDonald
Michael
M
D000273:Adipose Tissue; D000328:Adult; D000886:Anthropometry / Q000379:methods; D001823:Body Composition; D003878:Dermatoglyphics; D005260:Female; D005413:Flatfoot / Q000473:pathology*; D005528:Foot / Q000473:pathology*; D006801:Humans; D008297:Male; D009765:Obesity / Q000473:pathology*; D010865:Pilot Projects; D011312:Pressure; D015203:Reproducibility of Results