Does obesity influence foot structure and plantar pressure patterns in prepubescent children?

OBJECTIVE: This study examined the effects of obesity on plantar pressure distributions in prepubescent children. DESIGN: Field-based, experimental data on BMI (body mass index), foot structure and plantar pressures were collected for 13 consenting obese children and 13 non-obese controls. SUBJECTS: Thirteen obese (age 8.1 +/- 1.2 y; BMI 25.5 +/- 2.9 kg/m2) and 13 non-obese (age 8.4 +/- 0.9 y; BMI 16.9 +/- 1.2 kg/m2) prepubescent children, matched to the obese children for gender, age and height. MEASUREMENTS: Height and weight were measured to calculate BMI. Static weight-bearing footprints for the right and left foot of each subject were recorded using a pedograph to calculate the footprint angle and the Chippaux - Smirak index as representative measures of the surface area of the foot in contact with the ground. Right and left foot plantar pressures were then obtained using a mini-emed pressure platform to calculate the force and pressure experienced under each child's foot during static and dynamic loaded and unloaded conditions. RESULTS: Obese subjects displayed significantly lower footprint angle (t = 4.107; P = < 0.001) values and higher Chippaux-Smirak index values (t = -6.176; P = < 0.001) compared to their non-obese counterparts. These structural foot changes were associated with differences in plantar pressures between the two subject groups. That is, although rearfoot dynamic forces generated by the obese subjects were significantly higher than those generated by the non-obese subjects, these forces were experienced over significantly higher mean peak areas of contact with the mini-emed system. Therefore, rearfoot pressures experienced by the two subject groups did not differ. However, the mean peak dynamic forefoot pressures generated by the obese subjects (39.3 +/- 15.7 N(.)cm-2; q = 3.969) were significantly higher than those generated by the non-obese subjects (32.3 +/- 9.2 N(.)cm-2). CONCLUSIONS: It is postulated that foot discomfort-associated structural changes and increased forefoot plantar pressures in the obese foot may hinder obese children from participating in physical activity and therefore warrants immediate further investigation.