Background: A high load on children 's feet can cause arch deformation and negatively affect their normal development. Studies have yet to document how the foot arch varied with different body mass index (BMI) increments and its influence on foot loading patterns.
Methods: Barefoot walking trails were conducted using a Footscan® plate system. A follow-up check was performed after twenty-four months. Participants were selected with an initial BMI between 14.5 kg/m2 and 16.5 kg/m2. Totally 75 participants were classified into groups 0-7 according to the BMI increment levels of 0-0.49 kg/m2, 0.50-1.49 kg/m2, 1.50-2.49 kg/m2, 2.50-3.49 kg/m2, 3.50-4.49 kg/m2, 4.50-5.49 kg/m2, 5.50-6.49 kg/m2, 6.50-7.49 kg/m2, respectively. Paired t-tests and effect sizes were used to compare the data.
Results: The arch index significantly decreased when the BMI reached 20.8 kg/m2. Significantly increased normalized maximum forces were found in the great toe and 1st MTPJ in groups 4-5. Meanwhile, the absence of significance showed under the 3rd-5th, midfoot, and rearfoot in those groups. The normalized maximum force increments under the 3rd-5th MTPJs, midfoot and rearfoot regions in groups 4-5 after the follow-up study were significantly decreased compared with the increments found in groups 0-3, followed by a sudden increase arising under those regions in group 6. It indicates a transition period that leads to alteration in gait pattern characteristics when BMI increases to 18.6-19.9 kg/m2 (between group 3 and group 4). Group 6 displayed significantly increased peak pressure amplitudes under the great toe, 1st-3rd MTPJs, midfoot, and medial rearfoot compared to other groups.
Significance: There was a transition period when the BMI of normal-weighted children increased to a certain extent and failed to reach the obesity level, resulting in changes in foot arch structure and loading patterns.
Keywords: BMI increment; Children; Foot loading patterns; Medial arch flattening; Obesity.
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