Objectives This study compared foot arch height, plantar fascia thickness, a range of motion assessments of the ankle joint, strength of the ankle joint, plantar pressure, and balance between obese and normal weight young adults. Methods Fifty-two participants were required for the present study design to achieve 80% power, 0.8 effect size (η2), and an alpha level of 0.05. The participants were categorized to normal weight or obese groups based on BMI (≤ 24 kg/m 2 and ≥ 25 kg/m 2 , respectively). The foot and ankle disability index and Sport survey were completed by the participants before the measurements. Foot arch height was measured using the navicular drop test, and plantar fascia thickness was measured using ultrasound. Plantar pressure and balance tests were also conducted, followed by ankle joint range of motion and strength tests. Results Foot arch height and plantar fascia thickness was significantly higher in the obese group compared with the normal weight group ( p < 0.01). There were significant differences in eversion of ankle strength, plantar pressure in the big toe and heel and anterior-posterior balance between normal and obese weight groups ( p < 0.05). Conclusion Obese young adults had more abnormalities in the medial longitudinal arch, plantar fascia, and plantar pressure as well as weakened ankle eversion strength and balance problems compared with the normal weight group.

There was lack of study which evaluated the effects of characteristics of subjects such as the body mass index (BMI) or waist circumference (WC), as well as sexual differences on trunk muscle activities. The purpose of the present study was to compare the abdominal muscle activities among the groups dividing criterion as the BMI, WC, and the gender. As a criterion of BMI and WC, subjects were arranged to three groups. Female subjects who were less than 25 kg/m2 BMI, and less than 90 WC were arranged as female with underweight group (FU), male subjects who were greater than 25 kg/m2 BMI and greater than 85 WC were arranged as male with overweight group (MO), male subjects who were less than 25 kg/m2 BMI and less than 85 WC were arranged in male with underweight group (MU). Surface electromyography responses of the rectus abdominis, internal oblique, external oblique muscles and lumbar level of erector spinae were obtained during the plank and maximal voluntary isometric contraction (MVIC). The MO group showed significantly higher %MVIC value of the internal oblique and lumbar level of erector spinae, compared to the MU group (P<0.05). The %MVIC of the rectus abdominis was significantly greater with the FU group (P<0.05). There were significant differences in the root mean squared (RMS) values from MVIC among the three groups (P<0.05). Regardless of muscles differences, the MO group showed significantly lower RMS activity values than the FU and the MU groups (P<0.05). Present study indicates some considerations of interpreting surface electromyography (sEMG) signal from region overlapping large fat tissue especially for trunk muscles. Individual characteristics such as gender, BMI, and WC could affect the sEMG signals. The female and male with overweight represent relatively high %MVICs during exercise, but it might be due to relatively low RMS values from procedure of MVICs.