1. Introduction
n the world of biomechanics, an increase in Body Mass Index (BMI) is associated with aberrations in gait and an increase in the forces of the whole body, especially the lower limbs that bear weight [1]. On the other hand, obesity and overweight lead to decreased range of motion of the knee increased osteoarthritis, reduced stride length, increased joint wear, and changes in gait [2]. Nevertheless, it is unclear what effect BMI has on maintaining balance and symmetry in the feet’ soles. While maintaining balance and symmetry of the sole is a critical factor in performing daily activities and weight-bearing activities [6, 5, 4, 3]. 
The symmetry between the lower limbs is fundamental in performing sports movements [7, 8]. Besides, it has been reported that balance between the preferred and non-preferred foot may prevent muscle imbalance and prevent sports injuries [9, 10]. Because the right and left sides of the body are different, it may be thought that the parameters of the sole of the preferred foot may differ from those of the non-preferred foot. The feet soles provide comprehensive information about the symmetry between the feet [11, 12]. This may offer appropriate rehabilitation programs to prevent lower limb imbalance and maintain proper posture [5, 13, 14]. Therefore, this study aimed to investigate the symmetry of preferred and non-preferred foot of young girls with different BMI when standing on two legs.
2. Materials and Methods
The present research method was quasi-experimental, and the research design was comparative with the control group and the type of applied research. The statistical sample consisted of 42 people for both groups using Power ×G software [15], but 44 people were selected to enter the study to prevent a drop in the number of people. Of these, 22 were selected as an overweight group with 25≥ BMI (kg/m2) <30 and 22 with 18.5≥ BMI (kg/m2) <25 for the normal weight group. The research ethics committee approved the research protocol, and informed consent was obtained from the individuals. First, the height and weight of the subjects were taken, and the BMI was calculated. Then, the subjects’ preferred foot was determined using the ball impact test [16]. 
Subjects were placed on a pedoscope [17] and asked to look at a fixed point on the wall at a distance of 3 m and stand with bare feet so that the distance between the legs is 8 cm when standing, and three 20-second testing sessions with 15 seconds rest between each test were performed. The symmetry index was obtained from the ratio of the variables of the sole of the right foot divided by the left foot [18, 19]. The mean of the received data was recorded as an individual’s record for further calculations. The Kolmogorov-Smirnov test was used to check the normality of data distribution. The Levene test was used to prevent group matching. An Independent inferential t-test was used to compare inter-group results, and paired t-test was used to compare intra-group results. Tests were analyzed at a significance level of 0.05 using SPSS software v. 24.
3. Results
The subjects’ demographic characteristics showed that the participating groups were homogeneous in terms of age and height but differed in weight and BMI, divided into two groups. The overweight group had the Mean±SD age of 22.41±3.42, the Mean±SD BMI was 26.78±1.67, and the average weight group had the Mean±SD age of 21.41±1.37, and the Mean±SD BMI was 21.35±1.38. The Kolmogorov-Smirnov test was not significant for checking the normality of variables (P≥0.05). The independent t-test, symmetry index in overweight, and control groups (Table 1) did not show a significant difference in symmetry indices (P≥0.05). 


4. Discussion and Conclusion
The present study aimed to investigate the symmetry of preferred and non-preferred foot of young girls with different BMI. The symmetry index of the preferred and non-preferred foot of the overweight group ranged from 0.72 to 1.41, and in the normal group was 0.76 to 1.43, but the results did not differ significantly (P>0.05). Some researchers examined the symmetry of the preferred and non-preferred foot when walking [31, 32], and in line with our results, it was found that there is no significant difference between the preferred and non-preferred foot. In contrast, in another study [33], the asymmetry between the preferred and non-preferred foot in different gait parameters was found to be inconsistent with our investigation. Among the reasons for inconsistency with this research, we can mention the selected variables to study symmetry, including spatial-temporal and kinetic variables. 
Dağ et al. examined the symmetry of preferred and non-preferred foot of taekwondo athletes, and their results did not show a significant difference in line with the results of the present study [35]. Sforza et al. examined the analysis of coordination symmetry of the feet of healthy young people. They were consistent with the current study results and observed high symmetry between both legs in individuals, and the symmetry index of women was higher than men [36]. The mechanisms of amplification or reduction that affect the foot’s symmetry are unknown. The use of more motor neurons in the dominant limb may be related to the greater need for energy production of the limb’s plantar flexor and greater motive force [37]. To this end, research should assess how an organ’s dominance affects the risk of injury and foot disorders, leading to preventive measures to eliminate subsequent complications and injuries of the foot.

Ethical Considerations
Compliance with ethical guidelines
This study was approved by the Ethics Committee of the University of Arak University of Medical Sciences (Code: IR.UMSHA.REC.1394.42). 

Funding
This research was supported by the research project (No. 467), Funded by the University of Arak University Research Council.

Authors' contributions
All authors contributed in preparing this article.

Conflicts of interest
The authors declared no conflict of interest.


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