Relationship Between Body Mass Index and Motor Competence in ChildrenAged 7-10 Years: A Cross-sectional Study

The prevalence of overweight and obesity in children is increasing, which is worrying because obese children are likely to become obese in adulthood and expose to its psychological consequences. To understand the cause of obesity in children, studies have investigated their physical activity (PA) profiles. Fundamental motor skills (FMS) have been known to be effective in children’s tendency to participate in PA. FMS is the building block of complex movements in sports, games, or participation in PA. Therefore, it is not surprising that their motor competence (MC) during childhood can predict their lifelong PA behaviors. The MC is defined as having skillful performance and improving the coordination, quality and basic control of movements in a wide range of PAs. With higher PA, children are more likely to have MC in FMS. According to the model proposed by Stodden et al. (2008), the synergistic correlation between PA and MC leads to positive (healthy weight status) or negative (unhealthy weight status) aspects of health. Body mass index (BMI) is also one of the other factors affecting children’s participation in PA. BMI is the most common way to estimate body weight. The correlation between BMI and children’s MC has not been reported in some studies. Considering these contradictory results, it is necessary to measure the correlation between children’s BMI and MC in FMS. This study aims to investigate this correlation of BMI, age, and gender with MC in FMS in children aged 7-10 years in Ahvaz, Iran.

This is a correlational study with a cross-sectional design. The study population consists of all children aged 7-10 years in Ahvaz city, out of whom 828 were selected by multi-stage cluster random sampling method. The test of gross motor development-3 (TGMD-3), a stadiometer (Seca model) with an accuracy of 0.1 cm, a digital scale (Seca model) with an accuracy of 0.1 kg were used to collect data, after receiving ethical approval (Code: IR.ABADANUMS.REC.1400.034), informed consent from the participants and their parents, and necessary arrangements with school principals, teachers, and trainers. BMI was calculated by dividing weight (kg) by height (meters squared). Then, the participants underwent TGMD-3 to measure motor skills. Pearson’s correlation test was used to analyze the relationship between MC in FMS and BMI. Two-way analysis of variance was used to investigate the effect of age and gender on the MC in FMS. The significance level was set at 0.05.

Results :

As shown in Table 1, the results of Pearson’s correlation test showed the significant relationship of BMI with the MC in locomotor skills (r=-0.179, P=0.001) and in total score of FMS (r=-0.070, P=0.045). In other words, children with a higher BMI had lower MC in locomotor skills and in total FMS. The results of Pearson’s correlation test showed no significant correlation of BMI with MC in ball skills (r=0.026, P=0.447).In locomotor skills, the results of two-way analysis of variance showed that the main effect of age was significant (F(818,3)=106.318, P=0.001, η2=0.281). The results of Bonferroni’s post-hoc test showed a significant difference between the MC of all age groups (P<0.05). The main effect of gender on MC in locomotor skills was not significant (F(818,1)=3.493, P=0.062, η2=0.004). The interaction effect of age and gender on MC in locomotor skills was not significant (F(818,3)=1.355, P=0.255, η2=0.005).In ball skills, the results of two-way analysis of variance showed that the main effect of age was significant (F(818,3)=218.784, P=0.001, η2=0.445). The results of Bonferroni’s post-hoc test showed a significant difference between the MC of all age groups (P<0.05). The main effect of gender on MC in ball skills was also significant (F(818,1)=140.842, P=0.001, η2=0.147). The interaction effect of age and gender on MC in ball skills was not significant (F(818,3)=0.115, P=0.952, η2=0.001).In total score of FMS, the results of two-way analysis of variance showed that the main effect of age was significant (F(818,3)=217.826, P=0.001, η2=0.444). The results of Bonferroni’s post-hoc test showed a significant difference between the MC of all age groups (P<0.05). The main effect of gender on MC in total FMS was also significant (F(818,1) =39.280, P=0.001, η2=0.046). The interaction effect of age and gender on MC in total FMS was not significant (F(818,3)=0.364, P=0.779, η2=0.001).

MC in FMS is needed for children’s participation in sports and various PAs. Based on the results of this study, the prevalence of overweight and obesity in children aged 7-10 in Ahvaz was high and worrying. A significant negative correlation was observed between children’s BMI and MC in locomotor skills and in total FMS, but no significant correlation was observed between their BMI and MC in ball skills. The main effect of age on the MC in locomotor skills, ball skills, and in total FMS was significant, which confirms the developmental nature of FMS. The main effect of gender was not significant on the MC in locomotor skills, but it was significant on the MC in ball skills and in total FMS, where girls had low MC compared to boys of the same age, indicating that they are at higher risk of delayed motor development. Therefore, it is recommended to improve their delayed motor development and MC in ball skills by developing appropriate interventions and providing opportunities to them to participate in PAs.