The Relationship Between Motor Competence,Physical Activity And Perceived Motor Competence In 7 To 10 Years School Children

Background:Childhood obesity is an increasingly serious public health problem worldwide.According to the Report on Nutrition and Chronic Diseases in China（2020）,the prevalence rate of overweight and obesity among Chinese children and adolescents is 19.0%.Early childhood overweight and obesity are important predictors of adolescent and even adult obesity.Physical Activity（PA）plays a crucial role in preventing overweight and obesity in children and adolescents and promoting physical and mental health of children.However,at present,Inadequate PA affects health more and more seriously,and only 8.9%of Chinese students can meet the recommended PA guidelines.A major factor restricting PA is Motor Competence（MC）.MC is the basis of PA for children and adolescents.MC practice in early childhood can improve children’s enthusiasm to participate in sports activities,increase PA time,and promote physical health and social interaction.In the MC development stage of children and adolescents,PMC(Perception Motor Competence（PMC）participates in and influences the confidence and persistence of children and adolescents in learning skills,namely,PMC affects children and adolescents’MC development and PA level.According to Harter’s competency motivation theory,PMC and MC are important factors that can predict future PA in children.According to the model related to MC,PA and Body weight state proposed by Stodden et al in 2008,MC,PMC and health-related physical fitness are the main mechanism involved in PA.Therefore,to explore the causal relationship between MC,PA,PMC and Body Mass Index（BMI）and complement the evidence chain of current studies,It is very important to provide research basis for follow-up intervention research.Objective:（1）The objective measurement of PA,MC,PMC and BMI variables was conducted to explore the changing trend of variables in school children aged 7 to10 years with the increase of age,so as to provide guidance for improving children’s PA level and reaching the recommended amount of PA guidelines.（2）Explore the correlation between PA,MC,PMC and BMI variables to supplement the insufficient evidence of current research.（3）Explore the mechanism of action between PMC and PA,and provide reference suggestions for sports workers to formulate intervention programs for school-age children’s MC development.（4）Based on the one-year follow-up study,the causal relationship between various variables in school children aged 7 to 10 years was explored,providing reference for the physical health work of Chinese school children aged 7 to 10 years.Methods:A total of 405 children aged 7～10 years old were randomly selected from 9 classes in a primary school in Shijiazhuang City,including 210 boys and 195girls,145 in grade 1（7～8 years old）,136 in grade 2（8～9 years old）and 124 in grade 3（9～10 years old）.The collection time of pre-test and post-test data is shown as T1and T2,respectively.Descriptive statistics were used to analyze children’s basic information,family socioeconomic status,MC,PA,BMI and PMC.Independent sample T test was used to analyze the gender differences of the above variables.Univariate variance analysis of the above variables age difference;Repeated measurement variance was used to test the gender difference between the pre and post tests in each grade.After controlling demographic factors and family economic status,the correlation between MC,PA,BMI and PMC was analyzed by multiple linear regression.Mplus Editor 8.0 software was used to process the data.SEM was used to test the mediating effect of explicit variable PMC.5000 was selected from Bootstrap and model 4 was selected.Cross-lag was used to test the longitudinal correlations among MC,PA,BMI and PMC at T1 and T2 time points.The fitting index standard of the model test was CFI>0.90,TLI>0.90,RMSEA<0.10,SRMR<0.08 represents good model fitting with P<0.05 was considered statistically significant.Results:（1）The basic information of the tested children showed that Han ethnic group accounted for 99.3%,urban children accounted for 98.1%;27.7 per cent and 42.5 per cent of parents have received higher education,while the majority of children have parents with lower education levels;Gender differences of ethnic group,residence,parental education and family income were not statistically significant（P>0.05）.The BMI at T1 was 16.45±3.33kgm²,MVPA 31.44±14.50min/d,MC73.67±6.78 points and PC 2.61±0.51 points.The results showed that the gender differences of BMI,MVPA and MC at T1 were statistically significant（P<0.01;P<0.001）.（2）MC:Among the three grades,the improvement range of body displacement ability of boys is higher than that of girls,but the improvement range of ball control ability of girls is better than that of boys,and the improvement range of TGMD total score of girls is also better than that of boys.There is only age difference in body displacement ability of first grade（P<0.05）;PA:Both LPA,MVPA and TPA decreased to varying degrees,except for LPA of boys in grade 1 and MVPA of boys and TPA of girls in Grade 2.In the process of growth and development,there was no significant difference in PA with the increase of age,but the difference in gender was statistically significant（P<0.001）;PMC:The increase of boys and girls in grade 1 was4.24%and 0.77%,respectively;The increase rate of boys and girls in grade two was2.76%and 1.50%respectively.The increase of boys and girls in the third grade was5.30%and 3.83%,respectively.After one year of natural growth and development,the gender difference of PMC score was statistically significant（P<0.001）,but the age difference was not statistically significant（P>0.05）.（3）The linear regression model showed that after controlling for demographic factors,family socioeconomic status and BMI,locomotor skill（B=0.41,P<0.05,R²=13.2%）,ball skill（B=0.30,P<0.05,R²=13.3%）and TGMD-3 total（B=0.28,P<0.05,R²=13.8%）had significant effects on PA.locomotor skill（B=0.02,P<0.05,R²=8.0%）,ball skill（B=0.02,P<0.001,R²=10.5%）and TGMD-3 total（B=0.16,P<0.001,R²=10.7%）had significant effect on PMC.PMC had no significant effect on PA（B=-0.46,P>0.05,R²=12.4%）.After controlling for demographics and family socioeconomic status,PBF（B=-0.12,P<0.001,R²=20.5%）and BMI（B=-0.23,P<0.05,R²=19.0%）had significant effect on MC.（4）In the relationship between MC and PA,MC explained 1.8%of the variance of PA,total effect:B=0.221,P<0.05,95%CI（0.029,0.432）,excluding 0,indicating that the total effect of MC on PA exists.The direct effect of MC on PA was B=0.256,P<0.05,95%CI（0.057,0.467）,excluding 0,indicating that MC has a direct positive effect on PA,and the proportion of direct effect of MC on MVPA is 15.9%.The indirect effect of MC on PA is B=-0.035,P>0.05,95%CI（-0.086,0.006）,confidence interval passing 0,indicating that indirect effect does not exist,so PMC does not exist in the relationship between MC and PA.（5）In the relation between PA and MC,PA explained 5.7%of the variance of MC,and the total effect was B=0.052,P<0.05,95%CI（0.006,0.097）,excluding 0,indicating that the total effect of PA on MC exists.The direct effect of MC on PA was B=0.057,P<0.05,95%CI（0.027,0.210）,excluding 0,indicating that MC has a direct positive effect on PA,and the proportion of direct effect of MC on PA is 11.3%.The indirect effect of MC on PA is B=-0.022,P>0.05,95%CI（-0.017,0.004）,confidence interval passing 0,indicating that indirect effect does not exist,so the mediating effect of PMC in the relationship between PA and MC does not exist.（6）In the cross-lag test,T1 time MC significantly predicted T2 time PA（B=0.224,P<0.001）;T1 time MC significantly predicted T2 time BMI（B=-0.242,P<0.001）;T1 time MC significantly predicted T2 time PMC（B=0.282,P<0.001）.T1time PA significantly predicted T2 time BMI（B=-0.081,P<0.05）;T1 time PA significantly predicted T2 time PMC（B=0.155,P<0.001）.T1 time BMI significantly predicted T2 time MC（B=0.131,P<0.05）;T1 time BMI significantly predicted T2time PA（B=-0.106,P<0.05）;T1 time BMI significantly predicted T2 time PMC（B=-0.150,P<0.01）.（7）In cross-lag test,T1 time MC significantly predicted T2 time PA(B=0.173,P_male<0.01;B=0.328,P_female<0.01);T1 time MC significantly predicted T2 time BMI(B=-0.186,P_male<0.001;B=-0.310,P_female<0.001);T1 time MC significantly predicted T2 time PMC(B=0.265,P_male<0.001;B=0.334,P_female<0.001).There was no statistically significant cross-lag effect between PA at T1 and BMI and PMC at T2（P<0.05）.T1 time BMI significantly predicted T2 time MC(B=0.182,P_male<0.01);T1 time BMI significantly predicted T2 time PMC(B=-0.195,P_male<0.01).Conclusions:（1）The body displacement ability,ball manipulation ability and TGMD total score of school children aged 7 to 10 years were significantly positive predictors of PA and PMC;BMI and PBF significantly negatively predicted MC.The mediating effect of PMC between MC and PA does not exist.（2）There was a causal relationship between MC and BMI,PA and BMI in school children aged 7-10 years.MC can predict PA and PMC positively and BMI negatively.PA can positively predict PMC and negatively predict BMI.Suggestions:（1）For school children aged 7 to 10 years old,at least 60 minutes of medium to high intensity physical activity can be conducted every day after school,in order to reduce the adverse impact of insufficient physical activity on weight.For some overweight and obese school children,they can learn different sports to make them far away from the comfort zone,participate in sports,and finally reduce BMI,PBF and other indicators to achieve a healthy state.（2）The relevant departments in our country should stipulate schools,families and communities to supervise sports for children in the future,to ensure that children master at least one ball and track and field events,to ensure learning time and improve children’s physical health.