Relationship Between Sedentary Behaviour And Body Mass Index,Physical Fitness Of Primary School And Junior Middle School Students In Shanghai

Research purposeThis study probes into the interrelationship between the sedentary behavior of children and adolescents,BMI and physical fitness.Research methodThe study sample were 720 children and adolescents from Jing'an,Jiading,Yangpu districts of Shanghai city.Participants were required to wear accelerometer 7days in succession for collecting the data of sedentary behavior and physical activity.Drawing on the 2014 revised Chinese National Student Physical Fitness Standard,the physical fitness of participants was graduated through tests.Likewise,the weight classification of participants acts according to the National Reference Norm for Overweight and Obesity established for the Chinese School-aged Male and Female Children aged 7 through 18 developed by Group of China Obesity Task Force.In addition,SPSS 20.0 was employed for data analysis.Normally distributed date was expressed as mean± standard deviation,while medians and quartile for abnormal data.For different gender groups,weight classification(normal and overweight groups)and physical fitness classification(pass and no pass groups,good and excellent groups),Mann-Whitney U test was used for analyzing the difference between sedentary behavior and physical activity levels.Wilcoxon analysis was applied for exploring the difference between sedentary behavior and physical activity levels of weekdays and weekends.For different behavior combinations,Kruskal-Wallis test was used for analyzing the difference between BMI and physical fitness level,Kendall's tau-b correlation analyzed the trend between sedentary behavior and BMI,physical fitness level.Multiple Regression Analysis was used for analyzing the correlation between sedentary behavior,BMI and physical fitness.The 5% level(2-tailed)was used as the statistical significance cutoff point.Research results(1)For the sedentary behavior,girls performed more than boys(44.2 vs45.8min/h,P<0.001).For the MVPA,boys were significantly higher than girls(3.0vs 2.3min/h,P<0.001).The sedentary behavior of the weekdays was significantly higher than the weekends(45.7 vs 45.0min/h,P=0.002).The MVPA of the weekdays was also significantly higher than the weekends(2.6 vs 2.2 min/h,P<0.001).The sedentary behavior of eight-grade students was higher than the four-grade(48.1 vs42.7min/h,P<0.001).However,the four-grade students engaged in more MVPA(2.7vs 2.4 min/h,P=0.001).(2)For the sedentary behavior,LPA,MPA,VPA and MVPA,there are no significant differences between normal and overweight groups.In terms of sedentary behavior,the physical fitness group(pass and no pass)is significantly higher than the group(good and excellent)(45.5 vs 44.4 min/h,P=0.008).Besides,good and excellent group participated more MVPA(0.9 vs 0.80 min/h,P=0.020).There is a positivegrowth trend between BMI and sedentary behavior,while the total score of physical fitness and sedentary behavior is opposite.(3)There was no significant difference between low SED/ high MVPA group(17.8kg/m2)and low SED/ low MVPA(17.5 kg/m2).But,both of them were significantly lower than high SED/ high MVPA group(19.6 kg/m2).Among low SED/ high MVPA group,low SED/ low MVPA group,high SED/ high MVPA group and high SED/ low MVPA group,there existed significant difference in terms of the physical fitness score(P=0.046).However,there was no significant difference between any two aforementioned groups.(4)The results of multivariable linear regression delineated that,sedentary behavior was positively correlated with BMI(? =0.138,P=0.002).However,sedentary behavior was negatively correlated with the total score of physical fitness(?=-0.136,P=0.005).When the physical activity was added as the mediate variable,the two mentioned relationships were disappeared.ConclusionsThe present research indicates that there existed too much sedentary behavior among Shanghai children and adolescents,accounting the three-fourths of the valid wearing time of accelerometer.Currently,the obvious trend of the sedentary behavior is that girls are higher than the boys,eight-grade students higher than the four-grade,weekdays higher than the weekends.The BMI of children and adolescents who possess less sedentary behavior and participate actively in the physical activity is lower than those who enjoys more sedentary behavior and inactively participate in the physical activity.Sedentary behavior is positively correlated with BMI,and negatively correlated with physical fitness.However,this relationship is closely related to physical activity.