Association between 24-hour activity behavior and cardiorespiratory endurance in children and adolescents based on isochronous substitution models
Objective To explore the comprehensive effect of 24-hour activity behavior on cardiorespiratory fitness(CRF)in children and adolescents and the practical effect of component isochronous substitution by component analysis,in order to provide scientific evidence for improving CRF in children and adolescents.Methods From May to June 2023,a total of 143 students from a junior high school in Tianjin were recruited in this study.ActiGraph GT3X+accelerometer was used to assess participants'24-hour activity behavior,and the fifth National Physical Fitness Monitoring Power Test Level 2 load experiment was conducted to test CRF.Compositional analysis was employed to analyze the relationships between different components and CRF,and a 15-minute isochronous substitution model was established to predict the impact of substituting various activity behaviors on outcome variables.Results For children aged 12-15,the average daily durations of moderate-to-vigorous physical activity(MVPA),light physical activity(LPA),sedentary behavior(SB),and sleep(SLP)were 49.91,146.31,643.19,and 600.59 minutes,respectively.The relative distribution of 24-hour activity behaviors in children and adolescents was closely associated with CRF,with MVPA showing relatively stable durations and the lowest probability of transitioning to other activity behaviors.Component results indicated that after controlling for age and gender,the proportion of time spent on MVPA(β=5.28,P＜0.01)was positively correlated with CRF,while the proportion of time spent on SB(β=-4.02,P＜0.01)was negatively correlated with CRF.In the 15-minute isochronous substitution model,replacing LPA,SB,and SLP with MVPA,as well as replacing SB with SLP,resulted in significant increases in CRF.Conversely,substituting MVPA with LPA,SB,and SLP led to a significant decrease in CRF.The dose-response relationship revealed an asymmetrical effect of isochronous substitution.With an increase in MVPA replacing other behaviors,the CRF levels in children and adolescents would gradually improve,while the opposite situation would lead to a rapid decline.Among the substitutions,MVPA replacing other behaviors for an average of 10 minutes per day yielded the most prominent effect.Conclusions Reducing SB while increasing MVPA is the best way to improve CRF in children and adolescents.It is recommended that students try to replace their original SB with MVPA as much as possible within the 10min recess to better promote CRF in children and adolescents.
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