上海市中小学生身体活动、久坐行为与BMI的等时替代关系

Isotemporal Substitution Analysis for Physical Activity,Sedentary Behaviour and BMI among Primary and Middle School Students in Shanghai

目的:探究上海市中小学生身体活动和久坐行为时间替代与身体质量指数(BMI)的相关关系。方法:选取上海市486名6~16岁中小学生为测试对象,使用加速度计客观测量其身体活动和久坐行为水平,使用标准测量仪器测量身高和体重;采用单因素模型、分配模型和等时替代模型3种数据分析方法进行数理统计。结果:平均每天用5 min的中高强度身体活动(MVPA)替代久坐行为和低强度身体活动(LPA)可分别使初中生BMI减少0.194 kg/m^(2)和0.207 kg/m^(2),使正常体重学生BMI减少0.118 kg/m^(2)和0.108 kg/m^(2),使超重肥胖学生BMI减少0.151 kg/m^(2)和0.147 kg/m^(2)。平均每天用5 min的MVPA和LPA替代久坐行为后,可使小学生BMI分别减少0.167 kg/m^(2)和0.035 kg/m^(2)。久坐行为替代初中生、正常体重和超重肥胖学生MVPA及替代小学生的LPA和MVPA均显著提高了其BMI水平。其他行为替代方式与BMI未见显著相关关系。结论:不同活动行为与BMI的等时替代关系存在学段差异和体重状态差异,MVPA替代久坐行为与LPA有利于初中生的肥胖防控,MVPA和LPA替代久坐行为可有效降低小学生的BMI。MVPA替代久坐行为与LPA均有利于正常体重和超重肥胖学生的体重控制,但对超重肥胖学生的降重效应大于正常体重学生。运动指南和肥胖干预策略的制定需综合考量活动行为的相互影响,为不同学段和体重状态的学生提供有针对性的时间重新分配建议。

Objective:To explore the isotemporal substitution association between physical activity and sedentary behaviour and body mass index(BMI)among primary and middle school students in Shanghai.Methods:A sample of 486 primary and middle school students aged 6-16 years old were selected.Physical activity and sedentary behaviour were objectively measured by accelerometers.Height and weight were measured using standard measuring instruments.The single models,partition models,and isotemporal substitution models were used.Results:Substituting 5 min of sedentary behaviour or light physical activity(LPA)with moderate-to-vigor-ous physical activity(MVPA)were associated with a lower BMI of middle school students by 0.194 kg/m^(2)and 0.207 kg/m^(2),a lower BMI of normal weight students by 0.118 kg/m^(2)and 0.108 kg/m^(2),and a lower BMI of overw-eight/obesity students by 0.151 kg/m^(2)and 0.147 kg/m^(2),respectively.Substituting 5 min of sedentary behaviour with MVPA or LPA were associated with a lower BMI of primary school students by 0.167 kg/m^(2)and 0.035 kg/m^(2),respectively.Sedentary behaviour replaced MVPA among middle school students,normal weight students,and overweight/obesity students and it replaces LPA or MVPA among primary school students,which were significa-ntly increased their BMI.Other isotemporal substitution methods did not show a significant correlation with BMI.Conclusion:There are school stage and weight status differences in the relationship between activity beha-viour and BMI.Substituting sedentary behaviour or LPA with MVPA is beneficial to the prevention and control of obesity among middle school students,and the substitution of sedentary behavior with MVPA and LPA can effectively reduce the BMI of primary school students.Substituting sedentary behavior or LPA with MVPA was beneficial to the weight control of normal weight and overweight and obese students,but the weight loss effect of overweight and obese students was greater than that of normal weight students.The development of exercise guidelines and obesity intervention strategies should comprehensively consider the interaction of activity behavi-our and provide targeted time use suggestions for students with different school stages and weight statuses.