中高强度身体活动量与肥胖儿童青少年心肺适能改善的剂量-效应关系研究

Dose-Response Relationship between Moderate to Vigorous Physical Activities of and Cardiorespiratory Fitness of Obese Children and Adolescents

目的:探讨每日中高强度身体活动(MVPA)量与肥胖儿童青少年心肺适能改善效果间的剂量-效应关系.方法:从封闭式训练营随机招募到65名肥胖儿童青少年,通过为期4周的运动干预,观察心肺适能改善情况.心肺适能采用20 m往返跑测试估算的最大摄氧量(VO_(2max))反映;静息能耗通过气体代谢分析仪测定;在营期间MVPA量采用ActiGraph GT3X+三轴运动加速度计监测,根据受试者每日MVPA量的三分位数,按照从低到高顺序分为Q1~Q3组.采用配对样本t检验比较组内干预前后心肺适能的差异,单因素方差分析比较组间心肺适能改善效果的差异,线性回归探讨MVPA量与心肺适能改善效果的量效关系,限制性立方样条(RCS)探讨MVPA量与心肺适能改善效果是否存在非线性关系.结果:共56名肥胖儿童青少年纳入统计分析.与干预前相比,干预后VO_(2max)整体显著改善(P<0.05);不同MVPA剂量组VO_(2max)的改善效果存在显著差异(P<0.05),线性回归结果显示MVPA量每增加1 min/d,VO_(2max)改善效果增加0.04 ml/kg/min(95%CI:0.008,0.065).RCS结果显示MVPA量与VO_(2max)改善效果之间存在非线性关系(P-Nonlinear<0.05);校正年龄、性别、基线BMI和基线VO_(2max)等因素后,MVPA≤98.9 min/d时,MVPA每增加1 min/d,VO_(2max)改善效果增加0.11 ml/kg/min(95%CI:0.052,0.166);当MVPA>98.9 min/d时,MVPA量的增加并不能显著增加VO_(2max)改善效果.结论:MVPA量与肥胖儿童青少年心肺适能改善效果间存在非线性的剂量-效应关系和阈值效应.在一定范围内,MVPA量与心肺适能改善效果存在量化关系,增加MVPA量可带来更高的心肺适能改善效果;但当MVPA量超过98.9 min/d时,心肺适能的改善效率会下降.

Objective To explore the dose-response relationship between daily the moderate-intensity to vigorous physical activity(MVPA)and cardiorespiratory fitness improvement of obese children and adolescents.Methods Sixty-five obese children and adolescents were randomly recruited from a training camp and observed their improvements in cardiorespiratory fitness after a 4-week exercise intervention.The cardiorespiratory fitness was measured by the maximal oxygen uptake(VO_(2max))in the 20-m shuttle run and the resting energy consumption was measured by a gas metabolism analyzer.Meanwhile,MVPA during the camp was monitored using the ActiGraph GT3X+three-axis exercise accelerometer and the amount of MVPA was divided into Q1~Q3 groups from the lowest to the highest.Paired samples ttest was used to compare the difference in cardiorespiratory fitness before and after the intervention.One-way analysis of variance was employed to compare the improvement in the cardiorespiratory fitness between groups.Moreover,the linear regression was employed to explore the dose-effect relationship between the amount of MVPA and the improvement in the cardiorespiratory fitness,while the restricted cubic spline(RCS)was used to observe whether there was non-linear relationship between the amount of MVPA and cardiorespiratory fitness.Results A total of 56 obese children and adolescents were included in the final statistical analysis.After the intervention,the average overall VO_(2max)improved significantly(P<0.05)and there were significant differences in the improvement of VO_(2max)among groups with different amounts of MVPA(P<0.05).According to the linear regression,the average VO_(2max)increased by 0.04 ml/kg/min(95%CI:0.008,0.065)for every 1 min/d increase of MVPA amount.The RCS results showed that there was a non-linear relationship between the daily MVPA amount and the improvement in the average VO_(2max)(P-Nonlinear<0.05).After adjusting factors such as age,gender,as well as baseline BMI and VO_(2max),when MVPA≤98.9 min/d,for each 1 min/d increase in the amount of MVPA,the average VO_(2max)increased by 0.11 ml/kg/min(95%CI:0.052,0.166),but when MVPA>98.9 min/d,no significant increase was observed in the average VO_(2max)with the increase of the MVPA amount.Conclusion There is a nonlinear dose-response relationship and threshold effect between the amount of MVPA and improvement in the cardiorespiratory fitness of obese children and adolescents.Within a certain range,there is a quantitative relationship between them,and increasing the amount of MVPA can bring about a significant improvement in cardiorespiratory fitness.However,when the amount of MVPA exceeds 98.9 min/d,the improvement in the cardiorespiratory fitness will not be significant.