Nader Philip R, Bradley Robert H, Houts Renate M, McRitchie Susan L, O'Brien Marion
Department of Pediatrics, University of California San Diego, 9500 Gilman Dr, La Jolla, CA 92093-0927, USA.
JAMA. 2008 Jul 16;300(3):295-305. doi: 10.1001/jama.300.3.295.
Decreased physical activity plays a critical role in the increase in childhood obesity. Although at least 60 minutes per day of moderate-to-vigorous physical activity (MVPA) is recommended, few longitudinal studies have determined the recent patterns of physical activity of youth.
To determine the patterns and determinants of MVPA of youth followed from ages 9 to 15 years.
DESIGN, SETTING, AND PARTICIPANTS: Longitudinal descriptive analyses of the 1032 participants in the 1991-2007 National Institute of Child Health and Human Development Study of Early Child Care and Youth Development birth cohort from 10 study sites who had accelerometer-determined minutes of MVPA at ages 9 (year 2000), 11 (2002), 12 (2003), and 15 (2006) years. Participants included boys (517 [50.1%]) and girls (515 [49.9%]); 76.6% white (n = 791); and 24.5% (n = 231) lived in low-income families.
Mean MVPA minutes per day, determined by 4 to 7 days of monitored activity.
At age 9 years, children engaged in MVPA approximately 3 hours per day on both weekends and weekdays. Weekday MVPA decreased by 37 minutes per year [corrected], while weekend MVPA decreased by 39 minutes per year [corrected]. By age 15 years, adolescents were only engaging in MVPA for 50 minutes per weekday [corrected] and 36 minutes per weekend day [corrected]. Boys were more active than girls, spending 18 and 14 more minutes per day [corrected] in MVPA on the weekdays and weekends, respectively. The rate of decrease in MVPA was the same for boys and girls. The estimated age at which girls crossed below the recommended 60 minutes of MVPA per day was approximately 13.2 years for weekday [corrected] activity compared with boys at 14.9 years [corrected], and for weekend activity, girls crossed below the recommended 60 minutes of MVPA at 12.7 years [corrected] compared with boys at 13.6 years [corrected].
In this study cohort, measured physical activity decreased significantly between ages 9 and 15 years.
身体活动减少在儿童肥胖率上升中起着关键作用。尽管建议每天至少进行60分钟的中等到剧烈身体活动（MVPA），但很少有纵向研究确定青少年近期的身体活动模式。
确定9至15岁青少年MVPA的模式和决定因素。
设计、地点和参与者：对1991 - 2007年美国国立儿童健康与人类发展研究所早期儿童保育与青少年发展出生队列研究中10个研究地点的1032名参与者进行纵向描述性分析，这些参与者在9岁（2000年）、11岁（2002年）、12岁（2003年）和15岁（2006年）时通过加速度计测定了MVPA的分钟数。参与者包括男孩（517名[50.1%]）和女孩（515名[49.9%]）；76.6%为白人（n = 791）；24.5%（n = 231）生活在低收入家庭。
通过4至7天的监测活动确定的每天MVPA平均分钟数。
9岁时，儿童在周末和工作日每天进行MVPA约3小时。工作日MVPA每年减少37分钟[校正后]，而周末MVPA每年减少39分钟[校正后]。到15岁时，青少年在工作日每天仅进行MVPA 50分钟[校正后]，周末每天进行36分钟[校正后]。男孩比女孩更活跃，在工作日和周末每天在MVPA上分别多花费18分钟和14分钟[校正后]。男孩和女孩MVPA的下降速度相同。对于工作日活动，估计女孩每天MVPA低于建议的60分钟的年龄约为13.2岁[校正后]，而男孩为14.9岁[校正后]；对于周末活动，女孩在12.7岁[校正后]时MVPA低于建议的60分钟，而男孩为13.6岁[校正后]。
在本研究队列中，9至15岁期间测量的身体活动显著减少。
