Arundell Lauren, Hinkley Trina, Veitch Jenny, Salmon Jo
Centre for Physical Activity and Nutrition Research, School of Exercise and Nutrition Sciences, Faculty of Health, Deakin University, Burwood, Australia.
PLoS One. 2015 Oct 30;10(10):e0140132. doi: 10.1371/journal.pone.0140132. eCollection 2015.
Children's after-school physical activity (PA) and sedentary behaviours (SB) are not well understood, despite the potential this period holds for intervention. This study aimed to describe children's after-school physical activity and sedentary behaviours; establish the contribution this makes to daily participation and to achieving physical activity and sedentary behaviours guidelines; and to determine the association between after-school moderate- to vigorous-intensity physical activity (MVPA), screen-based sedentary behaviours and achieving the physical activity and sedentary behaviour guidelines.
Children (n = 406, mean age 8.1 years, 58% girls) wore an ActiGraph GT3X accelerometer. The percentage of time and minutes spent sedentary (SED), in light- physical activity (LPA) and MVPA between the end-of-school and 6pm (weekdays) was calculated. Parents (n = 318, 40 years, 89% female) proxy-reported their child's after-school participation in screen-based sedentary behaviours. The contribution that after-school SED, LPA, MVPA, and screen-based sedentary behaviours made to daily levels, and that after-school MVPA and screen-based sedentary behaviours made to achieving the physical activity/sedentary behaviour guidelines was calculated. Regression analysis determined the association between after-school MVPA and screen-based sedentary behaviours and achieving the physical activity/sedentary behaviours guidelines.
Children spent 54% of the after-school period SED, and this accounted for 21% of children's daily SED levels. Boys spent a greater percentage of time in MVPA than girls (14.9% vs. 13.6%; p<0.05), but this made a smaller contribution to their daily levels (27.6% vs 29.8%; p<0.05). After school, boys and girls respectively performed 18.8 minutes and 16.7 minutes of MVPA, which is 31.4% and 27.8% of the MVPA (p<0.05) required to achieve the physical activity guidelines. Children spent 96 minutes in screen-based sedentary behaviours, contributing to 84% of their daily screen-based sedentary behaviours and 80% of the sedentary behaviour guidelines. After-school MVPA was positively associated with achieving the physical activity guidelines (OR: 1.31, 95%CI 1.18, 1.44, p<0.05), and after-school screen-based sedentary behaviours were negatively associated with achieving the sedentary behaviours guidelines (OR: 0.97, 95%CI: 0.96, 0.97, p<0.05).
The after-school period plays a critical role in the accumulation of children's physical activity and sedentary behaviours. Small changes to after-school behaviours can have large impacts on children's daily behaviours levels and likelihood of meeting the recommended levels of physical activity and sedentary behaviour. Therefore interventions should target reducing after-school sedentary behaviours and increasing physical activity.
尽管儿童放学后的身体活动（PA）和久坐行为（SB）这一时期具有干预潜力，但目前对此了解不足。本研究旨在描述儿童放学后的身体活动和久坐行为；确定其对日常活动参与以及达到身体活动和久坐行为指南的贡献；并确定放学后中等至剧烈强度身体活动（MVPA）、基于屏幕的久坐行为与达到身体活动和久坐行为指南之间的关联。
儿童（n = 406，平均年龄8.1岁，58%为女孩）佩戴ActiGraph GT3X加速度计。计算放学至下午6点（工作日）期间久坐（SED）、轻度身体活动（LPA）和MVPA所花费的时间百分比和分钟数。家长（n = 318，40岁，89%为女性）通过代理报告其孩子放学后参与基于屏幕的久坐行为的情况。计算放学后SED、LPA、MVPA以及基于屏幕的久坐行为对每日水平的贡献，以及放学后MVPA和基于屏幕的久坐行为对达到身体活动/久坐行为指南的贡献。回归分析确定放学后MVPA与基于屏幕的久坐行为以及达到身体活动/久坐行为指南之间的关联。
儿童放学后54%的时间处于久坐状态，这占其每日久坐水平的21%。男孩在MVPA中花费的时间百分比高于女孩（14.9%对13.6%；p<0.05），但这对其每日水平的贡献较小（27.6%对29.8%；p<0.05）。放学后，男孩和女孩分别进行了18.8分钟和16.7分钟的MVPA，分别占达到身体活动指南所需MVPA的31.4%和27.8%（p<0.05）。儿童花96分钟进行基于屏幕的久坐行为，占其每日基于屏幕的久坐行为的84%以及久坐行为指南的80%。放学后MVPA与达到身体活动指南呈正相关（OR：1.31，95%CI 1.18，1.44，p<0.05），放学后基于屏幕的久坐行为与达到久坐行为指南呈负相关（OR：0.97，95%CI：0.96，0.97，p<0.05）。
放学后这段时间在儿童身体活动和久坐行为的积累中起着关键作用。放学后行为的微小变化可能对儿童的日常行为水平以及达到推荐的身体活动和久坐行为水平的可能性产生重大影响。因此，干预措施应旨在减少放学后的久坐行为并增加身体活动。
