School of Exercise amd Nutrition Sciences, Deakin University, Burwood, Australia.
Health Promot J Austr. 2013 Apr;24(1):65-7. doi: 10.1071/HE12910.
Studies examining children's after-school physical activity (PA) and sedentary behaviours (SB) often use arbitrary times to signify the period start and end. A standardised time is required for future research examining this period. The aim of the present study was to compare children's after-school behaviour using three definitions of the after-school period, namely (1) end of school to 6 pm; (2) end of school to dinner time; and (3) end of school to sunset, to determine the extent of variability in PA and SB during the after-school period depending on the definition used.
Children (n=308; aged 8 years) from the Melbourne Transform-Us! intervention wore an accelerometer and a subsample (n=112) wore an activPAL inclinometer in 2010. The end of school bell time was obtained from the child's school, parents completed a 2-day log reporting their child's dinner time and sunset times were obtained from Geoscience Australia. ActiGraph accelerometers assessed the proportion of time spent sedentary (SED) and that spent in light (LPA), moderate (MPA) and moderate-to-vigorous (MVPA) PA during the three time periods; activPAL inclinometers assessed the proportion of time spent sitting (SIT).
Apart from the end of school time (3:30 pm), dinner (range 3:30 pm-8:40 pm) and sunset (range 5:07 pm-7:34 pm) times varied. Despite this, there were no significant differences in estimates of the proportions of time children spent in SED, LPA, MPA, MVPA or SIT between the three after-school periods examined.
Given the small differences in SED, PA and SIT during the after-school period regardless of the definition (6 pm, sunset or dinner time), it appears that applying a standardised definition of end of school to 6 pm is acceptable for defining children's PA and SB during the after-school period. So what? The use of a standardised after-school definition (end of school to 6 pm), will enable future studies exploring children's after-school PA and SB to be more comparable.
研究儿童课后体力活动（PA）和久坐行为（SB）的研究通常使用任意时间来表示时间段的开始和结束。未来研究这一时期需要一个标准化的时间。本研究的目的是比较三种定义的课后时间（即（1）放学后至 6 点；（2）放学后至晚餐时间；（3）放学后至日落）下儿童的课后行为，以确定使用不同定义时，课后时间内 PA 和 SB 的变化程度。
2010 年，来自墨尔本 Transform-Us！干预项目的 308 名儿童（年龄 8 岁）佩戴加速度计，其中 112 名儿童佩戴 activPAL 测斜仪。学校提供了放学铃声时间，家长填写了 2 天的日志，记录了孩子的晚餐时间，而日落时间则由澳大利亚地球科学局提供。ActiGraph 加速度计评估了三个时间段内的久坐时间（SED）和轻体力活动（LPA）、中等到剧烈体力活动（MVPA）的比例；activPAL 测斜仪评估了坐着时间（SIT）的比例。
除了放学时间（下午 3:30）外，晚餐时间（下午 3:30 至 8:40）和日落时间（下午 5:07 至 7:34）有所不同。尽管如此，在所检查的三个课后时间段中，儿童的 SED、LPA、MPA、MVPA 或 SIT 时间比例的估计值之间没有显著差异。
鉴于无论采用哪种定义（下午 6 点、日落或晚餐时间），课后时间内 SED、PA 和 SIT 的差异都很小，因此，采用标准化的放学后至下午 6 点的定义来定义儿童的课后 PA 和 SB 似乎是可以接受的。那又怎样？使用标准化的课后定义（放学后至下午 6 点）将使未来研究儿童课后 PA 和 SB 的研究更具可比性。
