Department of Health & Kinesiology, University of Utah, Salt Lake City, UT 84112, USA.
Int J Environ Res Public Health. 2021 Mar 21;18(6):3243. doi: 10.3390/ijerph18063243.
The purpose of this study was to apply compositional data analysis (CoDA) for the analysis of segmented school step counts and associate the school step count composition to body mass index (BMI) z-scores in a sample of children. Participants were 855 (51.8% female) children recruited from the fourth and fifth grades from four schools following a 7-h school schedule. Using piezoelectric pedometers, step count data were collected during physical education, recess, lunch, and during academic class time. A multi-level mixed effects model associated the step count composition with BMI z-scores. Compositional isotemporal substitution determined changes in BMI z-scores per reallocation of steps between pairs of school segments. A higher percentage of steps accrued during physical education (b = -0.34, 95%CI: -0.65--0.03, = 0.036) and recess (b = -0.47, 95%CI: -0.83--0.11, = 0.012), relative to other segments, was associated with lower BMI z-scores. Specifically, a 5% to 15% reallocation of steps accrued during lunchtime to either physical education or recess was associated with lower BMI z-scores, ranging from -0.07 to -0.25 standard deviation units. Focusing school-based promotion of physical activity during physical education and recess may have greater relative importance if targeted outcomes are weight-related.
本研究旨在应用成分数据分析（CoDA）分析分段的学校步数，并将学校步数组成与 BMI z 分数相关联，研究对象为 855 名（51.8%为女性）儿童，他们来自于四所学校的四至五年级，遵循 7 小时的学校日程安排。使用压电计在体育课、课间休息、午餐和学术课时收集步数数据。采用多级混合效应模型将步数组成与 BMI z 分数相关联。成分等时替代法确定了在重新分配特定学校时段之间的步数时，BMI z 分数的变化。与其他时段相比，体育课（b = -0.34，95%CI：-0.65--0.03， = 0.036）和课间休息（b = -0.47，95%CI：-0.83--0.11， = 0.012）累计的较高比例的步数与较低的 BMI z 分数相关。具体来说，将午餐时间累计的 5%至 15%的步数重新分配到体育课或课间休息中，与 BMI z 分数降低 0.07 至 0.25 个标准差单位有关。如果以体重相关的目标为重点，那么在体育课和课间休息期间集中开展学校体育活动的促进可能具有更大的相对重要性。
