Why are children different in their moderate-to-vigorous physical activity levels? A multilevel analysis

Objective: Children's differences in moderate-to-vigorous physical activity levels are not at random. This study investigates the relevance of individual- and school-level characteristics in explaining these differences. Methods: In total, 307 children (154 girls) aged 5–10 years, from 19 Portuguese schools, were sampled. Height and weight were measured, and body mass index was calculated. Time spent in moderate-to-vigorous physical activity was measured by accelerometry. Gross motor coordination was assessed with the KörperkoordinationsTest für Kinder battery and socio-economic status was obtained via the school social support system. School characteristics were obtained with an objective school audit. A multilevel analysis was used as implemented in Stata 15. Results: Schools explained 18.2% of the total variance in moderate-to-vigorous physical activity, with the remainder being ascribed to children's distinct characteristics. Boys were more active (β = 29.59 ± 11.52, p < 0.05), and having higher gross motor coordination levels (β = 0.11 ± 0.04, p < 0.05) was positively associated with daily moderate-to-vigorous physical activity, whereas being older (β = −5.00 ± 1.57, p < 0.05) and having higher socio-economic status (β = −7.89 ± 3.12, p < 0.05) were negatively related with moderate-to-vigorous physical activity. From the school-level correlates, only playground dimension was significantly associated with moderate-to-vigorous physical activity levels. Children from schools with medium (40 m² to 69 m²) and large playground dimensions (≥70 m²) were less active than children with smaller playground dimensions (10 m² to 39 m²). Conclusions: Variation in school children's moderate-to-vigorous physical activity is mostly explained by their individual characteristics; school characteristics also play a role but to a smaller degree. Future intervention programs to change this behavior should be more personalized, emphasizing mostly individual-level characteristics.