Although there is an increasing awareness of the suitability of using compositional data methodology in public health research, classical methods of statistical analysis have been primarily used so far. The present study aims to illustrate the potential of robust statistics to model movement behaviour using Czech adolescent data. We investigated: (1) the inter-relationship between various physical activity (PA) intensities, extended to model relationships by age; and (2) the associations between adolescents' PA and sedentary behavior (SB) structure and obesity. These research questions were addressed using three different types of compositional regression analysis-compositional covariates, compositional response, and regression between compositional parts. Robust counterparts of classical regression methods were used to lessen the influence of possible outliers. We outlined the differences in both classical and robust methods of compositional data analysis. There was a pattern in Czech adolescents' movement/non-movement behavior-extensive SB was related to higher amounts of light-intensity PA, and vigorous PA ratios formed the main source of potential aberrant observations; aging is associated with more SB and vigorous PA at the expense of light-intensity PA and moderate-intensity PA. The robust counterparts indicated that they might provide more stable estimates in the presence of outlying observations. The findings suggested that replacing time spent in SB with vigorous PA may be a powerful tool against adolescents' obesity.

• Klíčová slova
• compositional data, compositional linear regression, log-ratio methodology, physical activity, pivot coordinates,
• MeSH
• chování mladistvých * MeSH
• cvičení * MeSH
• dítě MeSH
• lidé MeSH
• mladiství MeSH
• mladý dospělý MeSH
• obezita dětí a dospívajících etiologie   MeSH
• regresní analýza * MeSH
• sedavý životní styl * MeSH
• Check Tag
• dítě MeSH
• lidé MeSH
• mladiství MeSH
• mladý dospělý MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

BACKGROUND: The main aim of the study was to examine the cross-sectional associations between objectively measured physical activity (PA) and body fatness in 7-12-year-old children. METHODS: We performed an analysis of 365 children (209 girls). Participant recruitment was performed in eight randomly selected elementary schools in cities and towns with various numbers of inhabitants. The body composition analysis was performed according to a multi-frequency bioelectrical impedance analysis; PA was monitored using an accelerometer. RESULTS: In terms of the overall PA, boys were more active than girls. No significant associations (unadjusted and adjusted models) were found between light PA and all body fatness indicators in either sex. Moderate-to-vigorous PA was significantly negatively associated with all body fatness indicators only in girls. These associations strengthened after adjustment for age, height and sedentary time (β ranging from -0.49 to -0.36, P ≤ 0.01). In contrast, vigorous PA was strongly negatively associated with body fatness indicators only in boys. In the fully adjusted model the significant negative associations were found for fat mass percentage (β = -0.15, P = 0.048) and fat mass index (β = -0.15, P = 0.040). CONCLUSIONS: The present study suggests that increasing sex-specific PA of different intensities may be an appropriate approach for decreasing body fatness in children. Longitudinal studies are needed to verify these associations.

• Klíčová slova
• Body composition, Body fat distribution, Body mass index, Moderate-to-vigorous physical activity, Pediatric obesity,
• MeSH
• akcelerometrie MeSH
• cvičení * MeSH
• distribuce tělesného tuku * MeSH
• dítě MeSH
• lidé MeSH
• nitrobřišní tuk metabolismus   MeSH
• průřezové studie MeSH
• Check Tag
• dítě MeSH
• lidé MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Česká republika MeSH