OBJECTIVES: The objective of this study was to identify typologies of activity-related behaviours during adolescence and to explore transitions between the identified typologies. Additionally, we aimed to identify demographic indicators associated with the transitions and typology membership. DESIGN: Prospective cohort study. SETTING: Czech Republic. PARTICIPANTS: Individuals involved in the Czech part of the European Longitudinal Study of Pregnancy and Childhood study, aged 11 to 18 years. The study involved over 563 individuals, of whom 380 provided complete data for the analysis. PRIMARY OUTCOME MEASURES: Time spent outdoors, participation in organised physical activity (PA) and sport activities, time spent watching television and using a personal computer, and total sleep duration at ages 11, 15 and 18 years. Typologies were identified using Latent Transition Analysis. RESULTS: Four typologies of activity-related behaviours were identified and labelled to reflect their behavioural profiles: (1) Actives (high outdoor time and organised PA and sport participation, low screen time and optimal sleep duration); (2) Active screeners (median outdoor time, high organised PA and sport participation, high screen time, and optimal sleep duration); (3) Poor sleepers (average outdoor time and organised PA and sport participation, low screen time and not meeting sleep guidelines) and (4) Averages (average duration of all behaviours and optimal sleep duration). A major shift in typology membership from 11 to 18 years was observed, with a decreasing proportion of individuals in typologies characterised by a high proportion of outdoor time and participation in organised PA and sport activities (ie, Actives; Active screeners). A high proportion of individuals also transitioned to the typology with poor sleeping habits (ie, Poor sleepers). Sex and maternal education were associated with the typology membership and transition probabilities (p<0.05). CONCLUSIONS: Targeting lifestyle interventions to those with specific lifestyle patterns in early adolescence may be beneficial for reducing the risk of poor sleep and promoting healthy lifestyle patterns later in life.

• Klíčová slova
• Adolescent, Child, PUBLIC HEALTH,
• MeSH
• čas strávený před obrazovkou * MeSH
• chování mladistvých * MeSH
• cvičení * MeSH
• dítě MeSH
• lidé MeSH
• longitudinální studie MeSH
• mladiství MeSH
• prospektivní studie MeSH
• sedavý životní styl MeSH
• spánek * fyziologie   MeSH
• sporty * MeSH
• zdravé chování MeSH
• Check Tag
• dítě MeSH
• lidé MeSH
• mladiství MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• Geografické názvy
• Česká republika MeSH

The distribution of time that people spend in physical activity of various intensities has important health implications. Physical activity (commonly categorised by the intensity into light, moderate and vigorous physical activity), sedentary behaviour and sleep, should not be analysed separately, because they are parts of a time-use composition with a natural constraint of 24 h/day. To find out how are relative reallocations of time between physical activity of various intensities associated with health, herewith we describe compositional scalar-on-function regression and a newly developed compositional functional isotemporal substitution analysis. Physical activity intensity data can be considered as probability density functions, which better reflects the continuous character of their measurement using accelerometers. These probability density functions are characterised by specific properties, such as scale invariance and relative scale, and they are geometrically represented using Bayes spaces with the Hilbert space structure. This makes possible to process them using standard methods of functional data analysis in the L2 space, via centred logratio (clr) transformation. The scalar-on-function regression with clr transformation of the explanatory probability density functions and compositional functional isotemporal substitution analysis were applied to a dataset from a cross-sectional study on adiposity conducted among school-aged children in the Czech Republic. Theoretical reallocations of time to physical activity of higher intensities were found to be associated with larger and more progressive expected decreases in adiposity. We obtained a detailed insight into the dose-response relationship between physical activity intensity and adiposity, which was enabled by using the compositional functional approach.

• Klíčová slova
• Compositional scalar-on-function regression, isotemporal substitution, physical activity, probability density functions, sedentary behaviour, sleep,
• MeSH
• adipozita * MeSH
• Bayesova věta MeSH
• časové faktory MeSH
• cvičení * fyziologie   MeSH
• dítě MeSH
• lidé MeSH
• obezita * MeSH
• průřezové studie MeSH
• Check Tag
• dítě MeSH
• lidé MeSH
• Publikační typ
• časopisecké články MeSH

BACKGROUND: Twenty-four-hour movement behaviours are gaining attention in the research community. However, no study has addressed how 24-h activity profiles vary between structured and less structured days and whether an unfavourable activity profile is associated with childhood obesity. We aimed to analyse differences between school day and weekend day 24-h activity profiles and their associations with adiposity indicators among children and adolescents. METHODS: Participants were 382 children and 338 adolescents who wore wrist accelerometers for 24 hours a day for seven consecutive days. The 24-h activity profile expressed by the average acceleration (AvAcc) and intensity gradient (IG) were estimated from multi-day raw accelerometer data. Adiposity indicators included body mass index (BMI) z-score, fat mass percentage (FM%), fat mass index (FMI), and visceral adipose tissue (VAT). Multiple linear regression of activity profile metrics and adiposity indicators was performed separately for school and weekend days. RESULTS: Weekend days AvAcc and IG were lower compared to school days in both age groups (p <0.001 for all). Specifically, AvAcc was lower by 9.4% and 11.3% in children and adolescents, respectively. IG on weekend days was lower (more negative) by 3.4% in children and 3.1% in adolescents. Among children, on school days AvAcc and IG were negatively associated with FM%, FMI, and VAT, whilst on weekend days AvAcc was positively associated with BMI z-score, FMI, and VAT (p < 0.05 for all). Among adolescents, negative associations were found between weekend day AvAcc and IG and FM% and FMI (p < 0.05 for all), respectively. CONCLUSIONS: This study confirms the importance of 24-h activity profile as a potentially protective factor against excess adiposity. The variability of movement behaviours during structured and less structured days should be considered when optimizing the 24-h movement behaviours to prevent childhood obesity.

• MeSH
• adipozita MeSH
• cvičení MeSH
• dítě MeSH
• index tělesné hmotnosti MeSH
• lidé MeSH
• mladiství MeSH
• obezita dětí a dospívajících * MeSH
• sedavý životní styl MeSH
• Check Tag
• dítě MeSH
• lidé MeSH
• mladiství MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

We examined the compositional associations between the intensity spectrum derived from incremental acceleration intensity bands and the body mass index (BMI) z-score in youth, and investigated the estimated differences in BMI z-score following time reallocations between intensity bands. School-aged youth from 63 schools wore wrist accelerometers, and data of 1453 participants (57.5% girls) were analysed. Nine acceleration intensity bands (range: 0−50 mg to ≥700 mg) were used to generate time-use compositions. Multivariate regression assessed the associations between intensity band compositions and BMI z-scores. Compositional isotemporal substitution estimated the differences in BMI z-score following time reallocations between intensity bands. The ≥700 mg intensity bandwas strongly and inversely associated with BMI z-score (p < 0.001). The estimated differences in BMI z-score when 5 min were reallocated to and from the ≥700 mg band and reallocated equally among the remaining bands were −0.28 and 0.44, respectively (boys), and −0.39 and 1.06, respectively (girls). The time in the ≥700 mg intensity band was significantly associated with BMI z-score, irrespective of sex. When even modest durations of time in this band were reallocated, the asymmetrical estimated differences in BMI z-score were clinically meaningful. The findings highlight the utility of the full physical activity intensity spectrum over a priori-determined absolute intensity cut-point approaches.

• Klíčová slova
• CoDa, accelerometer, adiposity, adolescents, children, intensity spectrum, physical activity,
• MeSH
• cvičení * MeSH
• dítě MeSH
• index tělesné hmotnosti MeSH
• lidé MeSH
• mladiství MeSH
• sedavý životní styl * MeSH
• školy MeSH
• zrychlení MeSH
• Check Tag
• dítě MeSH
• lidé MeSH
• mladiství MeSH
• mužské pohlaví MeSH
• ženské pohlaví MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH