Background The present cross-sectional study aimed to determine the proportion of adolescents meeting the 24-hour movement guidelines, and investigate sociodemographic factors associated with meeting them. Methods Self-reported (average daily volume of MVPA, sleep duration, and time watching videos and playing videogames) and accelerometer-measured (MVPA and sleep duration) 24-hour movement behaviors were classified according to recommendations, and sex, age, socioeconomic status (SES), family structure, parental education, and number of people in the household were tested as correlates of meeting recommendations using multilevel logistic regressions. Results The proportion of adolescents (n = 867, mean age: 16.4 years, 50.3% girls) meeting the MVPA, ST, and sleep duration guidelines was of 25%, 28%, and 41%, respectively, for selfreported data. From accelerometer data (n = 688), 7.1% met MVPA and 31.7% met sleep duration recommendations. Adherence to all three recommendations was 3% with selfreport and 0.2% with accelerometer data. Boys were more likely to meet MVPA, but not ST and sleep-duration recommendations. A positive relationship was observed between age and meeting the ST recommendation. Conclusions Adherence to the sleep duration recommendation was higher than to the screen-time and MVPA recommendations and few in this sample of Brazilian adolescents achieved the 24-hour guidelines. Efforts are needed to improve 24-hour movement behaviors.

This study aimed to analyze the association between lifestyle behaviors and health-related quality of life (HRQoL) among Brazilian adolescents. We evaluated 739 adolescents (51.0% girls; mean age, 16.4 ± 1.0 years) from the mesoregion Grande Florianópolis, Brazil. Participants were asked to complete an online questionnaire and sex, age, mother’s education, health-related quality of life, physical activity, screen time indicators, sleep duration, diet, cigarette smoking, alcohol drinking, and drug experimentation were retrieved. Health-related quality of life was assessed using the Kidscreen-10 instrument. Measures of body mass and height were taken by trained researchers. Mixed-effects linear regression models were used. Self-reported health-related quality of life was higher in males (β = 3.68, 95%CI: 2.75; 4.61) compared to females, and no association was observed for age and mother’s education level. Practicing sports (β = 1.19, 95%CI: 0.29; 2.08) was associated with better HRQoL, while processed food score (β = −0.45, 95%CI: −0.78; −0.13), working using screen devices for more than 4 h/day (β = −2.38, 95%CI: −4.52; −0.25), having experimented illicit drugs (β = −2.05, 95%CI: −3.20; −0.90), and sleeping less than 8 h/night (β = −1.35, 95%CI: −2.27; −0.43) were unfavorably associated with HRQoL. Non-sport physical activities, unprocessed food, studying, watching videos, playing videogames, using social media, alcohol drinking, and smoking were not associated with health-related quality of life. These findings suggest that promoting sports and adequate sleep, and preventing excessive workloads and the use of drugs among adolescents may be effective strategies to improve HRQoL.

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The aim of this study was to summarize studies examining the prevalence of sedentary behavior among Brazilian children and adolescents. A systematic review conducted on eight databases (PubMed, Scopus, Web of Science, LILACS, SPORTDiscus, BIREME, Scielo, and Google Scholar). The criteria applied were: original research; samples including Brazilian children and adolescents; to be a school- or population-based survey; observational studies using different measures of sedentary behavior; studies showing the prevalence of at least one component of sedentary behavior. Of the 205 studies included, 104 were analyzed. There was a greater concentration of studies in the southern (n=41) and northeastern (n=18) regions. The components more frequently investigated were watching TV (n=36) and screen time (n=32). Only three studies included children under seven years, and the age range more investigated was 10 to 19 years. Most of the studies used a self-reported questionnaire and showed variability in the cut-off point applied (from 2 to 4 hours/day). The prevalence of adolescents who met recommendations ranged from 9.4% to 68.0% for sedentary behavior (<2 hours/day) and from 16.8% to 67.2% for TV viewing (<2 hours/day). The prevalence ranged from 39.1% to 97.7% for computer use and from 47.7% to 98.0% for videogame use. Most of the studies reported that less than half of the adolescents met the recommendations of sedentary behavior and TV viewing. On the other hand, more than half of them devoted less than two hours a day to computer and videogame use.

This study analysed physical activity (PA) and sedentary behaviour (SB) performed in bouts during schooltime. Adolescents of two schools answered a questionnaire, had their height and weight measured and wore accelerometers during schooltime. Moderate-to-vigorous intensity PA was estimated in bouts of 2, 5 and 10 min, and SB in bouts of 5, 10, 30 and 60 min. Body mass index was calculated, and adolescents were classified as overweight or normal weight. Frequency, duration and volume of PA and SB were calculated for the whole sample and for those who performed at least one bout weekly. PA and SB differences between gender and weight status were tested using Mann-Whitney and t tests. A total of 415 adolescents (54% girls, 12.3 ± 1.3 years old, 34.6% overweight) performed 0.1 (± 0.2), 0.2 (± 0.5) and 0.4 (± 0.6) bouts of 10, 5 and 2 min of PA, and 10.6 (± 2.0), 6.0 (± 1.3), 1.1 (± 0.9) and 0.4 (± 0.5) bouts/day of 5, 10, 30 and 60 min of SB, respectively. Boys accumulated less SB and more PA in bouts. No differences were found for weight status.Conclusion: Adolescents hardly engaged in bouted PA and accumulated more SB in smaller bouts during schooltime. Bouted PA and SB were not associated with weight status. What is Known: • Adolescents are not engaging in enough PA and are accumulating large volumes of SB, which might negatively impact their health. • Schools play an important role in daily overall PA, with opportunities such as PE classes and recesses. But most classes are still undertaken in seated positions. What is New: • Adolescents hardly engage in bouted (> 10 m) PA when at school., and most SB is accumulated in short bouts (≤  10m). • Weight status was not associated with bouted PA or SB at school.