Pattern of Sedentary Behavior in Different Periods of School Time of Brazilian Adolescents

Association of daily and time-segmented physical activity and sedentary behaviour with mental health of school children and adolescents from rural Northeastern Ontario, Canada

Physical activity (PA) and sedentary behaviour (SED) have been linked to the mental health of children and adolescents, yet the timing of behaviours may play a role in this relationship and clarifying this could inform interventions. We explored cross-sectional associations of PA and SED in varying time segments throughout the school day with the mental health of school-aged children and adolescents from rural Northeastern Ontario, Canada. A total of 161 students (56% female, M = 10.3 years old) wore accelerometers for 8 days (7 nights) and completed a self-report survey (parent reported for children younger than 11). Mental health was measured using the Strengths and Difficulties Questionnaire. Accelerometer-measured SED, light PA (LPA), and moderate and vigorous PA (MVPA) were estimated in the time-segments before school (06:00–08:44), school time (08:45–15:04), after school (15:05–16:59), and evenings (17:00–21:59). Associations were tested with multilevel linear regressions while adjusting for confounding factors. Students spent 72.6 min in MVPA, 209.0 min in LPA, and 621.0 min in SED per day. Daily SED was associated with less conduct problems (β = −0.27, p < 0.05). Evening LPA was inversely associated with hyperactivity (β = −1.45, p < 0.05), while SED was associated with hyperactivity and with peer problems before school (β = 1.70 and β = 1.01, respectively, p < 0.05), and during school (β = −0.83 and β = −0.57, respectively, p < 0.05). No associations were observed for MVPA, emotional symptoms, or prosocial behaviour. In conclusion, displacing SED with LPA in some specific periods of the day may benefit the mental health of students; taking this into account could strengthen interventions.

Relationship of Objectively Measured Physical Activity, Sedentary Behavior and Sleep Time with Cardiovascular and Mtabolic Outcomes in Adolescents (A Pilot Study): ABCD Growth Study

STUDY OBJECTIVE

Different behaviors are considered important factors that may influence a healthy lifestyle. Given this fact, we aim to analyze the relationship between moderate-vigorous physical activity (MVPA), sleep time, and sedentary time, with cardiometabolic outcomes in adolescents.

METHODS

Cross-sectional study, with 152 eutrophic and healthy adolescents. The behavioral variables were collected objectively and the arterial thickness was measured through ultrasound. Blood variables (LDL, TG, HDL, glucose, and insulin) were collected in a private laboratory. To analyze the data, the Student t test and Kruskal-Wallis test were used to compare the groups. All analyses adopted p < 0.05.

RESULTS

Girls who demonstrated better combined behaviors, presented significant results for TG (p = 0.045), BP (p = 0.016), and cardiovascular score (p = 0.049) when compared to their peers. Furthermore, the practice of physical activity combined with sufficient sleep time was associated with lower values of arterial thickening (p = 0.017).

CONCLUSIONS

In view of the results presented, it is possible to state that the aggregation of behaviors was more consistent in females and that the practice of physical activity and adequate sleep time can reflect on cardiovascular health.

Accelerometer-measured physical activity and sedentary behavior in Chinese children and adolescents: a systematic review and meta-analysis

OBJECTIVE

To synthesize evidence on accelerometer-measured moderate-to-vigorous physical activity (MVPA) and sedentary behavior (SB) levels of Chinese children and adolescents.

STUDY DESIGN

This is both a systematic review and meta-analysis study.

METHODS

Online databases were searched for studies published from January 2009 up to February 2019. These studies reported accelerometer-measured daily minutes of MVPA and/or SB among Chinese children and adolescents. Random-effects meta-analysis was used to separately pool the time spent in MVPA and SB.

RESULTS

Of 4754 records, 20 studies were included in the meta-analysis. Sample sizes ranged from 96 to 2163. The meta-analysis showed that Chinese children and adolescents spent 41.11 min/day in MVPA and 529.83 min/day in SB averagely. Boys spent more time in MVPA compared with girls (P = 0.01). Children accumulated more MVPA time than adolescents (P = 0.05), and children spent less time in SB than adolescents (P = 0.05). Unlike weekdays, SB was lower on weekends (P = 0.02). There were significant differences in children and adolescents' MVPA time in regions (P < 0.001).

CONCLUSIONS

MVPA level in Chinese children and adolescents is well below international recommendations, and their SB level is very high.

Changes in the school and non-school sedentary time in youth: The UP&DOWN longitudinal study

The aims of this study were (i) to examine the sedentary time (ST) during different time periods [i.e., weekend, out-of-school weekdays hours, school hours, recess, physical education classes (PEC)] in children and adolescents; (ii) to identify 2-year longitudinal changes in the ST for these periods; and (iii) to examine if ST at baseline is associated with ST 2 years later. This was a 2-year follow-up study with 826 (51.9% boys) children and 678 (50.7% boys) adolescents. Accelerometers were used to assess ST. Students spent more than 60% of their weekend, out-of-school hours and school hours in ST. During these periods, girls and adolescents were more sedentary than boys and children, respectively (p < 0.05). Over 2-year follow-up, ST increased during the weekend, out-of-school hours, school hours and recess in all subgroups studied (p < 0.001). ST during PEC declined 2% per year in children (p < 0.001) but it increased in adolescents (p < 0.05). ST during the periods analysed at baseline was lowly associated with ST during these periods 2 years later (intraclass correlations from <0.001 to 0.364). Interventions in these settings may be adequate if the intention is to avoid ST increase in students.