AbstractPhysical activity (PA) and sedentary behaviour (SED) have been linked to the mental health of children, yet, the timing of behaviours may play a role in this relationship and clarifying this role could inform interventions. We explored the associations of PA and SED in different time segments of the school day with the mental health of children from Northeastern Ontario. 161 students (56% female, M = 10.2 years old) wore GENEActiv accelerometers for 7 days and completed a self-report survey (parent-reported for younger children). Mental health was measured using the Strengths and Difficulties Questionnaire. 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. Students spent, on average, 73 minutes in MVPA, 290 in LPA, and 621 in SED per day. Overall SED was associated with conduct problems (?=-0.27). LPA on evenings was associated with hyperactivity (?=-1.45), while SED before school was associated with hyperactivity and peer problems (?=1.70 and ?=1.01, respectively), and during school (?=-0.83 and ?=-0.57, respectively). No significant associations were observed for PA and SED with emotional symptoms or prosocial behaviour, and MVPA was not significantly related to any mental health indicator. Displacing SED with LPA may be beneficial for children's mental health in some but not in other periods of the day. Future studies should explore qualitative aspects of PA and SED contexts that could explain the link with mental health.
Acknowledgments: This study is supported by the Canadian Institutes of Health Research (PJT-156209).