Stability and bidirectional relationship between physical activity and sedentary behaviours in Brazilian adolescents: Longitudinal findings from a school cohort study.

PURPOSE: We investigated the stability, correlations and bidirectional relationship of light physical activities (PA), moderate and vigorous PA (MVPA), television viewing (TV) and video game/computer use (VG) in Brazilian adolescents.

METHODS: Adolescent Nutritional Assessment Longitudinal Study-ELANA is a middle school cohort study conducted in Rio de Janeiro-Brazil in 2010-2012. Self-reported data on PA (International Physical Activity Questionnaire- IPAQ) and screen activities were obtained from 810 adolescents (mean ages of 10.9 years old (SD 0.78) for girls; 11 years old (SD 0.85) for boys) to perform autoregressive cross-lagged structural equation models in two time points for PA and three time points for screen activities.

RESULTS: There was no significant stability of light PA and MVPA for boys and girls. Moderate stability of screen activities were found for both genders, with a significant coefficient of TV for boys (T1-T2:0.29; T2-T3:0.27 p<0.001); and VG for boys (T1-T2:0.33; T2-T3:0.35 p<0.001) and girls (T1-T2: 0.26; T2-T3:0.37 p<0.01). Significant lagged effects were obtained only among girls: light PA had effect on VG (-0.10 p<0.01), as well as in the opposite direction of TV on light PA (-0.03 p<0.01) and TV on MVPA (-0.11 p<0.01).

CONCLUSION: The light PA, MVPA and screen activities (among girls) did not demonstrate stability over time. A warning scenario was suggested by the stability of high amounts of screen activities among boys over time. Screen activities had bidirectional association with light PA and MVPA among girls over time.