Dalene KE, et al. - Researchers included nationally representative samples of Norwegian 9- and 15-y-olds in this study to determine how sleep, screen time, active school travel and sport and/or exercise participation relates to moderate-to-vigorous physical activity (MVPA) in these subjects. They also determined if change in MVPA from age nine to 15 years could be predicted by these four behaviors at age nine. Data were pooled for the participants of the Physical Activity among Norwegian Children Study to investigate cross-sectional links. A sub-sample was also examined to determine prospective links. Findings revealed no cross-sectional link between sleep duration and MVPA in either age group. Change in MVPA from age nine to 15 years was not predicted by any of the four behaviors. Overall, for increasing MVPA in children and adolescents, the possible importance of active travel to school and sport/exercise participation was suggested as targets for future interventions.