PA correlates/determinants were relatively consistent between objective and subjective PA measures .
A small number of demographic/biological and social/cultural factors were associated with PA .
CONTEXT Being physically active during the early years ( age 0 - 6 years ) is vital for healthy development .
Identifying correlates and determinants of physical activity ( PA ) is crucial to guide effective interventions .
This systematic review synthesized studies investigating potential correlates and determinants of PA during the early years , accounting for different types of PA assessment .
Effect of a school-based active play intervention on sedentary time and physical activity in preschool children.
Early childhood is a critical time for promoting physical activity . Few studies have investigated the effect of interventions in this population . The aim of this study was to investigate the effect of a school-based active play intervention on preschool children 's sedentary time and physical activity .  Preschool children were recruited from r and omly selected preschools . Schools were r and omly assigned to an intervention or comparison group . One teacher per intervention school received training from active play professionals in the delivery of a 6-week active play programme . Comparison schools continued their usual practice . Children wore a  uni-axial accelerometer  for 7 days at baseline , immediately after and at 6-month post-intervention . No significant intervention effects were observed for sedentary time or physical activity . However , sex and hours spent at school were significant predictors of physical activity . Children who spent fewer hours ( half-day children ) at school were significantly more active than their full-day counterparts . Physical activity during the intervention classes was high even though neither daily physical activity nor sedentary time changed . Notably children who spent more time at preschool were less active suggesting that preschool was not as conducive to physical activity engagement as other environments
PA correlates/determinants were relatively consistent between objective and subjective PA measures .
A small number of demographic/biological and social/cultural factors were associated with PA .
CONTEXT Being physically active during the early years ( age 0 - 6 years ) is vital for healthy development .
Identifying correlates and determinants of physical activity ( PA ) is crucial to guide effective interventions .
This systematic review synthesized studies investigating potential correlates and determinants of PA during the early years , accounting for different types of PA assessment .