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 .
Preschool Physical Activity and Functional Constipation: The Generation R Study
Objectives : Decreased physical activity levels in children may partly explain the rising prevalence of  functional constipation in childhood . The aim of the present study , therefore , was to examine the association between physical activity  and functional constipation during the preschool period . Methods : This study was embedded in the Generation R study , a large prospect i ve birth-cohort study in Rotterdam , The Netherl and s. Physical activity was measured by an Actigraph accelerometer in 347 children ( 182 boys , 165 girls ; mean age 25.1 months ) and data were expressed as counts per minute . Data were categorized into light activity ( 302–614 counts/15 seconds ) , moderate activity ( 615–1230 counts/15 seconds ) , and vigorous activity ( ≥1231 counts/15 seconds ) . Functional constipation in the third and fourth year of life was defined according to the Rome II criteria . Results : Children spending time in the highest tertile of light ( adjusted odds ratio [ OR ] 0.34 ; 95 % confidence interval [ CI ] 0.13–0.87 ) , moderate ( adjusted OR 0.37 ; 95 % CI 0.14–0.97 ) , and total activity ( adjusted OR 0.37 ; 95 % CI 0.15–0.92 ) at the age of 2 years had significantly less functional constipation in the fourth year of life . For functional constipation in the third year of life , the results were in similar direction but not statistically significant . Additionally , children with physical activity of more than the WHO recommendation of 60 min/day had significantly less functional constipation in the fourth year of life ( adjusted OR 0.48 ; 95 % CI 0.24–0.97 ) . Conclusions : Physical activity is associated with a decreased risk of functional constipation  in the preschool period , but this may be time dependent
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 .