Longitudinal relationship between organised and non-organised physical activities and overall physical activity in children aged 3-11 years.

Young children's physical activity (PA) has been decreasing while their sports participation has been increasing. Therefore, the aim of this research was to longitudinally examine whether and, if so, how organised and non-organised PA participation by early childhood education and care (ECEC)-aged children (T1; 3-8 years) predicted their accelerometer-measured PA at primary school age (T2; 7-11 years). Secondarily, changes in organised and non-organised PA participation over time were investigated. The cluster-randomised study participants comprised 501 Finnish children (52.3% girls: T1, M = 5.57 ± 1.06; T2, M = 8.80 ± 1.07). PA participation was queried via guardian questionnaire at T1 and T2. Organised PA participation was operationalised as non-participation, participation in one sport or multisport (two or more) participation; non-organised PA was operationalised as time spent outdoors on weekdays and on weekend days. PA at T2 was measured using accelerometers. The primary outcome was tested using linear regressions, while a paired sample t-test and Mann-Whitney U test assessed differences between T1 and T2. The results showed outdoor time and organised sports participation increased from T1 to T2. Moreover, outdoor time at T1 predicted more moderate-to-vigorous PA (MVPA) and less sedentary time at T2, while multisport participation predicted significantly more MVPA and less sedentary time at T2. Overall, being outdoors and multisport participation at younger ages appear to have predicted Finnish children's later (MV) PA and sedentary behaviour.