Abstract
BACKGROUND: Physical activity (PA) participation among youth tends to be insufficient and is prone to decline with age. In Australia, this decline has been shown to particularly occur in the domain of non-organized PA (e.g. active play and informal sport) between childhood and adolescence. However, information about changes in more specific groupings of activities within non-organized PA (i.e. subdomains) is needed, as this could support more targeted intervention strategies. This study aimed to investigate changes in the duration of specific subdomains of non-organized PA between late childhood (10-11 years) and early adolescence (12-13 years) in Australia, as well as whether these changes are moderated by sex. METHODS: Data were sourced from Waves 6 and 7 of the Longitudinal Study of Australian Children (n = 3614). Youth time-use diaries (24-h) were used to measure the duration of eight subdomains of non-organized PA at both waves (athletics/gymnastics, ball sports, cycling/motor/roller sports, fitness/gym/exercise, martial arts/dancing, water/ice/snow sports, active play and other outdoor/nature PA). Multilevel mixed modelling was used to explore longitudinal changes between waves and the potential moderation effect of sex. RESULTS: Active play declined the most of all subdomains (β = -20.5 min/day; 95% CI = -23.4, -17.6, p < 0.001). A smaller decline was observed in the subdomain of non-organized ball sports (β = -4.1 min/day; 95% CI = -5.9, -2.3, p < 0.001). Other subdomains remained stable or had only very small changes in participation. The decline in active play was moderated by sex, with a steeper decline among girls. No other notable moderation effects were observed. CONCLUSIONS: Future studies may seek to explore and test the acceptability of PA promotion strategies to encourage active play participation, such as 'reframing' childhood play activities to be appropriate for adolescents. Such studies might particularly seek the perspectives of girls in the transition to adolescence.