Postgraduate Program in Epidemiology, Federal University of Pelotas, Pelotas, Brazil.
Public Health Nutr. 2012 Dec;15(12):2237-45. doi: 10.1017/S1368980012000948. Epub 2012 Mar 30.
To investigate the predictors of change in physical activity (PA) from early to mid adolescence in a cohort of adolescents.
Prospective, population-based birth cohort study. PA level was evaluated by means of questionnaire, and was analysed in continuous form (min/week) and as a trajectory (inactive-inactive, inactive-active, active-inactive, active-active) based on the cut-off point of 300 min/week.
Pelotas, a city of 340 000 inhabitants in southern Brazil.
Adolescents (n 4120) followed from 11 to 15 years of age.
Maternal PA change and more exposure to outdoors were directly associated with a positive change in PA level (min/week) for both genders. Higher maturation status (among boys) and later menarche were also associated with positive PA change in min/week. Predictors to remain inactive were: maternal PA change (inverse association), more exposure to outdoors, higher socio-economic level, fear of living in the neighbourhood and non-overweight girls. Predictors to become inactive were higher socio-economic level among boys and increase in screen time among girls.
The study demonstrates that social, family, biological, behavioural and environmental factors exert an important role in the PA change among youngsters as they move into adolescence. These findings may be relevant to the design of policies and intervention programmes aimed at promoting PA in teenagers.
在青少年队列中研究从青春期早期到中期身体活动（PA）变化的预测因素。
前瞻性、基于人群的出生队列研究。通过问卷评估 PA 水平，并以连续形式（分钟/周）和轨迹（不活动-不活动、不活动-活动、活动-不活动、活动-活动）进行分析，基于 300 分钟/周的截止值。
巴西南部拥有 34 万居民的佩洛塔斯市。
从 11 岁到 15 岁的青少年（n=4120）。
母亲 PA 变化和更多的户外活动与两性 PA 水平（分钟/周）的积极变化直接相关。较高的成熟状态（男孩）和较晚的初潮也与每周 PA 的积极变化有关。保持不活动的预测因素包括：母亲 PA 变化（负相关）、更多的户外活动、更高的社会经济水平、对邻里生活的恐惧和非超重女孩。成为不活跃的预测因素是男孩的社会经济水平较高，女孩的屏幕时间增加。
该研究表明，社会、家庭、生物、行为和环境因素在青少年进入青春期时对 PA 变化起着重要作用。这些发现可能与设计旨在促进青少年 PA 的政策和干预计划有关。
