Physical inactivity is a risk factor for physical activity-related injuries in children.

OBJECTIVES: To describe the risk factors associated with injuries resulting from physical education (PE), leisure time physical activity (leisure time PA) and sports in 9-12-year-old children. DESIGN: Prospective cohort study. SETTING: Primary schools. PARTICIPANTS: Nine hundred and ninety-five children aged 9-12 years. MAIN OUTCOME MEASURES: Injuries occurring during either PE class, leisure time PA or sports, and caused the child to at least stop the current activity were recorded prospectively. Individual weekly exposure was estimated from baseline and follow-up questionnaires. Potential risk factors were gender, age, socioeconomic status, ethnicity, habitual level of PA, body mass index and a motor fitness. A multivariate Cox proportional hazard regression model was developed, accounting for clustering within schools. RESULTS: Gender, age and level of PA were independent significant risk factors for injury. Different modalities of PA had different injury risk factors. Most importantly, the low levels of habitual PA significantly increased injury risk. CONCLUSIONS: The children at highest injury risk are the target audience of the contemporary PA promotion efforts. PA promotion should also focus on injury prevention.

A cluster-randomized controlled trial to reduce sedentary behavior and promote physical activity and health of 8-9 year olds: the Transform-Us! study.

BACKGROUND: Physical activity (PA) is associated with positive cardio-metabolic health and emerging evidence suggests sedentary behavior (SB) may be detrimental to children's health independent of PA. The primary aim of the Transform-Us! study is to determine whether an 18-month, behavioral and environmental intervention in the school and family settings results in higher levels of PA and lower rates of SB among 8-9 year old children compared with usual practice (post-intervention and 12-months follow-up). The secondary aims are to determine the independent and combined effects of PA and SB on children's cardio-metabolic health risk factors; identify the factors that mediate the success of the intervention; and determine whether the intervention is cost-effective. METHODS/DESIGN: A four-arm cluster-randomized controlled trial (RCT) with a 2 × 2 factorial design, with schools as the unit of randomization. Twenty schools will be allocated to one of four intervention groups, sedentary behavior (SB-I), physical activity (PA-I), combined SB and PA (SB+PA-I) or current practice control (C), which will be evaluated among approximately 600 children aged 8-9 years in school year 3 living in Melbourne, Australia. All children in year 3 at intervention schools in 2010 (8-9 years) will receive the intervention over an 18-month period with a maintenance 'booster' delivered in 2012 and children at all schools will be invited to participate in the evaluation assessments. To maximize the sample and to capture new students arriving at intervention and control schools, recruitment will be on-going up to the post-intervention time point. Primary outcomes are time spent sitting and in PA assessed via accelerometers and inclinometers and survey. DISCUSSION: To our knowledge, Transform-Us! is the first RCT to examine the effectiveness of intervention strategies for reducing children's overall sedentary time, promoting PA and optimizing health outcomes. The integration of consistent strategies and messages to children from teachers and parents in both school and family settings is a critical component of this study, and if shown to be effective, may have a significant impact on educational policies as well as on pedagogical and parenting practices. TRIAL REGISTRATION: ACTRN12609000715279; Current Controlled Trials ISRCTN83725066.