fidelity to the treatment.
These simple interventions, which could be adopted in every primary school, have the potential of initiating a self-sustaining cycle of prevention for childhood obesity, bullying and mental ill health.
Australian and New Zealand Clinical Trials Registration Number ACTRN12611000089932.
Disturbing numbers of children in the westernised world are overweight, bullied or have poor mental health. These are all serious childhood problems that are notoriously difficult to treat. Prevention is undoubtedly best, but their continued increase shows how difficult it is to reverse these new and dangerous trends. Burdette and Whitaker  suggested a compelling common cause for all three problems: a decrease in outdoor free play. While previous generations spent most of their discretionary time engaged in free play outdoors, today's children play indoors; their free time is often spent in sedentary and solitary activity (e.g., computers, television). Time spent outdoors is often in structured sport rather than in unstructured play that facilitates social interaction and physical activity. Physical activity promotes energy expenditure and has additional benefits such as improved cardiovascular health and gross motor skills. However, less obvious is the role of free play in children's social, emotional and cognitive development. The shift from outdoor play to indoor activities, combined with an increased push for academic achievements, potentially leave children more stressed and with poorer mental health . Most young children love active outdoor play but parents, teachers and carers may limit this, fearing injury or misadventure.
Risk aversion in the short term can lead to greater risks in the long term
Adult fears are often disproportionate to actual risk: while children can be injured when playing outdoors, most are minor cuts and bruises. On the other hand, restricting children's outdoor play activities may have unintended consequences, such as reducing children's opportunities for reasonable, age-appropriate risk-taking. Fear of litigation results in minimising "risk" at all cost and decreasing the value of "real play" that occurs on school playgrounds [2, 3]. Several schools have now placed a ban on running on the school playground [4, 5]. Thus, "surplus safety" may result in exactly the negative outcomes it was meant to avert . Although no research has directly examined risk avoidance and children's health outcomes, recent Australian data suggest that concern with children's risk exposure can lead to constraints on children's habitual physical activity, which may have negative public health outcomes . Further, when children perceive that play settings are not demanding enough, they may compensate by engaging in activities that yield challenges -- in the context of undesirable behaviour (e.g., bullying or using play equipment in truly dangerous ways).
Social and Physical Environments Affect Play
Opportunities to engage in spontaneous play in the local neighbourhood have declined in recent generations . The age at which children are allowed outside to play on their own has increased in recent years . While parents of older children may have greater tolerance for allowing their children to take manageable risks, young children are generally not allowed to engage in what parents perceive as risky play or activities. Mullins and colleagues  speculated that parents are less likely to engage in overt overprotective behaviours as their children reach adolescence, yet still perceive their child as vulnerable. Children are often driven by car to play activities  and these activities are likely to be adult-organised and indoors . When children are allowed to play outside, it is often on the school playground for which rules limit play behaviours  and purpose-built equipment (e.g., slide) fails to promote collaborative and imaginative play. Slides and climbers are also the source of most serious playground injuries  and climbers are often places in which less physically competent children are teased by peers .
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