Escalating levels of obesity and chronic disease worldwide1^–3 have ignited public health interest in physical activity and inactivity.3 There is a large body of evidence to suggest that physical activity contributes significantly to the health of the cardiovascular, cellular, endocrine and skeletal systems and to mental health.4 On the flip side, the human and economic costs of physical inactivity are profound. In England physical inactivity costs taxpayers an estimated £8.2 billion a year.5 This staggering sum includes direct costs of treatment for the major lifestyle-related diseases and the indirect costs caused through sickness absence. In Australia, physical inactivity among adults costs the healthcare system $A1.5 billion a year.6 Similar costs in Canada are $C5.3 billion ($C1.6 billion in direct costs and $C3.7 billion in indirect costs).7 These global costs are avoidable.

Prevention must begin at a young age. The new reality in developed countries is the presence of chronic disease risk factors in young children and adolescents.8 9 Furthermore, health behaviours track across phases of life,10^–13 cluster together,14 and adults have substantial difficulty adopting and adhering to healthy behaviours.15 16 It thus seems prudent to invest our resources in encouraging physical activity during the growing years and to sustain these efforts throughout life.

There has been a recent shift to an ecological approach to address the challenge of child and youth physical inactivity.17 This approach acknowledges that an individual’s behaviour has an influence on, and is a consequence of, the context and settings in which they live, learn, work and play.18^–20 Public health professionals21 and physical activity researchers22 23 have identified the school as a critical setting for action.

We provide a synopsis of literature that addresses the promotion of physical activity in schools and highlight emerging models and approaches. Finally, we discuss the implications of these models for public health professionals who seek to adopt a more ecological approach, who integrate their work with patients (children and families) with that of the broader community, and who advocate that programmes be evidence based.

ARE SCHOOLS THE APPROPRIATE SETTING FOR PHYSICAL ACTIVITY INTERVENTIONS?

Schools have long been recognised as potentially effective settings for public health initiatives,21 as they access a large population of children and youth across broad ethnic and socioeconomic strata.24 Furthermore, children and adolescents spend approximately half of their waking hours in school during the school year,25 for between 6 and 12 years of their lives.21 This creates an extended window of opportunity to promote physical activity for all children, regardless of their life circumstances. Schools often play a formal role in delivering health and physical education (PE), thus potentially influencing knowledge and attitudes towards health habits as well as making a unique contribution to total daily physical activity.26^–28 However, schools are complex, busy places where the core business is learning.21 Not surprisingly, common barriers to implementing school-based physical activity models include insufficient time, competing priorities, lack of resources and non-supportive environments.29^–31 One of the key challenges for public health and education professionals will be to facilitate and sustain the widescale uptake and implementation of any physical activity model effectively, even those with demonstrable health benefits for children.31 32

ARE SCHOOL-BASED INTERVENTIONS EFFECTIVE?

The past decade boasts a proliferation of studies and several systematic reviews that addressed whether school-based interventions were an effective means to promote physical activity in children (primary or elementary schools) and youth (middle or secondary schools).33^–39 It is important to acknowledge a number of key issues at the outset. First, the structure of elementary and high schools and the students who reside within them are distinctly different. Elementary schools are typically organised around generalist teachers, whereas secondary schools are organised around subject specialists,37 39 are often divided by grade levels (junior and senior) and may operate on a semester system. High school marks the transition to young adulthood, and adolescence is characterised by a shift to independent decision-making that is strongly influenced by peers, technology and the mass media.39 In many jurisdictions, high school PE may be optional. Therefore, one size does not fit all. School-based physical activity models that serve one school or age group may not be appropriate for another.

Second, measurement tools must also be age appropriate and self-report instruments in particular are problematical for younger age groups.40 Indeed, lack of precise measures of physical activity may well affect the outcome of paediatric studies.35 41 Objective measures of physical activity (direct observation, pedometers and accelerometers)34 35 are emerging as the accepted gold standard. In their recent systematic review of children’s physical activity literature, van Sluijs et al35 noted that 55% of studies relied upon self or parent reports of physical activity. Specifically within schools, more than three-quarters of the educational interventions and almost half of multicomponent interventions reviewed used self report.

Third, regardless of the model, school-based approaches to increasing physical activity present an evaluation challenge. Schools are hierarchical clusters; classes are clustered within schools and children are clustered within classes. “Nesting” must be managed within the research design or the statistical approach to data. Finally, in-school models demand that all children be invited to participate when 60% of children may already be undertaking sufficient daily physical activity—this may create a ceiling effect and serve to dilute the effect of the intervention. We thus summarise the evidence within both the elementary and secondary school context and with these measurement limitations in mind.

In a recent systematic review of interventions to promote physical activity for both children and youth, 82% and 83% of studies of children and adolescents, respectively, were school-based interventions.35 Physical activity levels of children and youth were enhanced either modestly (2.6 minutes of moderate vigorous physical activity (MVPA) during PE) or substantially (83 minutes of MVPA per week; 42% increase in regular physical activity per week) depending on the study design and type of intervention. We highlight the intervention approaches and conclusions drawn from this and other systematic reviews33^–35 37 38 and introduce more recent and promising contributions to the literature below.

WHAT TYPE OF STRATEGY WITHIN SCHOOLS IS MOST EFFECTIVE?

Generally, interventions reviewed in the literature fall into three main categories: educational, environmental and multicomponent or comprehensive “whole school” approaches.35

Educational strategies focus on changing knowledge, attitudes and motivation and are typically classroom based. Education-only interventions did not enhance physical activity in either the elementary or secondary school setting.34 37 42 One exception is classroom-based interventions that targeted screen time and incorporated self-assessment and tracking; these interventions significantly reduced sedentary behaviour.43^–45 Classroom-based health education increased knowledge and positively affected psychosocial variables in some studies.46 These psychosocial adaptations may be part of, but probably not all, that is necessary to change and maintain physical activity over the life course.

Environmental strategies change the physical environment, policies or practices within the school to provide more physical activity opportunities. These approaches varied, but their defining feature was the absence of a curriculum or pedagogical component that targeted knowledge and psychosocial factors. Studies that utilised environmental strategies only (not including PE studies) demonstrated a consistent positive effect.35 However, there are relatively few of them, particularly at the high school level. At the elementary level evidence supports changing playground markings and providing more equipment to encourage play in school breaks.35 However, there is insufficient evidence for these types of approaches with youth.23 35 46 Furthermore, categorising interventions for review has posed a problem; PE-based strategies have been viewed as educational versus environmental35 and many environmental interventions were incorporated within multicomponent approaches. It thus becomes difficult to identify the specific contribution of the various components of the intervention. The Middle School Physical Activity and Nutrition Trial is notable for its high quality and level of evidence. The Middle School Physical Activity and Nutrition Trial demonstrated the effectiveness of an environmental approach47 through increased physical activity in the PE class, facilitated physical activity in school breaks, increased PE and physical activity equipment (with funding) and the provision of mass communication/media information about physical activity. Student health committees planned monthly activities and held health policy meetings to select and implement policy changes.

A relatively novel and effective environmental approach has been to incorporate activity breaks into the elementary school classroom. As these studies are newly completed many of them were not included in the most recent systematic reviews. Take 10,48 Physical Activity Across the Curriculum,30 Energizers,49 Promoting Lifestyle Activity for Youth50 and Jump In51 teachers provided additional minutes of physical activity in class throughout the school day. “Classroom Action” was also the foundation piece of the Action Schools! BC intervention, although the model specified that physical activity also be promoted across five other zones—PE, extracurricular, school spirit, family and community and the school environment. Action Schools! BC showed a positive effect on physical activity,52 cardiovascular8 and bone health,53 54 and children in intervention schools performed at least as well academically with fewer curricular minutes as children in control schools.55 With the exception of Jump-In, all studies used either pedometers or accelerometers to measure physical activity. Increases in physical activity although statistically significant were modest (eg, 1000–1500 steps in the pedometer studies) and in some cases significance was achieved only for specific subgroups.51 52 Regardless of this, this simple and feasible approach holds promise as the response was consistent across similar interventions and was closely related to the reported physical activity “dose”.

Within elementary, middle and high schools there is also mounting evidence that PE-based strategies are effective for increasing physical activity37 38 and the Child and Adolescent Trial for Cardiovascular Health (CATCH) demonstrated that changes can be maintained over time.56 Effective PE-based approaches included: more frequent PE (eg, four times per week);57 more MVPA during PE classes38 57^–59 and PE delivered by PE specialists or trained generalist teachers compared with generalist teachers without specific training.60 61 Fairclough and Stratton37 cautioned that although PE contributes to overall physical activity it should not be viewed as a panacea. The duration and frequency of PE lessons are restricted in many jurisdictions and the PE curriculum is designed to address a diverse range of activities and educational goals—not solely physical activity. PE should thus be considered a natural opportunity to promote physical activity that complements but does not replace other initiatives within the school.37

Importantly, many of the modifications to the school environment that promote physical activity practice and policy could potentially be incorporated and sustained on a population level.

Multicomponent strategies combine a number of entry points across settings within the school (eg, classroom, family, PE, playground, etc). These strategies often incorporated physical activity within a broader chronic disease or obesity prevention approach. For instance, early multicomponent strategies such as CATCH targeted MVPA delivered in PE specifically.62 More recent “active school” models addressed PE but also promoted physical activity via different approaches and settings within the school (eg, classroom, school events, recess, etc). There is as yet only sparse evidence that this approach works at the elementary school level. However, the increased physical activity in intervention children participating in Action Schools! BC,52 Physical Activity Across the Curriculum30 and Jump-In,51 is promising.

There is strong evidence to support multicomponent strategies for youth.35 The Lifestyle Education for Activity Program is a multicomponent initiative that significantly enhanced vigorous physical activity in girls.63 Core components within the Lifestyle Education for Activity Program were: modified PE instruction and health education to enhance self-efficacy and enjoyment and environmental changes (required: principal support, communication messages and a school physical activity planning team; optional: staff health promotion, family and community involvement).

There was also strong evidence to support incorporating family and community components, especially with adolescents35 and a trend towards support engaging youth in the planning and implementation process.63^–65 It thus appears that multicomponent models with multiple routes of entry may best solve the complex problem of childhood and youth physical inactivity.23 34 35

WHERE TO FROM HERE?

Researchers must continue to build the evidence for action. That said, some studies demonstrated effectiveness in a real-world setting and there is sufficient evidence to approach government and the school community to take and sustain a targeted investment in school health promotion.31 Indeed, it seems prudent to invest in promising practices in order to begin immediately to offset the trajectory towards low levels of physical activity and escalating obesity in children.

One size does not fit all. Environmental and whole school approaches offer the most promise for children. There is strong evidence for whole school multicomponent interventions and involving both family and youth increases the chance of success. Active school approaches that enhance PE, provide action breaks throughout the school day, integrate curricula that target sustained health behaviour change and sedentary behaviours and connect with families and the community, may be our way forward.

Although schools may be a key vehicle to improve public health there are many barriers that threaten the adoption and implementation of school health and physical activity models—even those that have proved to be effective.31 In order for physical activity initiatives to be adopted and sustained it is thus essential to engage school stakeholders (the end-users) in decision-making, be flexible, adaptable, easy to try and use and offer training and observable results for the end-user (teacher or administrator).31 66 These models begin to focus away from the child and towards shifting school culture so that teachers, administrators, parents and the community are supported and become part of the solution.

WHAT IS THE ROLE OF THE HEALTH PROFESSIONAL?

The trend towards a more physically active lifestyle demonstrated in school-based trials is important. Although modest, these upward shifts begin to offset the current downward trend in physical activity. These positive trends are also meaningful in the context of epidemic increases in obesity and chronic disease worldwide.

Health professionals are key players in any community. They can support physical activity initiatives by reiterating the “prevention” message to children and their parents in their clinical practice and when addressing the public. Health professionals who directly interact with children, youth or their families can also lend support to community and school-based efforts by: asking about and emphasising the importance of physical activity in discussions with patients; encouraging family-based activities; supporting local schools to adopt an “active school” approach and advocating for government and non-government agencies to support and sustain evidence-based and promising physical activity models within schools. Consistent and coordinated efforts across sectors and disciplines are needed to win the battle against childhood physical inactivity.