More physical activity and less sitting in children: Why and how? - 02/10/14

Doi : 10.1016/j.scispo.2014.08.002

G. Cardon ^⁎, M. De Craemer, I. De Bourdeaudhuij, M. Verloigne
Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium

^⁎Corresponding author.

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Résumé

Introduction

The high prevalence of overweight and obesity is a worldwide health problem and is already manifesting in elementary school and even preschool children. Childhood overweight is associated with serious health problems, the risk of premature illness and early death later in life. Furthermore, overweight in early childhood has shown to increase the likelihood of being obese in later childhood and even tracks into adulthood in one-third to one-half of cases. A recent cross-sectional study within the framework of the ENERGY-project (www.projectenergy.eu/) collected anthropometric data from 10- to 12-year-old children in seven European countries [1]. Results demonstrated that 25.8% of boys were overweight, from which 5.2% obese and that 21.4% of girls were overweight, from which 4.1% obese. The prevalence rates varied greatly across European countries. The results clearly established the highest prevalence rates in the more southern and central European countries, which is similar to the results of previous European studies. Also in preschool aged children, the highest prevalence of overweight and obesity has been found in southern Europe (i.e. Spain and Greece). Within the framework of the ToyBox-study (www.toybox-study.eu/) secondary data analyses in four- to seven-year-old preschool children from six European countries (Belgium, Bulgaria, Germany, Greece, Poland, and Spain) showed that 8 to 30% of European preschool children have overweight and 1% to 13% of them are obese [2]. Further, previously published figures from developed countries show that the prevalence of overweight and obesity among children under the age of five increased in developed countries from 8% in 1990 to 12% in 2010 with an expected prevalence of 14% in 2020. Estimates of childhood obesity generally tend to be higher in the US, but it appears that the gap between continents is getting smaller if US data are compared to European data. Although childhood obesity is currently showing rather stabilizing trends, the prevalence rates are still high worldwide, which suggests that childhood obesity remains a major public health issue. Changes in lifestyle behaviour are likely to be the main cause of the increase in overweight and obesity, rather than changes in biologic or genetic factors. Weight gain is determined by the cumulative effect of low levels of physical activity, high levels of sedentary behaviour, and unhealthy dietary behaviours, also referred to as energy balance-related behaviours. In this abstract, we will focus on two important energy balance-related behaviours in children: physical activity and sedentary behaviour. Establishing healthy lifestyle behaviours – such as more physical activity, and less sedentary behaviour – is already important at an early age, since these healthy energy balance-related behaviours track into later life, and even into adulthood. The preschool age may be a critical period for preventing overweight and obesity since weight-related behavior patterns and habits are not established yet. Furthermore, early childhood is the critical period for the adiposity rebound. At this age, body adipose tissue reaches a post infancy low point (typically at the age of four to six years). In this abstract, we will focus on preschoolers and elementary school children. Health behaviours may even be important at younger age, but up to now very little is known on these behaviours in toddlers.

Physical activity: definition, prevalence and guidelines

Physical activity can be defined as “any bodily movement produced by skeletal muscles that results in energy expenditure”. Next to the prevention of overweight, participation in sufficient levels of physical activity is also important for the motor, social and cognitive development of children. It has been recommended for elementary school children to engage in at least 60minutes/day in moderate to vigorous intensity physical activity. Recently, in Australia, Canada and the US, new physical activity guidelines were established specifically for preschool children [Australian Government Department of Health and Ageing (2009), Canadian Public Health Association (2007) and Department of Health UK PA guidelines (2011)]. These guidelines propose that preschool children should engage in 180minutes of total physical activity per day, irrespective of intensity. Despite the evidence that sufficient physical activity is beneficiary and healthy, it is shown that considerable numbers of children do not comply with the physical activity recommendations. Based on accelerometer data within the ENERGY study, the mean level of moderate to vigorous physical activity per day among 10- to 12-year-old children from Belgium, Greece, Hungary, the Netherlands and Switzerland was 32minutes for girls and 43minutes. Only 5% of girls and 17% of boys reached the recommendation according to the cut-points of Treuth. Even in most preschool children, physical activity levels are low. In our Belgian study in four- and five-year-old preschoolers, accelerometer-based data showed that only 15% of the day was spent in total physical activity. Furthermore, Belgian preschoolers engaged in moderate to vigorous physical activity for only 34minutes a day. In the scope of the ToyBox-study, it was found that Belgian preschoolers on average spend 121±47min on total physical activity and only 9% fulfill the current physical activity recommendation according to the cut-points of Reilly.

Sedentary behaviour: definition, prevalence and guidelines

Sedentary behaviour can be defined as any waking behaviour characterized by an energy expenditure that is less than or equal to 1.5 METs (Metabolic Equivalents) while in a sitting or reclining posture (Sedentary Behaviour Research Network, 2012). Such behaviours generally include television viewing, electronic game use, reading, and computer use. For a long time, having a sedentary lifestyle was considered the opposite of being sufficiently physically active, but research has demonstrated that sedentary behaviour and physical activity are two unique behavioural constructs, independently related to various health outcomes, such as overweight and obesity. Many children that are able to attain the recommended physical activity levels still spend a large proportion of time in a sedentary way, suggesting that sedentary behaviour cannot be defined as failure to meet the physical activity guidelines. According to UK Start Active Stay Active (2011), young children should minimize the amount of time spent being sedentary (restrained or sitting) for extended periods (with the exception of sleeping). While there are many other forms of sedentary behaviour, this behaviour is often performed in the context of screen-based entertainment, particularly in television viewing. This screen-based entertainment has been shown to be associated with some negative health outcomes (e.g., lower bone density, adverse consequences for educational achievement, anti-social and aggressive behaviour) in two- to four-year-old children and it was shown that this behaviour moderately tracks from childhood into later years. Screen-time is frequently used as a proxy marker of overall sedentary behaviour. Consequently, next to the suggestion to limit prolonged periods of sitting, sedentary behaviour guidelines also include specific recommendations for the amount of screen-time per day. Recently developed guidelines on sedentary behaviour recommend children to spend no more than two hours per day on screen-time and to limit sedentary transport, extended sitting time and time spent indoors. Furthermore, recent guidelines recommend that preschool children (one- to five-year-olds) should limit watching television and the use of other electronic media – like computer, DVDs and other electronic games – to less than one or two hours daily (Australian Department of Health and Ageing 2010, Canadian Sedentary Behavior Guidelines, 2012) or no more than two hours daily (American Academy of Pediatrics, 2006). Despite the introduction of these guidelines, children spend a considerable amount of time in sedentary pursuits throughout the day. Recent accelerometer-based data in elementary schoolchildren aged 10–12 years showed that European children spent on average 65% of their waking time in sedentary activities with boys and girls spending on average of 3.5 and 3hours per day respectively on screen-time behaviours (television and computer time). Even at preschool age sedentary behaviour is very common. Inadequate data exists on the current prevalence of preschool children's levels of sedentary behaviour, and various measurement and analytic issues hamper comparison of findings between studies. However, most studies using objective methods (such as accelerometry) to assess time in sedentary behaviour report that children spend between 50% and 80% of their time being sedentary. Furthermore, parental proxy-reports indicated that Belgian preschoolers spent on average 1.2hours and 2.3hours in TV viewing and computer use on week and weekend days respectively. Similarly, the Australian Health Survey (2011–2012) reported that two- to four-year-olds spent 1.4hours per day watching TV, DVDs or playing electronic games, while US preschoolers (mean age 4.4 years) were exposed to 3.6hours of screen-based entertainment daily at home.

More physical activity and less sitting in children: how?

The importance of a socio-ecological approach to health promotion has become widely recognized. According to this approach, health promotion initiatives should not only focus on individual factors, but the broader cultural, social and economic environment of the individual has to be taken into account. For the promotion of healthy behaviours in children, not only the children but also the parents and other caregivers, like day-care personnel and teachers have to be focused on and the home environment as well as the school or day-care environment are important. Interventions should aim at creating an environment supportive of healthy behaviours. On the other hand, strategies should take into account personal factors, like age and social economical status and should consider personal barriers of the children and parents and teachers too. Within several projects (ENERGY, IDEFICS, and ToyBox) [3], the Intervention Mapping protocol has been used as the conceptual framework for developing an intervention. Using the Intervention Mapping protocol has the benefit that the intervention is developed in a systematic, evidence-based and theory-driven manner. Every decision during the development and implementation protocol is well thought-out and carefully considered. In addition, different implementation levels are included in the Intervention Mapping protocol (e.g., individual level, interpersonal level, organisational level), which heightens complexity, but might also raise effectiveness. Based on the Intervention Mapping protocol, matrices have been developed to design interventions to promote more physical activity and less sitting in children. These matrices can be used for future intervention development.

Physical activity: some intervention approaches

Schools are considered to be one of the preferred intervention environments for increasing daily physical activity in children. Consequently, helping schools to fulfill their physical activity promoting role should be a public health priority, especially since a recent study within the ENERGY-project in 10-to 12-year-olds showed that only a small amount of time at school (5%) was spent in moderate to vigorous physical activity. The Toronto Charter for Physical activity outlines a “whole-school” approach as one of the seven “best investments” for physical activity, which are supported by good evidence of effectiveness and that will have worldwide applicability. A “whole-school” approach to physical activity involves prioritizing regular, highly-active, physical education classes; providing suitable physical environments and resources to support structured and unstructured physical activity throughout the day; supporting walk/cycle to school programmes and enabling all of these actions through supportive school policy and engaging staff, students, parents and the wider community. However, it was found in Belgian schools that after school physical activity programmes and the promotion of active commuting are not widely implemented [4]. Further efforts are needed to convince and help schools to increase parental and pupil involvement and to build a policy on school-community partnerships to provide PA opportunities for all children. In preschoolers, studies on interventions to promote physical activity are scarce. A review within the ToyBox-study showed that interventions that (1) combined high levels of parental involvement and interactive school-based learning, (2) targeted physical activity and dietary change and (3) included long-term follow-up, appeared most effective to prevent obesity in preschool aged children. It was suggested that interventions should also focus on developing children's and parents perceived competence at making physical activity and dietary changes. Within the ToyBox-study a kindergarten-based intervention with parental involvement was developed [5]. Intervention effects were evaluated on Belgian preschoolers’ objectively measured physical activity. In the total sample, an effect was found on moderate to vigorous physical activity during after school hours. Larger effects were found in sub-groups, namely in preschool boys and in preschoolers from preschools with a high socio-economic status. Based on the ecological model, some studies looked specifically into school environmental factors in relation to children's physical activity. In that regard, we found that young children's physical activity during recess was associated with modifiable playground factors. Furthermore the provision of more play space increased physical activity levels during recess in elementary schoolchildren as well as in preschoolers [6]. However, the provison of markings and play materials was only effective in increasing physical activity levels in elementary schoolchildren and not in preschoolers [7]. The latter emphasizes the age-specific approach and that “one intervention fits all” does not hold.

Sedentary behaviour: some intervention approaches

Up to now, only limited research has been done on sedentary behaviour in children and only a few interventions to decrease sedentary behaviour have been published. While objective data show high levels of sedentary behavious in young childen, parents and teachers do not perceive this as such. They also do not think high levels of television time are problematic in young children. Consequently, interventions to decrease sedentary behaviour should first raise awareness on this health behaviour. Furthermore, studies consistently report a positive association between parents’ and children's television viewing time and clearly show the effect of parental modelling on childrens’ television viewing behaviour, which highlights the importance of parental involvement in interventions [8]. Up to now, only few interventions focusing on sedentary behaviour have been evaluated. The UP4FUN intervention did not result in an effect on children's sedentary time [9]. The intervention consisted of 1 or 2 lessons per week during 6weeks implemented by the class teachers. The researchers stated that sedentary behaviours could have a strong habitual component and are therefore difficult to change, especially in a short intervention period. In a previous studies evaluating back pain prevention efforts in schoolchildren and comparing a traditional school with a moving school, the use of environmental components in the classroom (e.g. standing desks, swiss balls) showed promising effects on sitting posture and sedentary behaviours [10]. This suggests that structural changes in the school environment are a more promising strategy to change sedentary behaviour. Effects of the ToyBox intervention were evaluated in Belgian preschoolers. Some small effects were found on computer time, but no intervention effects were found on objectively measured total sedentary time in the total sample. However, important intervention effects were found in important sub-groups (i.e., girls, in preschoolers of low socio-economic status preschools and in those with the highest levels of total sedentary time at baseline).

Conclusion

High prevalence rates of overweight and obesity in children, the fact that considerable numbers do not reach the physical activity guidelines and that sedentary behaviour is very common already at young age, advocate the need for effective interventions focusing on more physical activity and less sitting in children. A socio-ecological approach and the involvement of schools and preschools as well as parents are important for interventions to promote more physical activity and less sitting. Some physical activity promotion interventions are found to be effective, but effects are often rather limited and the implementation is often lacking. Therefore, future studies might need to include a more participatory approach during the development of the intervention to increase effectiveness. Further study is also needed to evaluate interventions that promote less prolonged sitting in children. This seems particularly challenging due to the strong habitual component. Interventions including more environmental components seem promising and need to be further explored.

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