Physical activity for children and young people (5-17 years)

This is an English summary of the Danish report: Fysisk aktivitet for børn og unge (5-17 år) 

'Physical activity for children and young people (5-17 years) – knowledge about prevention and health benefits' presents the evidence on the association between physical activity, sedentary behaviour and health among children and young people aged 5-17 years. The report includes scientific literature from the Danish Health Authority (Sundhedsstyrelsen) and international systematic reviews conducted by research institutions and authorities from various countries: World Health Organization, USA, Canada, and Australia.

In the report the level of the evidence is described as strong, moderate, low, very low or insufficient. The indicated levels of evidence are based on the assessment made in the literature reviews that form the basis of the report. In these literature reviews, the level of evidence is based on an evaluation of the amount and quality of research in the area and whether there is consistency in the results of the studies. Strong evidence indicates great confidence in the observed relationship between physical activity and a given health outcome. In order to obtain strong evidence for an association, much research and several high-quality studies that point in the same direction is required. In the case of insufficient evidence, there is insufficient research to determine whether there is an association. Amongst other things, this may be because it has not yet been sufficiently investigated, which often characterizes new areas of research.

Physical activity and health

• There is moderate certainty evidence that physical activity is associated with improved cardiorespiratory fitness, bone and muscle strength and cardiometabolic health in children and adolescents, including improved blood pressure, cholesterol levels and reduced risk of insulin resistance.
• There is moderate certainty evidence that physical activity reduces the risk of developing depression. Also, there is moderate certainty evidence that physical activity reduces depressive symptoms in children and adolescents with and without major depression.
• There is moderate certainty evidence that physical activity has positive effects on children’s and adolescents’ cognitive function and academic performance, in particular the executive function (Executive functions are a set of cognitive processes that are necessary for the cognitive control of behaviour. Executive function enables us to plan, focus attention, remember instructions, and juggle multiple tasks successfully.)
• There is low certainty evidence that physical activity is positively associated with maintenance of healthy weight status in children and adolescents.

Sedentary behaviour and health

Sedentary behaviour is a relatively new area of research that has received increased attention as more knowledge has emerged of the adverse effects of sedentary behaviour on health in children and young people.

• There is low certainty evidence that screen time is related to lower cardiorespiratory fitness and poorer cardiometabolic health in children and adolescents.
• There is very low to moderate certainty evidence that screen time is associated with unfavourable risk factors of adiposity in children and adolescents.
• There is very low to moderate certainty evidence that screen time has a negative impact on children’s and adolescents’ mental health measured by self-esteem, depression, and prosocial behaviour. (Pro-social behaviour is any behaviour that is intended to benefit another person or persons. Pro-social behaviour refers to social competencies and ability to form social relationships.)

Dose-response relationship in relation to amount and intensity of physical activity and sedentary behaviour

Only a few studies have examined the dose-response relationship between physical activity, sedentary behaviour and health among children and adolescents. The literature indicates that there is no lower threshold for benefit, as the beneficial effects is seen at all levels of physical activity.

• There is moderate certainty evidence that greater amounts of moderate- and vigorousintensity physical activity are associated with improved cardiorespiratory fitness in children and adolescents.
• There is insufficient evidence to determine a dose-response relationship between physical activity and cardiometabolic health, weight status, bone and muscle strength, mental health, and cognitive function among children and adolescents. However, studies find that moderate to high intensity physical activity shows to have the greatest beneficial effect on these outcomes.
• There is insufficient evidence to determine a dose-response relationship between sedentary behaviour and health of children and adolescents.

Type and domain of physical activity

There is a difference in the physical activity level of children and young people during the day as well as during the week depending on what activities they do. In general, Danish children and adolescents are more physically active on weekdays than on weekends. In addition to physical activity during school time, active transport and participation in leisure activities are important elements in children and young people's daily physical activity level. Few studies have examined the effect of different types and domains of physical activity on the health of children and adolescents.

• There is moderate certainty evidence that muscle-strengthening activities in combination with aerobic/cardiovascular activities of moderate to high intensity has additional health benefits in children and adolescents. Aerobic/cardio physical activity increases cardiorespiratory health while muscle-strengthening activity improves bone and muscle strength.
• There is insufficient evidence to determine whether the effect of physical activity on health varies by domains (e.g., active transportation (walking and cycling) vs. organised sports).

Knowledge gaps and future perspectives

Movement behaviours in childhood and adolescence form the basis of movement behaviour in adulthood. In addition, an active life for children and young people creates a robust foundation for health and resistance to illness and morbidity later in life. The evidence shows that physical activity of moderate to high intensity is associated with several positive effects on children and adolescents' health and development. However, it is estimated that only 26% of Danish 11-15- year-olds meets the physical activity guidelines of at least 60 minutes a day at moderate to high intensity, and that they spend on average about 11 hours on sedentary activities on weekdays.

Within the age group 5-17 years, there are large developmental differences and opportunities for being physically active. A 5-year-old child and adolescent 17-year-old adolescent are at very different developmental stages and also have different movement pattern, motor skills and fitness levels. These differences affect how physical active they are and which activities they do but also how it effects their health. Therefore, future research should differentiate within the age group to gain more knowledge about how physically active children and adolecents should be to improve their health according to individual age and developmental stage. In addition, there is a need for more knowledge about the dose-response relationships and variations by type and domain of physical activity.

Physical activity is of great importance for the health of children and adolescents. However, there is still sparse knowledge about the several health effect of physical activity, in particular mental health. Recent national statistics point to an increase in the proportion of young people with poor mental health and well-being. Future research is needed to gain more knowledge about the causal relationships and understand how physical activity is related to children and adolescents’ health. It is also important to support knowledge and methods to stimulate Danish children and adolescents to be physical active and maintain a physically active in their everyday life.