Sedentary Kids: The Health Impacts of Sedentary Behaviour On Children and Adolescents

By NASPEM member, Dr. David Dunstan


Since the declaration of the COVID-19 pandemic by the World Health Organisation on March 11, 2020, preventive measures such as home confinement and social distancing have become the new ‘norm’ around that world. Despite the effectiveness of such measures for virus control, legitimate concerns have been raised about the exacerbation of the perpetual pandemic – physical inactivity and excessive time spent sitting. Indeed, dramatic increases in sedentary behaviour (~3.1hr/d) and substantial reductions (33.5%) in physical activity have been reported globally during COVID-19 home confinement1.

Of course, this is against the already gloomy background that has been presented in recent research showing that children and teenagers are falling prey to sedentary lifestyles – spending more than two-thirds of their day sitting down2. A recent Australian study led by Dr Lauren Arundell from Deakin University in Melbourne, tracked nearly 400 students using special wearable devices that record time spent sitting, standing and lying during different parts of the day2. The typical pattern revealed that teenagers are driven to school, sit extensively at school, do their homework, then watch TV/ play computer games or scroll on their phones (as a parent this drives me crazy!). For sitting, class time was the biggest concern, with 75% of the class time spent sitting, followed by the evenings whereby 73% of the time was spent plonked on a chair.

The importance of addressing sedentary behaviour in children and adolescents has been reinforced by the inclusion of an explicit recommendation within the newly released World Health Organisation’s 2020 Physical Activity and Sedentary Behaviour Guidelines – “Children and adolescents should limit the amount of time spent being sedentary, particularly the amount of recreational screen time3.

The basis for the inclusion of this recommendation, in addition to the physical activity recommendations, comes from the growing body of evidence over the past decade showing that greater time spent sedentary, especially recreational screen time, is associated with poorer health outcomes3. Key take-aways from the extensive review undertaken by the WHO expert group for the evidence relating to children and adolescents are:

  • Greater time spent in sedentary behaviour is related to poorer health outcomes (low certainty evidence)
  • High sedentary behaviour (screen time) is associated with lower physical fitness and poorer cardiometabolic health (low certainty evidence)
  • High sedentary behaviour (screen time, television viewing and video game use) is significantly associated with unfavourable measures of mental health and behavioural conduct/pro-social behaviour (low-moderate certainty evidence)
  • High sedentary behaviour (screen time, television viewing) is associated with detrimental effects on sleep duration
  • The benefits of limiting the amount of sedentary behaviour for children and adolescents outweigh the harms

Although the WHO expert group concluded that there is insufficient evidence to specify time limits on sedentary behaviour, the Canadian 24hr Movement Guidelines for Children and Youth (ages 5-17 years)4 recommend “no more than 2 hours per day of recreational screen time” and “limited sitting for extended periods”. Similarly, the Australian 24-hr movement guidelines5 also recommend restricting sedentary screen time to < 2 hrs per day and “breaking up long periods of sitting as often as possible”.

Excitingly, we are already seeing the development of initiatives to combat the hazards of too much sedentary behaviour in children and adolescents such as the TransformUs! program6 that has been pioneered by Professor Jo Salmon and colleagues at Deakin University – a great program helping teachers incorporate movement and break up sitting in class in Victorian primary schools. Some useful ideas to help encourage children and adolescents to sit less and move more include:

  • Encourage students to get up and move around while in the classroom – dynamic or active class lessons
  • Getting creative with homework through modifying homework to include more group activities or activities that require intermittent standing and moving
  • Setting regular reminders on the phone to stand up and have regular active breaks
  • Challenging kids to be creative about ways to be active while in front of a screen, such as doing some stretches on the floor while watching TV or during the advertisements
  • Stand up and walk around while talking on the phone – walk and talk


1          Ammar, A. et al. Effects of COVID-19 Home Confinement on Eating Behaviour and Physical Activity: Results of the ECLB-COVID19 International Online Survey. Nutrients 12, doi:10.3390/nu12061583 (2020).

2          Arundell, L., Salmon, J., Koorts, H., Contardo Ayala, A. M. & Timperio, A. Exploring when and how adolescents sit: cross-sectional analysis of activPAL-measured patterns of daily sitting time, bouts and breaks. BMC Public Health 19, 653, doi:10.1186/s12889-019-6960-5 (2019).

3          World Health Organization. WHO guidelines on physical activity and sedentary behaviour. (2020).

4          CSEP. Canadian 24-Hour Movement Guidelines for Children and Youth (ages 5-17 years): An Integration of Physical Activity, Sedentary Behaviour and Sleep,

5          Australian Government Department of Health. Australian 24-Hour Movement Guidelines for Children and Young People (5-17 years) – An Integration of Physical Activity, Sedentary Behaviour and Sleep.,

6          TransformUs!,

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