The Effect of Standing Desks in Secondary Schools on Sedentary Behavior and Cognitive Performance in Flemish Adolescents

Introduction:

Sedentary behavior is defined as "any waking behavior characterized by an energy expenditure ≤1.5 metabolic equivalents (METs), while in a sitting, reclining or lying posture". Among adults, evidence suggests that prolonged time spent in sedentary behavior is positively associated with type 2 diabetes, cardiovascular diseases, metabolic syndrome and all-cause mortality. Although this association is less consistent among children and adolescents, several studies and reviews have found adverse associations between sedentary time and health outcomes in children and adolescents too. Additionally, a review of reviews has found evidence for an association between screen-time behaviors (i.e. specific sedentary behaviors) and obesity and moderate evidence for an association between screen-time behaviors and blood pressure, total cholesterol, self-esteem, social behavior problems, physical fitness and academic achievement, and these associations are largely independent from moderate- to vigorous physical activity. Moreover, since sedentary time in early life tracks into adulthood where it can have potential health implications, strategies are needed to reduce sedentary time in children and adolescents. Children and adolescents spend more than 60% of the day (waking hours) sedentary. In addition, more than 65% of the time at school is spent in sedentary activities. Therefore, the classroom can be considered an important setting for implementing specific strategies to reduce sedentary time in this target group.

A potential environmental strategy to reduce sedentary time during school hours is replacing traditional desks and chairs with standing desks. Although there is currently no general consensus on the health benefits of implementing standing desks into the classroom, this strategy might have a beneficial impact on children's energy expenditure. For sedentary time, standing time and step counts, results are currently mixed. More research is needed to make strong conclusions, as previous studies often had a low quality design. Furthermore, it is also advocated to focus on secondary schoolchildren, as the majority of studies have been conducted in primary schools and the level of sedentary behavior is high in secondary schools.

However, qualitative data from teachers in secondary schools from a study conducted previously by our research group (see references) indicated that not all teachers are convinced of the added value of implementing standing desks in secondary schools. The major worry is that standing up during lessons might impact pupils' academic performance. As this is a genuine concern, robust evidence that standing desks have positive effects on pupils' cognitive and academic performance is needed to support the introduction of standing desks in schools. It has indeed been advocated to capture such outcomes in further research, as this information is of primary importance for schools. A potential mechanism could be that standing is associated with increased energy expenditure, resulting in an effect on cognitive performance. Currently, two very small studies provide support at the proof of concept level and pilot data that standing desks might impact cognitive function positively among children or adolescents. A pilot study that explored neurocognitive benefits of standing desks in 14-year-olds across secondary schools found that the use of standing desks was associated with significant improvements in executive function and working memory capabilities over a period of about six months. The authors advocated that more research is needed, as the study was conducted in one school with no comparison group and a relatively small study sample (n = 27). Another pilot study investigated the effect of implementing standing desks for 11 weeks into a primary school classroom, and found that the intervention group significantly improved on the Digit Task Span test compared to the control group. No differences were found for the Eriksen flanker task, suggesting that standing desks are more likely to affect the short-term working memory than the inhibitory control. However no firm conclusion can be drawn from this study because its sample size was too small (n = 38) and the intervention period too short. More research is needed to provide a definitive answer.

Finally, in our previous study, only three standing desks per class were installed. The reason to choose three desks was that schools often report the high costs of standing desks as a barrier to implement them. This implied that practicable solutions need to be provided (such as installing a limited amount of desks per class) to broadly promote and disseminate the use of standing desks in schools. In addition, the financial restrictions within the project did not allow the researchers to install a large amount per class. However, this caused that pupils only stood up for 50 minutes per week on average. In the pilot study of Wick et al. who investigated the effect on cognitive function, it was recommended that using the desks for at least 1 hour per school day would be advisable to improve cognitive function. Thus, it will be important for the evaluation to install a sufficient amount of standing desks in every classroom to ensure that adolescents can stand up long enough. In the methodology of this proposal, this will be further specified.