Introduction :
The number of Emergency Department (ED) visits due to trampoline accidents has increased significantly over the last years. Previous research showed that many of these patients had taken insufficient safety measures as they were jumping with others and/or they were performing tricks. It is still unknown, however, why people perform risky behaviour. If our goal is to change their behaviour, we need to develop an understanding of their actions. We are particularly interested in adolescents aged 12-15, as this group remains underrepresented in research compared to younger children. Furthermore, this group may provide more opportunities for behavior change, including strategies to increase knowledge and awareness.

Objectives:
This study aims to understand risky behaviour of adolescents aged 12-15 years and design effective behavioural interventions to prevent severe trampoline accidents.

Methods:
Various qualitative research methods were combined to analyse risky behaviour concerning trampolines among adolescents 12-15 years of age. Observational analyses were performed in three different indoor trampoline parks. Additionally, interviews were conducted with adolescents (n=15), their parents (n=6) and employees (n=3) of the parks. Lastly, a social media analysis with different online platforms was carried out. A behavioural change model was applied to the data to identify factors influencing the children’s risky behaviour. Subsequently, behavioural change techniques were matched to develop potentially effective interventions for behaviour change.

Results:
Risky behaviour was mainly influenced by social norms, comforts, and motivation. Adolescents were mainly inattentive and inconsiderate about the risks, e.g., not paying attention to others playing on the same trampoline. Furthermore, adolescents often copied behaviour of others while playing, which became risky when they tried tricks that were too difficult for them to perform. Adolescents also perceived low risk and were primarily motivated by jumping together, which they found more fun than jumping alone. To design effective interventions, various behaviour change techniques were identified, including altercasting, salience, and loss aversion.

Conclusion :
A behavioural science approach successfully led to various behaviour change strategies for preventing severe trampoline accidents among adolescents. Understanding adolescent’s risky behaviour provided evidence-informed starting points for designing interventions or campaigns to increase child safety. 6. Keywords  Trampoline accidents, Emergency Department, Behavioural design.