Physical activity levels before and after the COVID-19 restrictions among Danish adolescents: a retrospective cohort study

Aims: It has been suggested that the COVID-19 restrictions may have negatively impacted physical activity (PA) levels, especially among adolescents, who often use organised sports to support their intrinsic motivation for staying active. This study aimed to investigate whether adolescents were less physically active after the COVID-19 restrictions compared with before and examine whether participation in organised sports has changed since the COVID-19 restrictions. Methods: This was a retrospective cohort study of Danish adolescents aged 15 to 19 years. Data was collected using a questionnaire in SurveyXact. The primary variable of interest was moderate or high-intensity PA frequency before and after COVID-19 restrictions (from March 11, 2020, to September 10, 2021). Secondary variables of interest included whether the PA was self-organised (e.g. running, hiking, going to a gym or cycling) or part of an organised sport delivered by a club or other association, before versus after the restrictions. Results: A total of 324 participants responded to the questionnaire. The relative risk of not performing PA at least twice per week after COVID-19 restrictions compared with before was significantly larger (1.44; 95%CI: 1.19 to 1.85, p = 0.005). Before the lockdowns, 190 (59%) were engaged in organised sports compared with 152 (47%) after the restrictions (relative risk: 1.51, 95%CI: 1.19 to 1.92, p < 0.001). Conclusions: Compared with activity levels before the pandemic, adolescents became significantly less physically active following the COVID-19 restrictions, beyond what is typically observed during adolescence. These results emphasise a need for strategies to increase PA levels among adolescents to minimise the long-term negative effects of physical inactivity during adolescence.