Background:
Although children seem to be at a lower risk for severe COVID-19 infection, governmental regulations to prevent the spread of the virus possibly affect their lifestyle and related health. In the Netherlands, controlled lock-down measures included closure of schools, daycare and sports facilities.

Objective:
Investigating self-reported and objectively measured physical activity (PA) and screen time among Dutch children at different time points before and during the COVID-19 pandemic.
Setting and participants: Data derived from two different cohorts were used. In cohort A (102 children, 10.5 ± 3.6 year, 42.4% boys) PA and screen time were evaluated with a questionnaire regarding the pre-pandemic situation and a follow-up questionnaire regarding the situation during the COVID-19 pandemic. Cohort B was derived from an ongoing study, in which 131 children (10.2 ± 0.9 year, 43.5% boys) filled out questionnaires on PA and screen time and wore an ActiGraph accelerometer, after reopening of schools and one year earlier.

Results:
Seventy-five percent of children in cohort A reported less total PA during the controlled lock-down. Total screen time on weekdays significantly increased by 34± 105 min/day. Compared to May 2019, children in cohort B reported to spend less time on sports during the pandemic. Even after reopening of schools, objectively measured sedentary time was increased with 45 ± 67 min/day compared to May 2019. Children that spent a minimum of 60 min/day on moderate-to-vigorous intensity PA was decreased from 64% to 20%. Screen time was increased by 59 ± 112 min/day on week days and 62 ± 130 min/day on weekend days for children in cohort B.

Conclusion:
During the COVID-19 pandemic, PA levels decreased and screen time increased during and directly after the controlled lockdown. This is alarming as a healthy, active lifestyle in children is crucial in preventing chronic diseases.