Abstract
Children in Germany showed positive physical activity changes during the first Covid-19 lockdown in April 2020, but it is unclear how the changes relate to population density, which we investigated in a longitudinal sample of 1711 youth (4-17 years). For each ten citizens more per km(2), less positive physical activity changes were observed. For example, a child living in an area with 100 citizens/km(2) increased daily life physical activity by 44.50 min/day, whereas a child living in an area with 3000 citizens/km(2) only engaged in an additional 9.70 min/day. Policymakers should ensure that youth in densely populated areas have access to physical activity opportunities during the pandemic.