Funding for this research was provided by:
Bundesministerium für Bildung und Forschung (01EL1422B, 01EL1822B)
Staats- und Universitätsbibliothek Bremen
Received: 14 October 2020
Accepted: 2 April 2021
First Online: 26 April 2021
: The OUTDOOR ACTIVE study was approved by the ethical committee of the University of Bremen. All participants provided written informed consent.
: Not applicable.
: The authors declare that they have no competing interests.