Funding for this research was provided by:
FP7 Information and Communication Technologies (288940)
Received: 17 April 2019
Accepted: 9 October 2019
First Online: 3 November 2019
Ethics approval and consent to participate
: All participants provided written informed consent and the Ethics Committee of the German Sport University Cologne had approved the study (Wave 1 Registration Nr: 5/2014 and Wave 2 Registration number: 38/2015).
: Not applicable.
: The authors declare that they have no competing interests.