Published on in Vol 23, No 2 (2021): February
Preprints (earlier versions) of this paper are
available at
https://preprints.jmir.org/preprint/18161, first published
.

1 Department of Behavioural Science and Health, University College London , London , GB
2 Faculty of Science and Engineering, Anglia Ruskin University , Cambridge , GB
3 Six to Start , London , GB
4 Institute of Health Informatics, University College London , London , GB
5 Department of Psychology and Sports Science, University of Hertfordshire , Hatfield , GB
*these authors contributed equally