Published on in Vol 6 , No 12 (2018) :December
Preprints (earlier versions) of this paper are
available at
https://preprints.jmir.org/preprint/10972, first published
.

1 Physical Activity & Health, Department of Movement and Sports Sciences, Ghent University, Ghent, Belgium
2 Health Psychology, Department of Experimental Clinical and Health Psychology, Ghent University, Ghent, Belgium