1. Centre for Health and Sport Sciences; School of Education; University of Iceland; Reykjavik Iceland
2. Department of Epidemiology and Biostatistics; Imperial College London; London UK
3. Research Centre for Movements Sciences; University of Iceland; Reykjavik Iceland
4. Department of Psychology; School of Health Sciences; University of Iceland; Reykjavik Iceland
5. Icelandic Directorate of Education; Kopavogur Iceland
6. Department of Sport and Physical Activity; Western Norway University of Applied Sciences; Bergen Norway