Ane Sofie Kokkvoll1,2, Sameline Grimsgaard3, Trond Flaegstad2,4, Lars Bo Andersen5,6, Geoff D C Ball7, Tom Wilsgaard3, Inger Njølstad3. 1. Department of Paediatrics, Finnmark Hospital Trust, Hammerfest, Norway. 2. Paediatric Research Group, Faculty of Health Sciences, UiT The Arctic University of Norway, Tromsø, Norway. 3. Department of Community Medicine, Faculty of Health Sciences, UiT The Arctic University of Norway, Tromsø, Norway. 4. Department of Paediatrics, University Hospital of North Norway, Tromsø, Norway. 5. Faculty of Education, Arts and Sport, Campus Sogndal Western Norway University of Applied Sciences, Sogndal, Norway. 6. Department of Sports Medicine, Norwegian School of Sport Sciences, Oslo, Norway. 7. Department of Paediatrics, Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada.