1. Division of Community Medicine, Department of Medical and Health Sciences, Linköping University, Linköping, Sweden
2. Football Research Group, Linköping, Sweden
3. Aspetar Orthopaedic and Sports Medicine Hospital, Doha, Qatar
4. Region Östergötland, Center for Health Services Development, Linköping, Sweden
5. United States Olympic Committee, Colorado Springs, Colorado, USA
6. United States Coalition for the Prevention of Illness and Injury in Sport, Colorado Springs, Colorado, USA
7. Department of Family Practice, University of British Columbia, Vancouver, British Columbia, Canada