1. School of Health Sciences, Research Centre of Movement Science, University of Iceland, Reykjavík, Iceland;
2. Endurhaefing þekkingarsetur, Kópavogur, Iceland;
3. Centre for Clinical Research, Uppsala University, Region Västmanland, Västerås, Sweden;
4. Department of Clinical Sciences Lund, Division of Orthopaedics, Lund University, Lund, Sweden