1. Erasmus Medical Center; Department of General Practice; Rotterdam Netherlands
2. University Medical Center Groningen, University of Groningen; Department of Health Sciences, Community and Occupational Medicine; Groningen Netherlands
3. Rotterdam University of Applied Sciences; Research Centre Innovations in Care; Rotterdam Netherlands
4. VU University Amsterdam; Department of Health Sciences, Faculty of Earth and Life Sciences; PO Box 7057 Room U454 Amsterdam Netherlands 1007 MB
5. Aarhus University Hospital; Department of Physiotherapy & Occupational Therapy; Aarhus Denmark
6. University of Southern Denmark; Center for Muscle and Health; Odense Denmark