1. C. Ammann-Reiffer, PT, MPTSc, Pediatric Rehab Research Group, Rehabilitation Center for Children and Adolescents, University Children's Hospital Zurich, Affoltern am Albis, Switzerland; Children's Research Center, University Children's Hospital Zurich, Zurich, Switzerland; and Department of Epidemiology, Musculoskeletal Research Group CAPHRI, Maastricht University, Maastricht, the Netherlands. Ma
2. C.H.G. Bastiaenen, PhD, Department of Epidemiology, Musculoskeletal Research Group CAPHRI, Maastricht University.
3. R.A. de Bie, PhD, Department of Epidemiology and Institute for Education, Maastricht University, and CAPHRI Research School, Maastricht, the Netherlands.
4. H.J.A. van Hedel, PT, PhD, Rehabilitation Center for Children and Adolescents, University Children's Hospital Zurich, and Children's Research Center, University Children's Hospital Zurich.