1. H. Beckerman, PT, PhD, is Senior Researcher, Department of Rehabilitation Medicine, VU University Medical Center, PO Box 7057, 1007 MB Amsterdam, the Netherlands, and EMGO Institute for Health and Care Research, VU University and VU University Medical Center, Amsterdam, the Netherlands.
2. V. de Groot, MD, PhD, is Rehabilitation Physician and Senior Researcher, Department of Rehabilitation Medicine, VU University Medical Center, and EMGO Institute for Health and Care Research, VU University and VU University Medical Center.
3. M.A. Scholten, MD, was a medical student, Faculty of Medicine, VU University Medical Center, at the time of the study.
4. J.C.E. Kempen, PT, MSc, is a PhD candidate, Department of Rehabilitation Medicine, VU University Medical Center, and EMGO Institute for Health and Care Research, VU University and VU University Medical Center.
5. G.J. Lankhorst, MD, PhD, is Rehabilitation Physician, Professor, and Head of the Department, Department of Rehabilitation Medicine, VU University Medical Center, and EMGO Institute for Health and Care Research, VU University and VU University Medical Center.