1. R.H.M. Nijland, MSc, Department of Rehabilitation Medicine, Research Institute MOVE, VU University Medical Centre, Amsterdam, the Netherlands.
2. E.E.H. van Wegen, PhD, Department of Rehabilitation Medicine, Research Institute MOVE, VU University Medical Centre, Boelelaan 1117, 1081 HV Amsterdam, the Netherlands.
3. B.C. Harmeling-van der Wel, Department of Rehabilitation Medicine and Physical Therapy, Erasmus MC University Hospital, Rotterdam, the Netherlands.
4. G. Kwakkel, PhD, Department of Rehabilitation Medicine, Research Institute MOVE, VU University Medical Centre, and Department of Rehabilitation Medicine, Rudolf Magnus Institute of Neuroscience, University Medical Center Utrecht, Utrecht, the Netherlands.