1. J Harting, PhD, BA in Physiotherapy, is Postdoctoral Researcher, IQ Healthcare, University Medical Centre St Radboud, PO Box 9101, 6500 HB Nijmegen, the Netherlands, and Department of Social Medicine, Amsterdam Medical Centre, Amsterdam, the Netherlands.
2. GMJ Rutten, MPT, MPH, is a PhD student, IQ Healthcare, University Medical Centre St Radboud, and a practicing manual physical therapist, Uden, the Netherlands.
3. STJ Rutten, MPT, MPH, is a practicing manual physical therapist, Aachen, Germany.
4. SP Kremers, PhD, is Assistant Professor, Department of Health Promotion, Maastricht University, the Netherlands.