1. Department of Rehabilitation and Sports Medicine, 2nd Medical Faculty, Charles University and Motol University Hospital, 150 06 Prague, Czech Republic
2. Physiotherapy Department, Evangelisches Krankenhaus Düsseldorf Sozialpädiatrisches Zentrum, 40217 Düsseldorf, Germany
3. Queen Square Centre for Neuromuscular Diseases, University College London and National Hospital for Neurology and Neurosurgery, Queen Square, London WC1N 3BG, UK