1. Department of Sports Medicine, Justus-Liebig University Giessen, Kugelberg 62, 35394 Giessen, Germany
2. Mathematical Institute, Justus-Liebig University Giessen, Arndtstraße 2, 35392 Giessen, Germany
3. Department of Sports Medicine, University Hospital of Tuebingen, Hoppe-Seyler-Straße 6, 72076 Tuebingen, Germany
4. Division of Sport and Rehabilitation Medicine, University Hospital Ulm, Parkstraße 11, 89075 Ulm, Germany