1. Department of Preventive and Rehabilitative Sport- and Exercise Medicine, Institute for Cardiology and Sports Medicine, German Sportuniversity Cologne , Am Sportpark Müngersdorf 6, D-50933 Köln , Germany
2. Curschmann Klinik , Saunaring 6, D-23669 Timmendorfer Strand , Germany
3. Faculty of Medicine, University of Lübeck , Ratzeburger Alle 260, 23562 Lübeck , Germany