The authors have declared no competing interest. DRKS00027907 This study is part of the Research Unit FOR 5177 funded by the German Research Foundation (DFG), Hendrik Schmidt: SCHM 2572/11-1, SCHM 2572/12-1, SCHM 2572/13-1; Sandra Reitmaeier: RE 4292/3-1, Matthias Pumberger: PU762/1-1. The analyses and contribution from the Hochschule fuer Gesundheit were funded, in part, by grant number 50WK2273A (to DLB) from the German AeroSpace Center (DLR).