title: Reply to the letter to the editor by Liu and Li.
authors.affiliation: Division Space Physiology, Institute of Aerospace Medicine, German Aerospace Center, Cologne, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Ganse
authors.forename: P-F
authors.initials: PF
authors.lastname: Yang
authors.forename: G-P
authors.initials: GP
authors.lastname: Brüggemann
authors.forename: L P
authors.initials: LP
authors.lastname: Müller
authors.forename: J
authors.initials: J
authors.lastname: Rittweger
authors.forename: T
authors.initials: T
authors.lastname: Koy
mesh_terms: D005260:Female; D006801:Humans; D008297:Male; D061848:Optical Imaging / Q000379:methods*; D013977:Tibia