title: The heart cannot pump blood that it does not receive.
authors.affiliation: Department of Internal Medicine, Academic Medical Centre, University of Amsterdam Amsterdam, Netherlands.
authors.forename: Wouter
authors.initials: W
authors.lastname: Wieling
authors.affiliation: Department of Cardiology, Academic Medical Centre, University of Amsterdam Amsterdam, Netherlands.
authors.forename: Frederik J
authors.initials: FJ
authors.lastname: de Lange
authors.affiliation: Department of General Medicine, Christchurch Hospital, University of Otago Christchurch, New Zealand.
authors.forename: David L
authors.initials: DL
authors.lastname: Jardine
keywords: cardiac output; gravitational stress; heart rate; orthostasis; orthostatic tolerance; vasoconstriction