Variability and cardiovascular homeostasis.
The inability to maintain the upright posture due to a failure in the arterial blood pressure regulatory mechanisms on return from space travel or after a period of head down tilt bed rest (HDBR) is the ultimate sign of cardiovascular deconditioning.  Yet, the final response of syncope is potentially heralded by a series of precursor events that can be quantified and analyzed in new, more insightful ways to attempt to understand the integrative nature of autonomic control of the cardiovascular system.
Hughson
R L
RL
Department of Kinesiology, University of Waterloo, Canada.
Gharib
C
C
D017704:Baroreflex / Q000502:physiology*; D001510:Bed Rest; D001794:Blood Pressure / Q000502:physiology*; D018493:Cardiovascular Deconditioning; D002346:Carotid Sinus / Q000502:physiology; D017709:Fractals; D018475:Head-Down Tilt; D006339:Heart Rate / Q000502:physiology*; D006706:Homeostasis / Q000502:physiology*; D006801:Humans; D010275:Parasympathetic Nervous System / Q000502:physiology*; D013026:Space Flight; D013057:Spectrum Analysis; D013564:Sympathetic Nervous System / Q000502:physiology