ABSTRACT
This chapter examines bed rest as a ground-based analog for the effects of microgravity on integrative physiological systems as encountered in space flight. Commonly used ground-based analogs include bed rest studies and water immersion. Deconditioning following either weightlessness or bed rest shares many effects and symptoms characterized by orthostatic intolerance (OI). Studies in both microgravity and bed rest conditions can provide information on the physiology and clinical problems related to OI and potential countermeasures for patients suffering from OI. Bed rest studies also allow for relatively easy implementation and testing of countermeasures to reduce the detrimental effects of microgravity. Information derived from tests of possible countermeasures for spaceflight deconditioning will be critical for microgravity exposures of long duration as will be encountered, for example, during a mission to Mars. Bed rest is global models for the effects of microgravity, influencing a number of systems simultaneously.
