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Updated: Feb 13, 2026

Tilt Testing with Combined Lower Body Negative Pressure: a "Gold Standard" for Measuring Orthostatic Tolerance
Published on: March 21, 2013
REACTION OF THE CARDIOVASCULAR, SYSTEM TO ORTHOSTATIC TESTING DURING EXTENDED HEAD-DOWN BED REST AS A FUNCTION OF THE
Abstract:
The cardiovascular system (CVS) and its regulation are highly vulnerable to limited physical activity equally on Earth and in space. Purpose of the work is to study mechanical cardiac reactions to the standing test during extended head-down bed rest (BR) as a function of countermeasures start date. Subjects were 9 male volunteers. To assess the bioelectrical activity of the heart. (ECG) and mechanical activity (echoECG), the standing test was conducted during baseline data collection, every 60 days in BR, and on day 60 of recovery. The results showed a nonlinear dependence of the CVS function on time in BR. Level of orthostatic stability and time for orthostatic stability recovery were largely dependent on the scope of countermeasures applied during BR.
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