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Updated: Aug 13, 2026
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Tilt Testing with Combined Lower Body Negative Pressure: a "Gold Standard" for Measuring Orthostatic Tolerance
Published on: March 21, 2013
Orthostatic intolerance: emerging genetic and environmental etiologies
D Robertson1, I Biaggioni, A C Ertl
1Center for Space Physiology and Medicine, Vanderbilt University, Nashville, TN 37232, USA.
Journal of Gravitational Physiology : a Journal of the International Society for Gravitational Physiology
|September 7, 2001
Summary
Orthostatic intolerance after spaceflight is linked to increased sympathetic nervous system activity, not reduced activity. This finding helps understand astronaut adaptation and related conditions on Earth.
Area of Science:
- Space Physiology
- Autonomic Neuroscience
- Cardiovascular Adaptation
Background:
- Orthostatic intolerance (OI) is common post-spaceflight and in idiopathic cases.
- OI can result from either reduced or increased sympathetic nervous system activity.
- Microgravity alters cardiovascular and autonomic control, leading to OI upon return to gravity.
Purpose of the Study:
- To determine if astronaut OI post-spaceflight is hypoadrenergic or hyperadrenergic.
- To investigate autonomic nervous system adaptations during spaceflight.
Main Methods:
- Analysis of plasma catecholamines during spaceflight.
- Assessment of peroneal microneurographic sympathetic nerve traffic.
- Measurement of norepinephrine spillover and clearance using tritiated norepinephrine infusion.
Main Results:
- A slight increase in muscle sympathetic nerve activity was observed.
- Plasma norepinephrine levels and norepinephrine clearance were elevated.
- Enhanced sympathetic activation accompanied orthostatic intolerance post-microgravity.
Conclusions:
- Orthostatic intolerance following microgravity is associated with enhanced sympathetic activation.
- Findings provide insight into autonomic dysfunction after space travel.
- Understanding these mechanisms is crucial for both astronaut health and terrestrial OI patients.
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