Human muscle sympathetic neural and haemodynamic responses to tilt following spaceflight
Open accessAbstract
Orthostatic intolerance is common when astronauts return to Earth: after brief spaceflight, up to two‐thirds are unable to remain standing for 10 min. Previous research suggests that susceptible individuals are unable to increase their systemic vascular resistance and plasma noradrenaline concentrations above pre‐flight upright levels. In this study, we tested the hypothesis that adaptation to the microgravity of space impairs sympathetic neural responses to upright posture on Earth. We studied six astronauts ∼72 and 23 days before and on landing day after the 16 day Neurolab space shuttle mission. We measured heart rate, arterial pressure and cardiac output, and calculated stroke volume and total peripheral resistance, during supine rest and 10 min of 60 deg upright tilt. Muscle sympathetic nerve activity was recorded in five subjects, as a direct measure of sympathetic nervous system responses. As in previous studies, mean (±s.e.m.) stroke volume was lower (46 ± 5 vs. 76 ± 3 ml, P= 0.017) and heart rate was higher (93 ± 1 vs. 74 ± 4 beats min−1, P= 0.002) during tilt after spaceflight than before spaceflight. Total peripheral resistance during tilt post flight was higher in some, but not all astronauts (1674 ± 256 vs. 1372 ± 62 dynes s cm−5, P= 0.32). No crew member exhibited orthostatic hypotension or presyncopal symptoms during the 10 min of postflight tilting. Muscle sympathetic nerve activity was higher post flight in all subjects, in supine (27 ± 4 vs. 17 ± 2 bursts min−1, P= 0.04) and tilted (46 ± 4 vs. 38 ± 3 bursts min−1, P= 0.01) positions. A strong (r2= 0.91–1.00) linear correlation between left ventricular stroke volume and muscle sympathetic nerve activity suggested that sympathetic responses were appropriate for the haemodynamic challenge of upright tilt and were unaffected by spaceflight. We conclude that after 16 days of spaceflight, muscle sympathetic nerve responses to upright tilt are normal.
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Postflight orthostatic intolerance on return to Earth has been noted following both short- and long-term flights, especially in women astronauts.
“Since the inception of space missions, a postflight orthostatic intolerance on return to Earth has been noted following both short-and long-term flights, especially in women astronauts.”
From Postural Orthostatic Tachycardia Syndrome (2019) · cites this paper as [18]
The Discussion states that orthostatic intolerance has been observed after both short- and long-duration missions since the inception of the manned space program. It does not say it occurs especially in women; the Methods (Subjects) report that this study included only six male crew members. No page number is available for these passages. (LLM, conf=0.90)
Experimental — accuracy not yet measuredMany studies have demonstrated that prolonged bedrest or microgravity exposure can result in a POTS-like syndrome characterized by a tachycardic orthostatic intolerance even in previously healthy and active individuals.
“Many studies have demonstrated that prolonged bedrest or microgravity exposure can result in a POTS-like syndrome characterized by a tachycardic orthostatic intolerance even in previously healthy and active individuals (17,18,25,27,57-60).”
From Postural Orthostatic Tachycardia Syndrome (2019) · cites this paper as [18]
The Discussion (page not provided) reports greater tachycardia after spaceflight and describes earlier studies in which astronauts could not remain standing for 10 minutes. It also notes increased heart rates after head-down bed rest, but does not establish bed-rest-induced orthostatic intolerance or characterize the response as a POTS-like syndrome in previously healthy, active individuals. None of this study’s astronauts experienced presyncope during postflight tilt. (LLM, conf=0.85)
Experimental — accuracy not yet measuredEven after brief space trips, approximately one-fourth to two-thirds of astronauts cannot stand for even 10 min upon return to Earth.
“Even after brief trips, approximately one-fourth to two-thirds of astronauts cannot stand for even 10 min upon return to earth (16)(17)(18).”
From Postural Orthostatic Tachycardia Syndrome (2019) · cites this paper as [18]
In six previously healthy male astronauts, just 16 days of spaceflight resulted in a decrease in blood volume of nearly 6%.
“Levine et al. (39) demonstrated that in six previously healthy male astronauts, just 16 days of spaceflight resulted in a decrease in blood volume of nearly 6% (39).”
From Postural orthostatic tachycardia syndrome: mechanisms and new therapies (2020) · cites this paper as [39]
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References 58 · Cited by 191
Research works printed but not linked: 2
- Blomqvist CG, Levine BD, Lane LD. Evaluating cardiac patients at special risk: noncardiac surgery and occupational, environmental, and recreational considerations. In: Brunwald E, Crawford MH, editors. Atlas of Heart Diseases, Heart Disease in the Presence of Disorders of other Organ Systems. Vol. 6. Philadelphia, PA, USA: Mosby; 1996. pp. 10.1–10.29. [Google Scholar]
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- Authors
- Levine, B. D., Pawelczyk, J. A., Ertl, A. C., Cox, J. F., Zuckerman, J. H., Diedrich, A., Biaggioni, I., Ray, C. A., Smith, M. L., Iwase, S., Saito, M., Sugiyama, Y., Mano, T., Zhang, R., Iwasaki, K., Lane, L. D., Buckey, J. C., Cooke, W. H., Baisch, F. J., Robertson, D., Eckberg, D. L., & Blomqvist, C. G.
- Affiliations
- Texas Health Dallas (US)
- Pennsylvania State University (US)
- Virginia Commonwealth University (US)
- Vanderbilt University (US)
- University of North Texas (US)
- Research Institute of Environmental Medicine, Nagoya University (JP)
- Dartmouth–Hitchcock Medical Center (US)
- Michigan Technological University (US)
- Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR) (DE)
- Corresponding author
- Levine, Benjamin D.
- ORCID
- Venue
- The Journal of Physiology
- Publisher
- Wiley
- Published
- 2002-01
- Volume
- 538
- Issue
- 1
- Pages
- 331-340
- ISSN
- 0022-3751 (ISSN-L)
- 1469-7793
- PMC
- PMC2290017
- OpenAlex
- W2018638227
- Cited by
- 191
- References
- 58
- Citations by year
- 2026: 3 · 2025: 6 · 2024: 8 · 2023: 8 · 2022: 6 · 2021: 5 · 2020: 5 · 2019: 7 · 2018: 6 · 2017: 4 · 2016: 7 · 2015: 6 · 2014: 6 · 2013: 6 · 2012: 5
- FWCI
- 8.59
- Type
- journal article
- Language
- en
- Open access
- green
- www.ncbi.nlm.nih.gov
- Locations
- The Journal of Physiology (publishedVersion)
- PubMed Central (publishedVersion)
- PubMed (publishedVersion)
- Digital Commons - Michigan Tech (Michigan Technological University) (submittedVersion)
- Funders
- National Aeronautics and Space Administration
- Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
- Topics
- Health Sciences › Medicine › Physiology › Spaceflight effects on biology
- Health Sciences › Medicine › Surgery › Cardiovascular Syncope and Autonomic Disorders
- Health Sciences › Medicine › Cardiology and Cardiovascular Medicine › Heart Rate Variability and Autonomic Control
- Keywords
- spaceflight, orthostatic intolerance, muscle sympathetic nerve activity, upright tilt, hemodynamics, stroke volume, systemic vascular resistance, heart rate, cardiac output, microgravity adaptation, astronauts, sympathetic nervous system
- MeSH terms
- Adult, Hemodynamics, Humans, Male, Space Flight, Sympathetic Nervous System, Supine Position, Head-Down Tilt, Astronauts, Muscle, Skeletal
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