Nine months in space: Effects on human autonomic cardiovascular regulation

William H. Cooke, James E. Ames IV, Alexandra A. Crossman, James F. Cox, Tom A. Kuusela, Kari U O Tahvanainen, L. Boyce Moon, Jürgen Drescher, Friedhelm J. Baisch, Tadaaki Mano, Benjamin D. Levine, C. Gunnar Blomqvist, Dwain L. Eckberg

Research output: Contribution to journalArticlepeer-review

85 Scopus citations


We studied three Russian cosmonauts to better understand how long-term exposure to microgravity affects autonomic cardiovascular control. We recorded the electrocardiogram, finger photoplethysmographic pressure, and respiratory flow before, during, and after two 9-mo missions to the Russian space station Mir. Measurements were made during four modes of breathing: 1) uncontrolled spontaneous breathing; 2) stepwise breathing at six different frequencies; 3) fixed-frequency breathing; and 4) random-frequency breathing. R wave-to-R wave (R-R) interval standard deviations decreased in all and respiratory frequency R-R interval spectral power decreased in two cosmonauts in space. Two weeks after the cosmonauts returned to Earth, R-R interval spectral power was decreased, and systolic pressure spectral power was increased in all. The transfer function between systolic pressures and R-R intervals was reduced in-flight, was reduced further the day after landing, and had not returned to preflight levels by 14 days after landing. Our results suggest that long-duration spaceflight reduces vagal-cardiac nerve traffic and decreases vagal baroreflex gain and that these changes may persist as long as 2 wk after return to Earth.

Original languageEnglish (US)
Pages (from-to)1039-1045
Number of pages7
JournalJournal of applied physiology
Issue number3
StatePublished - 2000


  • Baroreflex
  • Cardiac control
  • Space station Mir

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)


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