Head-up suspension in humans: Effects on sympathetic vasomotor activity and cardiovascular responses

A. S M Shamsuzzaman, Y. Sugiyama, A. Kamiya, Qi Fu, T. Mano

Research output: Contribution to journalArticlepeer-review

25 Scopus citations

Abstract

We hypothesized that muscle sympathetic nerve activity (MSNA) and cardiovascular responses to the conventional head-up tilt (HUT) are different from those to head-up suspension (HUS) because of antigravity muscle activity. The MSNA from the tibial nerve, heart rate, blood pressure, stroke volume, cardiac output, and calf blood flow were measured in 13 healthy young subjects. Left atrial diameter was measured by two-dimensional echocardiography in another nine subjects. The resting MSNA and cardiovascular responses at a low level (20°) of orthostasis were similar during both modes. At higher levels (40 and 60°), the responses of MSNA, heart rate, stroke volume, and cardiac output were significantly stronger and there was a smaller reduction in calf blood flow during HUT than during HUS (P < 0.05). Left atrial diameter was decreased significantly from the resting values during HUT and HUS without any significant difference between the modes of orthostasis. The results provide evidence that the engagement of antigravity muscles during HUT may have additive effects on sympathetic vasoconstrictor and cardiovascular responses to orthostatic stress.

Original languageEnglish (US)
Pages (from-to)1513-1519
Number of pages7
JournalJournal of applied physiology
Volume84
Issue number5
DOIs
StatePublished - May 1998

Keywords

  • Gravity
  • Head-up tilt
  • Microneurography
  • Muscle sympathetic nerve activity
  • Posture

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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