Muscle sympathetic nerve activity during lower body negative pressure is accentuated in heat-stressed humans

Jian Cui, Thad E. Wilson, Craig G. Crandall

Research output: Contribution to journalArticle

39 Scopus citations

Abstract

The purpose of this project was to test the hypothesis that increases in muscle sympathetic nerve activity (MSNA) during an orthostatic challenge is attenuated in heat-stressed individuals. To accomplish this objective, MSNA was measured during graded lower body negative pressure (LBNP) in nine subjects under normothermic and heat-stressed conditions. Progressive LBNP was applied at -3, -6, -9, -12, -15, -18, -21, and -40 mmHg for 2 min per stage. Whole body heating caused significant increases in sublingual temperature, skin blood flow, sweat rate, heart rate, and MSNA (all P < 0.05) but not in mean arterial blood pressure (P > 0.05). Progressive LBNP induced significant increases in MSNA in both thermal conditions. However, during the heat stress trial, increases in MSNA at LBNP levels higher than -9 mmHg were greater compared with during the same LBNP levels in normothermia (all P < 0.05). These data suggest that the increase in MSNA to orthostatic stress is not attenuated but rather accentuated in heat-stressed humans.

Original languageEnglish (US)
Pages (from-to)2103-2108
Number of pages6
JournalJournal of applied physiology
Volume96
Issue number6
DOIs
StatePublished - Jun 1 2004

Keywords

  • Autonomic nervous system
  • Baroreflexes
  • Hyperthermia
  • Orthostasis
  • Vasomotor

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)

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