Abstract
Both heat stress and vestibular activation alter autonomic responses; however, the interaction of these two sympathetic activators is unknown. To determine the effect of heat stress on the vestibulosympathetic reflex, eight subjects performed static head-down rotation (HDR) during normothermia and whole body heating. Muscle sympathetic nerve activity (MSNA; peroneal microneurography), mean arterial blood pressure (MAP), heart rate (HR), and internal temperature were measured during the experimental trials. HDR during normothermia caused a significant increase in MSNA (Δ5 ± 1 bursts/min; Δ53 ± 14 arbitrary units/min), whereas no change was observed in MAP, HR, or internal temperature. Whole body heating significantly increased internal temperature (Δ0.9 ± 0.1°C), MSNA (Δ10 ± 3 bursts/min; Δ152 ± 44 arbitrary units/min), and HR (Δ25 ± 6 beats/min), but it did not alter MAP. HDR during whole body heating increased MSNA (Δ16 + 4 bursts/min; Δ233 ± 90 arbitrary units/min from normothermic baseline), which was not significantly different from the algebraic sum of HDR during normothermia and whole body heating (Δ15 ± 4 bursts/min; Δ205 ± 55 arbitrary units/min). These data suggest that heat stress does not modify the vestibulosympathetic reflex and that both the vestibulosympathetic and thermal reflexes are robust, independent sympathetic nervous system activators.
Original language | English |
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Pages (from-to) | 1367-1370 |
Number of pages | 4 |
Journal | Journal of Applied Physiology |
Volume | 97 |
Issue number | 4 |
DOIs | |
State | Published - Oct 2004 |
Keywords
- Heat stress
- Microneurography
- Muscle sympathetic nerve activity
- Orthostasis
- Otolith organs
ASJC Scopus subject areas
- Physiology
- Physiology (medical)