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effects of heat stress on baroreflex function in humansINTRODUCTION: Heat stress significantly reduces orthostatic tolerance in humans. The mechanism(s) causing this response remain unknown. The purpose of this review article is to present data pertaining to the hypothesis that reduced orthostatic tolerance in heat stressed individuals is a result of heat stress induced alterations in baroflex function. METHODS: In both normothermic and heat stressed conditions baroreflex responsiveness was assessed via pharmacological and non-pharmacological methods. In addition, the effects of heat stress on post-synaptic vasoconstrictor responsiveness were assessed. RESULTS: Generally, whole body heating did not alter baroreflex sensitivity defined as the gain of the linear portion of the baroreflex curve around the operating point. However, whole body heating shifted the baroreflex curve to the prevailing (i.e. elevated) heart rate and muscle sympathetic nerve activity. Finally, the heat stress impaired vasoconstrictor responses to exogenous administration of adrenergic agonists. CONCLUSION: Current data do not support the hypothesis that reduced orthostatic tolerance associated with heat stress in humans is due to impaired baroreflex responsiveness. This phenomenon may be partially due to the effects of heat stress on reducing vasoconstrictor responsiveness.
Document ID
20040087815
Document Type
Reprint (Version printed in journal)
Authors
Crandall, Craig G.
(Institute for Excercise and Environmental Medicine, Presbyterian Hospital of Dallas TX 75231, United States)
Cui, Jian
Wilson, Thad E.
Date Acquired
August 21, 2013
Publication Date
March 1, 2003
Publication Information
Publication: Acta physiologica Scandinavica
Volume: 177
Issue: 3
ISSN: 0001-6772
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: HL-67422
CONTRACT_GRANT: HL-10488
CONTRACT_GRANT: HL-61388
Distribution Limits
Public
Copyright
Other
Keywords
Review, Tutorial
Review
Non-NASA Center
NASA Discipline Cardiopulmonary