Document Detail

Menstrual cycle and sex affect hemodynamic responses to combined orthostatic and heat stress.
MedLine Citation:
PMID:  15778279     Owner:  NLM     Status:  MEDLINE    
Women have decreased orthostatic tolerance compared with men, and anecdotal evidence suggests women are more susceptible to orthostatic intolerance in warm environments. Because estrogen and progesterone affect numerous physiological variables that may alter orthostatic tolerance, the purpose of our study was to compare orthostatic tolerance across the menstrual cycle phases in women during combined orthostatic and heat stress and to compare these data with those of men. Eight normally menstruating women and eight males (22 +/- 4.0 and 23 +/- 3.5 yr, respectively) completed the protocol. Women were studied during their early follicular (EF), ovulatory (OV), and midluteal (ML) phases. Men were studied twice within 2-4 wk. Heart rate, cardiac output, blood pressure, core temperature (T(c)), and cutaneous vascular conductance (CVC) were measured during three head-up tilt tests, consisting of two tilts in the thermoneutral condition and one tilt after a 0.5 degrees C rise in T(c). There was no difference in orthostatic tolerance across the menstrual cycle phases, despite higher CVC in the ML phase after heating (EF, 42.3 +/- 4.8; OV, 40.1 +/- 3.7; ML, 57.5 +/- 4.5; P < 0.05). Orthostatic tolerance in the heat was greater in men than women (P < 0.05). These data suggest that although many physiological variables associated with blood pressure regulation fluctuate during the menstrual cycle, orthostatic tolerance in the heat remains unchanged. Additionally, our data support a clear sex difference in orthostatic tolerance and extend upon previous data to show that the sex difference in the heat is not attributable to fluctuating hormone profiles during the menstrual cycle.
Jessica R Meendering; Britta N Torgrimson; Belinda L Houghton; John R Halliwill; Christopher T Minson
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2005-03-18
Journal Detail:
Title:  American journal of physiology. Heart and circulatory physiology     Volume:  289     ISSN:  0363-6135     ISO Abbreviation:  Am. J. Physiol. Heart Circ. Physiol.     Publication Date:  2005 Aug 
Date Detail:
Created Date:  2005-07-14     Completed Date:  2005-09-08     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  100901228     Medline TA:  Am J Physiol Heart Circ Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  H631-42     Citation Subset:  IM    
Department of Human Physiology, University of Oregon, 1240 Univ. of Oregon, Eugene, OR 97403, USA.
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MeSH Terms
Dizziness / complications*,  physiopathology*
Heat Stress Disorders / complications*,  physiopathology*
Hot Temperature
Menstrual Cycle*
Sex Characteristics*
Syncope / etiology
Tilt-Table Test
Time Factors

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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