Document Detail

The impact of heat exposure and repeated exercise on circulating stress hormones.
MedLine Citation:
PMID:  9367285     Owner:  NLM     Status:  MEDLINE    
To determine if heat exposure alters the hormonal responses to moderate, repeated exercise, 11 healthy male subjects [age = 27.1 (3.0) years; maximal oxygen consumption, VO2max = 47.6 (6.2) ml x kg x min(-1); mean (SD)] were assigned to four different experimental conditions according to a randomized-block design. While in a thermoneutral (23 degrees C) or heated (40 degrees C, 30% relative humidity) climatic chamber, subjects performed either cycle ergometer exercise (two 30-min bouts at approximately 50% VO2max, separated by a 45-min recovery interval, CEx and HEx conditions), or remained seated for 3 h (CS and HS conditions). Blood samples were analyzed for various exercise stress hormones [epinephrine (E), norepinephrine (NE), dopamine, cortisol and human growth hormone (hGH)]. Passive heating did not alter the concentrations of any of these hormones significantly. During both environmental conditions, exercise induced significant (P < 0.001) elevations in plasma E, NE and hGH levels. At 23 degrees C during bout 1: E = 393 (199) pmol x l(-1) (CEx) vs 174 (85) pmol x l(-1) (CS), NE = 4593 (2640) pmol x l(-1) (CEx) vs 1548 (505) pmol x l(-1) (CS), and hGH = 274 (340) pmol x l(-1) (CEx)vs 64 (112) pmol x l(-1) (CS). At 40 degrees C, bout 1: E = 596 (346) pmol x l(-1) (HEx) vs 323 (181) pmol x l(-1) (HS), NE = 7789 (5129) pmol x l(-1) (HEx) vs 1527 (605) pmol x l(-1) (HS), and hGH = 453 (494) pmol x l(-1) (HEx) vs 172 (355) pmol x l(-1) (HS). However, concentrations of plasma cortisol were increased only in response to exercise in the heat [HEx = 364 (168) nmol x l(-1) vs HS = 295 (114) nmol x l(-1)]. Compared to exercise at room temperature, plasma levels of E, NE and cortisol were all higher during exercise in the heat (P < 0.001 in all cases). The repetition of exercise did not significantly alter the pattern of change in cortisol or hGH levels in either environmental condition. However, repetition of exercise in the heat increased circulatory and psychological stress, with significantly (P < 0.001) higher plasma concentrations of E and NE. These results indicate a differential response of the various stress hormones to heat exposure and repeated moderate exercise.
I K Brenner; J Zamecnik; P N Shek; R J Shephard
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Publication Detail:
Type:  Clinical Trial; Journal Article; Randomized Controlled Trial; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  European journal of applied physiology and occupational physiology     Volume:  76     ISSN:  0301-5548     ISO Abbreviation:  Eur J Appl Physiol Occup Physiol     Publication Date:  1997  
Date Detail:
Created Date:  1997-12-22     Completed Date:  1997-12-22     Revised Date:  2008-11-21    
Medline Journal Info:
Nlm Unique ID:  0410266     Medline TA:  Eur J Appl Physiol Occup Physiol     Country:  GERMANY    
Other Details:
Languages:  eng     Pagination:  445-54     Citation Subset:  IM    
Graduate Department of Community Health, University of Toronto, Ontario, Canada.
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MeSH Terms
Body Temperature / physiology
Dopamine / blood
Epinephrine / blood
Exercise / physiology*
Exercise Test
Growth Hormone / blood
Hormones / blood*
Hot Temperature / adverse effects*
Hydrocortisone / blood
Norepinephrine / blood
Oxygen Consumption / physiology
Stress, Physiological / blood*
Reg. No./Substance:
0/Hormones; 50-23-7/Hydrocortisone; 51-41-2/Norepinephrine; 51-43-4/Epinephrine; 9002-72-6/Growth Hormone

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