Document Detail

Fitness alters fluid regulatory but not behavioural responses to hypohydrated exercise.
MedLine Citation:
PMID:  18644399     Owner:  NLM     Status:  MEDLINE    
Dehydration is typical during prolonged exercise. Because training stimulates numerous adaptations, some involving fluid regulation, it is conceivable that training involves adaptations to dehydration. This study tested the hypothesis that trained individuals have altered fluid regulatory, but not behavioural or perceptual responses to exercise when hypohydrated. Six trained (V.O2 peak: 65+/-8 mL kg(-1) min(-1)) and six untrained (V.O2 peak: 45+/-4 mL kg(-1) min(-1)) males cycled for 40 min at 70%V.O2 peak, once whilst euhydrated (EUH) and once whilst hypohydrated by ~2% body mass (HYPO), before a 40-min performance trial with euhydration (in EUH) or ad libitum drinking (in HYPO), in temperate conditions (24.3 degrees C, 50% rh). Baseline hydration was achieved by complete or partial rehydration from exercise+heat stress on the previous evening. Body mass was reduced (-1.8+/-0.1%) and plasma osmolality was increased (5+/-1 mosmol kg(-1)) similarly between fitness groups in HYPO compared to EUH (P<0.05). During exercise, plasma [AVP] rose more in HYPO than EUH; the elevation was greater in the Untrained (4.1+/-1.7 vs. 2.0+/-0.8 pmol L(-1), P<0.01) than Trained (1.4+/-0.6 vs. 1.1+/-0.5 pmol L(-1), P<0.01; P=0.02). Increases in plasma [AVP] relative to osmolality were higher in Untrained than Trained (0.47+/-0.06 vs. 0.025+/-0.05 pmol mosmol(-1), P=0.03). Fitness groups had equivalent thirst ratings during fixed exercise but Trained were thirstier than Untrained when self regulating in HYPO (4.0+/-1.5 vs. 2.7+/-1.2; P=0.05); thus Trained tended to consume more fluid (1.20+/-0.16 vs. 0.88+/-0.16 L; P=0.19), but maintained similar hypohydration consistent with their greater sweat rate during HYPO. In conclusion, aerobic fitness attenuates the neuroendocrine ([AVP]) response to hypohydrated exercise, but not perceptual (thirst) or behavioural (ad libitum drinking) responses.
Troy L Merry; Philip N Ainslie; Robert Walker; James D Cotter
Related Documents :
17918699 - Ultrasound heating is curvilinear in nature and varies between transducers from the sam...
3356849 - Control of house dust mites by electrical heating blankets.
2690809 - Plasma renin activity and aldosterone: correlations with moderate hypohydration.
1761469 - Aldosterone and prolactin response to exercise in the heat in circumpubertal boys.
24531429 - The role of self-reported individual differences in preference for and tolerance of exe...
3355239 - Role of dehydration in heat stress-induced variations in mental performance.
3922029 - Measurement of mixed venous carbon dioxide pressure by rebreathing during exercise.
22247299 - Airway dysfunction in swimmers.
24905559 - Running sprint interval training induces fat loss in women.
Publication Detail:
Type:  Journal Article; Randomized Controlled Trial; Research Support, Non-U.S. Gov't     Date:  2008-07-02
Journal Detail:
Title:  Physiology & behavior     Volume:  95     ISSN:  0031-9384     ISO Abbreviation:  Physiol. Behav.     Publication Date:  2008 Oct 
Date Detail:
Created Date:  2008-10-17     Completed Date:  2009-02-03     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0151504     Medline TA:  Physiol Behav     Country:  United States    
Other Details:
Languages:  eng     Pagination:  348-52     Citation Subset:  IM    
School of Physical Education, University of Otago, Dunedin, New Zealand.
Export Citation:
APA/MLA Format     Download EndNote     Download BibTex
MeSH Terms
Analysis of Variance
Arginine Vasopressin / blood
Body Fluids / physiology*
Cross-Over Studies
Dehydration / metabolism*,  physiopathology*
Hemoglobins / metabolism
Osmolar Concentration
Oxygen Consumption
Physical Fitness*
Sodium / blood
Thirst / physiology
Reg. No./Substance:
0/Hemoglobins; 113-79-1/Arginine Vasopressin; 7440-23-5/Sodium

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

Previous Document:  omega-Conotoxin inhibition of excitatory synaptic transmission evoked by dorsal root stimulation in ...
Next Document:  Side-chain modified vitamin D analogs induce rapid accumulation of VDR in the cell nuclei proportion...