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Effect of hydration status on thirst, drinking, and related hormonal responses during low-intensity exercise in the heat.
J Appl Physiol (1985). 2004 Jul; 97(1):39-44.JA

Abstract

During exercise-heat stress, ad libitum drinking frequently fails to match sweat output, resulting in deleterious changes in hormonal, circulatory, thermoregulatory, and psychological status. This condition, known as voluntary dehydration, is largely based on perceived thirst. To examine the role of preexercise dehydration on thirst and drinking during exercise-heat stress, 10 healthy men (21 +/- 1 yr, 57 +/- 1 ml x kg(-1) x min(-1) maximal aerobic power) performed four randomized walking trials (90 min, 5.6 km/h, 5% grade) in the heat (33 degrees C, 56% relative humidity). Trials differed in preexercise hydration status [euhydrated (Eu) or hypohydrated to -3.8 +/- 0.2% baseline body weight (Hy)] and water intake during exercise [no water (NW) or water ad libitum (W)]. Blood samples taken preexercise and immediately postexercise were analyzed for hematocrit, hemoglobin, serum aldosterone, plasma osmolality (P(osm)), plasma vasopressin (P(AVP)), and plasma renin activity (PRA). Thirst was evaluated at similar times using a subjective nine-point scale. Subjects were thirstier before (6.65 +/- 0.65) and drank more during Hy+W (1.65 +/- 0.18 liters) than Eu+W (1.59 +/- 0.41 and 0.31 +/- 0.11 liters, respectively). Postexercise measures of P(osm) and P(AVP) were significantly greater during Hy+NW and plasma volume lower [Hy+NW = -5.5 +/- 1.4% vs. Hy+W = +1.0 +/- 2.5% (P = 0.059), Eu+NW = -0.7 +/- 0.6% (P < 0.05), Eu+W = +0.5 +/- 1.6% (P < 0.05)] than all other trials. Except for thirst and drinking, however, no Hy+W values differed from Eu+NW or Eu+W values. In conclusion, dehydration preceding low-intensity exercise in the heat magnifies thirst-driven drinking during exercise-heat stress. Such changes result in similar fluid regulatory hormonal responses and comparable modifications in plasma volume regardless of preexercise hydration state.

Authors+Show Affiliations

Department of Kinesiology, University of Connecticut, Storrs, CT 06269-1110, USA. carl.maresh@uconn.eduNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Clinical Trial
Journal Article
Randomized Controlled Trial
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

14990557

Citation

Maresh, C M., et al. "Effect of Hydration Status On Thirst, Drinking, and Related Hormonal Responses During Low-intensity Exercise in the Heat." Journal of Applied Physiology (Bethesda, Md. : 1985), vol. 97, no. 1, 2004, pp. 39-44.
Maresh CM, Gabaree-Boulant CL, Armstrong LE, et al. Effect of hydration status on thirst, drinking, and related hormonal responses during low-intensity exercise in the heat. J Appl Physiol. 2004;97(1):39-44.
Maresh, C. M., Gabaree-Boulant, C. L., Armstrong, L. E., Judelson, D. A., Hoffman, J. R., Castellani, J. W., Kenefick, R. W., Bergeron, M. F., & Casa, D. J. (2004). Effect of hydration status on thirst, drinking, and related hormonal responses during low-intensity exercise in the heat. Journal of Applied Physiology (Bethesda, Md. : 1985), 97(1), 39-44.
Maresh CM, et al. Effect of Hydration Status On Thirst, Drinking, and Related Hormonal Responses During Low-intensity Exercise in the Heat. J Appl Physiol. 2004;97(1):39-44. PubMed PMID: 14990557.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Effect of hydration status on thirst, drinking, and related hormonal responses during low-intensity exercise in the heat. AU - Maresh,C M, AU - Gabaree-Boulant,C L, AU - Armstrong,L E, AU - Judelson,D A, AU - Hoffman,J R, AU - Castellani,J W, AU - Kenefick,R W, AU - Bergeron,M F, AU - Casa,D J, Y1 - 2004/02/27/ PY - 2004/3/3/pubmed PY - 2004/12/21/medline PY - 2004/3/3/entrez SP - 39 EP - 44 JF - Journal of applied physiology (Bethesda, Md. : 1985) JO - J. Appl. Physiol. VL - 97 IS - 1 N2 - During exercise-heat stress, ad libitum drinking frequently fails to match sweat output, resulting in deleterious changes in hormonal, circulatory, thermoregulatory, and psychological status. This condition, known as voluntary dehydration, is largely based on perceived thirst. To examine the role of preexercise dehydration on thirst and drinking during exercise-heat stress, 10 healthy men (21 +/- 1 yr, 57 +/- 1 ml x kg(-1) x min(-1) maximal aerobic power) performed four randomized walking trials (90 min, 5.6 km/h, 5% grade) in the heat (33 degrees C, 56% relative humidity). Trials differed in preexercise hydration status [euhydrated (Eu) or hypohydrated to -3.8 +/- 0.2% baseline body weight (Hy)] and water intake during exercise [no water (NW) or water ad libitum (W)]. Blood samples taken preexercise and immediately postexercise were analyzed for hematocrit, hemoglobin, serum aldosterone, plasma osmolality (P(osm)), plasma vasopressin (P(AVP)), and plasma renin activity (PRA). Thirst was evaluated at similar times using a subjective nine-point scale. Subjects were thirstier before (6.65 +/- 0.65) and drank more during Hy+W (1.65 +/- 0.18 liters) than Eu+W (1.59 +/- 0.41 and 0.31 +/- 0.11 liters, respectively). Postexercise measures of P(osm) and P(AVP) were significantly greater during Hy+NW and plasma volume lower [Hy+NW = -5.5 +/- 1.4% vs. Hy+W = +1.0 +/- 2.5% (P = 0.059), Eu+NW = -0.7 +/- 0.6% (P < 0.05), Eu+W = +0.5 +/- 1.6% (P < 0.05)] than all other trials. Except for thirst and drinking, however, no Hy+W values differed from Eu+NW or Eu+W values. In conclusion, dehydration preceding low-intensity exercise in the heat magnifies thirst-driven drinking during exercise-heat stress. Such changes result in similar fluid regulatory hormonal responses and comparable modifications in plasma volume regardless of preexercise hydration state. SN - 8750-7587 UR - https://www.unboundmedicine.com/medline/citation/14990557/Effect_of_hydration_status_on_thirst_drinking_and_related_hormonal_responses_during_low_intensity_exercise_in_the_heat_ L2 - http://www.physiology.org/doi/full/10.1152/japplphysiol.00956.2003?url_ver=Z39.88-2003&amp;rfr_id=ori:rid:crossref.org&amp;rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -