Author:
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.
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·kg−1·min−1 maximal aerobic power) performed four randomized walking trials (90 min, 5.6 km/h, 5% grade) in the heat (33°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 (Posm), plasma vasopressin (PAVP), 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 Posm and PAVP 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.
Publisher
American Physiological Society
Subject
Physiology (medical),Physiology
Reference43 articles.
1. Adolph EF and Willis JH. Thirst. In: Physiology of Man in the Desert, edited by Adolph EF. New York: Interscience, 1947, p. 241–253.
2. ADH in Regulation of Blood Osmolality and Extracellular Fluid Volume
3. Urinary Indices during Dehydration, Exercise, and Rehydration
4. Thermal and circulatory responses during exercise: effects of hypohydration, dehydration, and water intake
5. Boudou P, Fiet J, Laureaux C, Patricot MC, Guezennec CY, Foglietti MJ, Villette JM, Friemel F, and Haag JC. Changes in several plasma and urinary components in marathon runners. Ann Biol Clin (Paris) 45: 37–45, 1987.
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