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Rehydration with fluid of varying tonicities: effects on fluid regulatory hormones and exercise performance in the heat.
J Appl Physiol (1985). 2007 May; 102(5):1899-905.JA

Abstract

This study examined the effects of rehydration (Rehy) with fluids of varying tonicities and routes of administration after exercise-induced hypohydration on exercise performance, fluid regulatory hormone responses, and cardiovascular and thermoregulatory strain during subsequent exercise in the heat. On four occasions, eight men performed an exercise-dehydration protocol of approximately 185 min (33 degrees C) to establish a 4% reduction in body weight. Following dehydration, 2% of the fluid lost was replaced during the first 45 min of a 100-min rest period by one of three random Rehy treatments (0.9% saline intravenous; 0.45% saline intravenous; 0.45% saline oral) or no Rehy (no fluid) treatment. Subjects then stood for 20 min at 36 degrees C and then walked at 50% maximal oxygen consumption for 90 min. Subsequent to dehydration, plasma Na(+), osmolality, aldosterone, and arginine vasopressin concentrations were elevated (P < 0.05) in each trial, accompanied by a -4% hemoconcentration. Following Rehy, there were no differences (P > 0.05) in fluid volume restored, post-rehydration (Post-Rehy) body weight, or urine volume. Percent change in plasma volume was 5% above pre-Rehy values, and plasma Na(+), osmolality, and fluid regulatory hormones were lower compared with no fluid. During exercise, skin and core temperatures, heart rate, and exercise time were not different (P > 0.05) among the Rehy treatments. Plasma osmolality, Na(+), percent change in plasma volume, and fluid regulatory hormones responded similarly among all Rehy treatments. Neither a fluid of greater tonicity nor the route of administration resulted in a more rapid or greater fluid retention, nor did it enhance heat tolerance or diminish physiological strain during subsequent exercise in the heat.

Authors+Show Affiliations

US Army Research Institute of Environmental Medicine, Thermal and Mountain Medicine Division, Natick, MA 01760, USA. Robert.Kenefick@us.army.milNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

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

Language

eng

PubMed ID

17317877

Citation

Kenefick, R W., et al. "Rehydration With Fluid of Varying Tonicities: Effects On Fluid Regulatory Hormones and Exercise Performance in the Heat." Journal of Applied Physiology (Bethesda, Md. : 1985), vol. 102, no. 5, 2007, pp. 1899-905.
Kenefick RW, Maresh CM, Armstrong LE, et al. Rehydration with fluid of varying tonicities: effects on fluid regulatory hormones and exercise performance in the heat. J Appl Physiol. 2007;102(5):1899-905.
Kenefick, R. W., Maresh, C. M., Armstrong, L. E., Riebe, D., Echegaray, M. E., & Castellani, J. W. (2007). Rehydration with fluid of varying tonicities: effects on fluid regulatory hormones and exercise performance in the heat. Journal of Applied Physiology (Bethesda, Md. : 1985), 102(5), 1899-905.
Kenefick RW, et al. Rehydration With Fluid of Varying Tonicities: Effects On Fluid Regulatory Hormones and Exercise Performance in the Heat. J Appl Physiol. 2007;102(5):1899-905. PubMed PMID: 17317877.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Rehydration with fluid of varying tonicities: effects on fluid regulatory hormones and exercise performance in the heat. AU - Kenefick,R W, AU - Maresh,C M, AU - Armstrong,L E, AU - Riebe,D, AU - Echegaray,M E, AU - Castellani,J W, Y1 - 2007/02/22/ PY - 2007/2/24/pubmed PY - 2007/7/14/medline PY - 2007/2/24/entrez SP - 1899 EP - 905 JF - Journal of applied physiology (Bethesda, Md. : 1985) JO - J. Appl. Physiol. VL - 102 IS - 5 N2 - This study examined the effects of rehydration (Rehy) with fluids of varying tonicities and routes of administration after exercise-induced hypohydration on exercise performance, fluid regulatory hormone responses, and cardiovascular and thermoregulatory strain during subsequent exercise in the heat. On four occasions, eight men performed an exercise-dehydration protocol of approximately 185 min (33 degrees C) to establish a 4% reduction in body weight. Following dehydration, 2% of the fluid lost was replaced during the first 45 min of a 100-min rest period by one of three random Rehy treatments (0.9% saline intravenous; 0.45% saline intravenous; 0.45% saline oral) or no Rehy (no fluid) treatment. Subjects then stood for 20 min at 36 degrees C and then walked at 50% maximal oxygen consumption for 90 min. Subsequent to dehydration, plasma Na(+), osmolality, aldosterone, and arginine vasopressin concentrations were elevated (P < 0.05) in each trial, accompanied by a -4% hemoconcentration. Following Rehy, there were no differences (P > 0.05) in fluid volume restored, post-rehydration (Post-Rehy) body weight, or urine volume. Percent change in plasma volume was 5% above pre-Rehy values, and plasma Na(+), osmolality, and fluid regulatory hormones were lower compared with no fluid. During exercise, skin and core temperatures, heart rate, and exercise time were not different (P > 0.05) among the Rehy treatments. Plasma osmolality, Na(+), percent change in plasma volume, and fluid regulatory hormones responded similarly among all Rehy treatments. Neither a fluid of greater tonicity nor the route of administration resulted in a more rapid or greater fluid retention, nor did it enhance heat tolerance or diminish physiological strain during subsequent exercise in the heat. SN - 8750-7587 UR - https://www.unboundmedicine.com/medline/citation/17317877/Rehydration_with_fluid_of_varying_tonicities:_effects_on_fluid_regulatory_hormones_and_exercise_performance_in_the_heat_ L2 - http://www.physiology.org/doi/full/10.1152/japplphysiol.00920.2006?url_ver=Z39.88-2003&amp;rfr_id=ori:rid:crossref.org&amp;rfr_dat=cr_pub=pubmed DB - PRIME DP - Unbound Medicine ER -