Hydration effects on physiological strain of horses during exercise-heat stress.
Abstract: This study examined the effects of hyperhydration, exercise-induced dehydration, and oral fluid replacement on physiological strain of horses during exercise-heat stress. On three occasions, six horses completed a 90-min exercise protocol (50% maximal O2 uptake, 34.5 degrees C, 48% relative humidity) divided into two 45-min periods (exercise I and exercise II) with a 15-min recovery between exercise bouts. In random order, horses received no fluid (NF), 10 liters of water (W), or a carbohydrate-electrolyte solution (CE) 2 h before exercise and between exercise bouts. Compared with NF, preexercise hyperhydration (W and CE) did not alter heart rate, cardiac output (Q), stroke volume (SV), core body temperature, sweating rate (SR), or sweating sensitivity during exercise I. In contrast, after exercise II, exercise-induced dehydration in NF (decrease in body mass: NF, 5.6 +/- 0.8%; W, 1.1 +/- 0.4%; CE, 1.0 +/- 0.2%) resulted in greater heat storage, with core body temperature approximately 1. 0 degrees C higher compared with W and CE. In exercise II, the greater thermal strain in NF was associated with significant (P < 0. 05) decreases in Q (10 +/- 2%), SV (9 +/- 3%), SR, and sweating sensitivity. We concluded that 1) preexercise hyperhydration provided no thermoregulatory advantage; 2) maintenance of euhydration by oral fluid replacement ( approximately 85% of sweat fluid loss) during exercise in the heat was reflected in higher Q, SV, and SR with decreased heat storage; and 3) W or an isotonic CE solution was equally effective in reducing physiological strain associated with exercise-induced dehydration and heat stress.
Publication Date: 1998-06-11 PubMed ID: 9609799DOI: 10.1152/jappl.1998.84.6.2042Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The study investigates how varying hydration methods can impact horses’ physiological response during strenuous exercise in hot conditions. It found that maintaining hydration significantly reduced negative effects of exercise-induced dehydration and heat stress.
Research Aim and Methodology
The aim of the study was to explore how differing hydration methods – hyperhydration, exercise-induced dehydration and oral fluid replacement – could affect the physiological reactions of horses during periods of intensive exercise in a hot environment.
To perform the study, six horses were put through a 90-minute exercise regimen and repeated this process three times under different hydration conditions. The regimen consisted of two 45-minute exercise periods, with a 15-minute recovery phase in between. In a randomized order, the horses either received no fluid, 10 liters of water or a carbohydrate-electrolyte solution both two hours before the exercise protocol as well as in-between the two exercise periods.
Findings related to Hyperhydration
The study revealed that:
- Hyper-hydrating the horses before exercise, either with water or a carbohydrate-electrolyte solution, did not produce any significant changes in heart rate, cardiac output, stroke volume, core body temperature, sweating rate or sweating sensitivity during the initial exercise period.
Findings related to Dehydration
Related to exercise-induced dehydration:
- By the end of the second exercise period, horses that did not receive fluids showed a greater decrease in body weight indicating exercise-induced dehydration, leading to greater heat storage and core body temperature approximately 1.0 degrees Celsius higher than the other two groups (who had received water or carbohydrate-electrolyte solution).
- Further, these dehydrated horses showed significant decreases in cardiac output, stroke volume, sweating rate, and sensitivity to sweat.
The Effectiveness of Oral Fluid Replacement
As for the effects of oral fluid replacement:
- The researchers found that maintaining hydration (approximately 85% of sweat fluid loss) during exercise in hot conditions resulted in increased cardiac output, stroke volume, and sweating rate while reducing heat storage.
- Both water and the carbohydrate-electrolyte solution were equally effective at reducing physiological stress associated with exercise-induced dehydration and heat stress.
In conclusion, whilst pre-exercise hyperhydration offered no regulatory advantage, maintaining hydration during exercise proved beneficial in reducing physiological strain in horses. Both water and carbohydrate-electrolyte solutions proved equally effective in these circumstances.
Cite This Article
APA
Geor RJ, McCutcheon LJ.
(1998).
Hydration effects on physiological strain of horses during exercise-heat stress.
J Appl Physiol (1985), 84(6), 2042-2051.
https://doi.org/10.1152/jappl.1998.84.6.2042 Publication
Researcher Affiliations
- Department of Clinical Studies, Ontario Veterinary College, University of Guelph, Guelph, Ontario, Canada N1G 2W1. geor.1@osu.edu
MeSH Terms
- Animals
- Body Temperature / drug effects
- Body Temperature / physiology
- Body Water / physiology
- Body Weight / drug effects
- Body Weight / physiology
- Dehydration / physiopathology
- Dietary Carbohydrates / pharmacology
- Female
- Heat Stress Disorders / physiopathology
- Hematocrit
- Hemodynamics / drug effects
- Hemodynamics / physiology
- Horses / physiology
- Isotonic Solutions / pharmacology
- Male
- Physical Exertion / physiology
- Plasma Volume / drug effects
- Plasma Volume / physiology
- Sweating / physiology
Citations
This article has been cited 5 times.- Trigg LE, Lyons S, Mullan S. Risk factors for, and prediction of, exertional heat illness in Thoroughbred racehorses at British racecourses.. Sci Rep 2023 Mar 14;13(1):3063.
- Verdegaal EJMM, Howarth GS, McWhorter TJ, Delesalle CJG. Is Continuous Monitoring of Skin Surface Temperature a Reliable Proxy to Assess the Thermoregulatory Response in Endurance Horses During Field Exercise?. Front Vet Sci 2022;9:894146.
- Verdegaal EJMM, Howarth GS, McWhorter TJ, Boshuizen B, Franklin SH, Vidal Moreno de Vega C, Jonas SE, Folwell LE, Delesalle CJG. Continuous Monitoring of the Thermoregulatory Response in Endurance Horses and Trotter Horses During Field Exercise: Baselining for Future Hot Weather Studies.. Front Physiol 2021;12:708737.
- Sp N, Kang DY, Kim DH, Lee HG, Park YM, Kim IH, Lee HK, Cho BW, Jang KJ, Yang YM. Methylsulfonylmethane inhibits cortisol-induced stress through p53-mediated SDHA/HPRT1 expression in racehorse skeletal muscle cells: A primary step against exercise stress.. Exp Ther Med 2020 Jan;19(1):214-222.
- Walker WT, Callan RJ, Hill AE, Tisher KB. Effects of oral powder electrolyte administration on packed cell volume, plasma chemistry parameters, and incidence of colic in horses participating in a 6-day 162-km trail ride.. Can Vet J 2014 Aug;55(8):765-71.
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