Sweating rate and sweat composition during exercise and recovery in ambient heat and humidity.
Abstract: The objective of this study was to determine the composition and extent of sweat losses during submaximal exercise under hot and humid conditions and to compare these findings with the same exercise protocol conducted under cool, dry and hot, dry conditions. Five Thoroughbred horses (age 3 to 6) completed exercise tests under each of 3 environmental conditions in random order: cool, dry (CD), room temperature (T) = 20 degrees C, relative humidity (RH) = 45-55%; hot, dry (HD), T = 32-34 degrees C, RH = 45-55%; and hot, humid (HH), T = 32-34 degrees C, RH = 80-85%. Horses exercised at 50% of their predetermined VO2max on a treadmill set at a 10% slope until attainment of a pulmonary artery blood temperature of 41.5 degrees C followed by a 60 min recovery. Sweat was collected from a sealed polyethylene pouch enclosing a 150 cm2 area on the lateral thorax. During exercise and the first 30 min of recovery, sweat fluid losses were 7.9 +/- 0.7 litres, 9.9 +/- 0.5 litres and 6.6 +/- 1.2 litres (mean +/- s.e.m.) for CD, HD and HH, respectively. Sweating rate (SR), calculated from sweat volume per unit area of enclosed skin, was lowest in CD and similar in HD and HH during exercise such that at end of exercise in HH (16.5 min) calculated sweat losses were approximately 5% and 32% higher than in HD and CD, respectively. In recovery, SR declined in all conditions but was significantly lower in CD (P < 0.05). Sweating was detectable until 30 min recovery in CD, 45 min recovery in HD and 60 min recovery in HH. Sweat composition and osmolality was different under the 3 environmental conditions and changed gradually during exercise and recovery in all conditions. Osmolality and [Na] was highest in HD and lowest in CD. During exercise, [Na] increased with increasing SR. Although exercise duration was significantly decreased in HH (16.5 +/- 1 min) when compared to HD (28 +/- 2 min) and CD (37 +/- 2 min), fluid and ion losses in HH were comparable to those in HD as a result of a high SR and prolonged sweating during recovery.
Publication Date: 1995-11-01 PubMed ID: 8933099DOI: 10.1111/j.2042-3306.1995.tb05022.xGoogle Scholar: Lookup
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Summary
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This study examines the impact of different environmental conditions on sweat rates and sweat composition in Thoroughbred horses during physical activity and recovery. It specifically compares outcomes under hot and humid conditions to those under hot, dry and cool, dry conditions.
Research Design and Methodology
- Five Thoroughbred horses aged between 3 to 6 years were made to undergo exercise tests under each of three different environmental conditions in random order. These conditions were: “cool, dry” (CD), “hot, dry” (HD), and “hot, humid” (HH).
- The horses performed the exercise tests at half of their maximum oxygen consumption capabilities (50% VO2max) on a treadmill set at a 10% slope.
- The tests continued until a pulmonary artery blood temperature of 41.5 degrees Celsius was reached, followed by a period of recovery lasting 60 minutes.
- Sweat was gathered from an area of the horse’s thorax enclosed by a sealed polyethylene pouch.
Results of the Study
- Throughout the exercise and the first recovery half hour, sweat fluid losses were different for each condition, being highest in HD and lowest in HH.
- The calculated sweat volume per skin unit, or sweat rate (SR), was lowest in CD and similar in both HD and HH during exercise.
- In HH, calculated sweat losses by the end of exercise were about 5% and 32% higher than HD and CD respectively.
- During the recovery phase, all conditions saw a decline in SR, but it was significantly lower in CD.
- Sweating was observable for a duration of 30 minutes of recovery in CD, 45 minutes in HD, and 60 minutes in HH.
Analysis of Sweat Composition
- Changes in sweat composition and osmolality were found in the different environmental conditions and also changed gradually over the course of the exercise and recovery in all situations.
- The highest osmolality and sodium concentration was found in HD while the lowest was in CD.
- During exercise, sodium concentration increase coincided with an increase in the sweat rate.
- Despite shorter exercise duration in HH conditions when compared to HD and CD, fluid and ion losses in HH were comparable to those in HD due to a higher sweat rate and longer recovery sweating.
Cite This Article
APA
McCutcheon LJ, Geor RJ, Hare MJ, Ecker GL, Lindinger MI.
(1995).
Sweating rate and sweat composition during exercise and recovery in ambient heat and humidity.
Equine Vet J Suppl(20), 153-157.
https://doi.org/10.1111/j.2042-3306.1995.tb05022.x Publication
Researcher Affiliations
- Ontario Veterinary College, Guelph, Canada.
MeSH Terms
- Animals
- Body Temperature
- Electrolytes / analysis
- Exercise Test / veterinary
- Horses / physiology
- Hot Temperature
- Humidity
- Osmolar Concentration
- Physical Conditioning, Animal / physiology
- Proteins / analysis
- Sweat / chemistry
- Sweating
- Time Factors
Citations
This article has been cited 9 times.- Harvey AM, Ramp D, Mellor DJ. Review of the Foundational Knowledge Required for Assessing Horse Welfare.. Animals (Basel) 2022 Dec 1;12(23).
- Lindinger MI. Oral Electrolyte and Water Supplementation in Horses.. Vet Sci 2022 Nov 10;9(11).
- Lindinger MI, Waller AP. Physicochemical Analysis of Mixed Venous and Arterial Blood Acid-Base State in Horses at Core Temperature during and after Moderate-Intensity Exercise.. Animals (Basel) 2022 Jul 22;12(15).
- 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.
- Klous L, Siegers E, van den Broek J, Folkerts M, Gerrett N, van Oldruitenborgh-Oosterbaan MS, Munsters C. Effects of Pre-Cooling on Thermophysiological Responses in Elite Eventing Horses.. Animals (Basel) 2020 Sep 16;10(9).
- Templeman JR, McCarthy N, Lindinger MI, Shoveller AK. Changes in salivary electrolyte concentrations in mid-distance trained sled dogs during 12 weeks of incremental conditioning.. Physiol Rep 2020 Jun;8(12):e14493.
- Muñoz CX, Wininger M. Models of hydration and nutrition require environmental data.. Public Health Nutr 2020 Apr;23(6):971-973.
- Zeyner A, Romanowski K, Vernunft A, Harris P, Müller AM, Wolf C, Kienzle E. Effects of Different Oral Doses of Sodium Chloride on the Basal Acid-Base and Mineral Status of Exercising Horses Fed Low Amounts of Hay.. PLoS One 2017;12(1):e0168325.
- Agar C, Gemmill R, Hollands T, Freeman SL. The use of nutritional supplements in dressage and eventing horses.. Vet Rec Open 2016;3(1):e000154.
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