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Thermoregulatory-induced compromise of muscle blood flow in ponies during intense exercise in the heat: a contributor to the onset of fatigue?
Abstract: Cardiac output (Q) and tissue blood flows (BF) were measured in four ponies at rest, after 30 min of moderate exercise (ME) (approximately 30% VO2max) and following moderately intense exercise (M-IE) (approximately 65%) until fatigue, in a mildly hot (MH) environment (dry bulb temperature = 41 degrees C, wet bulb temperature = 27.5 degrees C). Exercise at both intensities resulted in increases in Q (15.6 +/- 1.7 [rest] vs. 35.8 +/- 2.6 [ME] vs. 48.6 +/- 3.9 [M-IE] l/min) and VO2 (4.7 +/- 0.9 vs. 24.5 +/- 1.2 vs. 55.8 +/- 5.8 ml/kg/min). When compared to ME, M-IE resulted in decreases in BF to the skin (approximately 15%), nonworking muscle (46%), fat (93%), gut (56%), kidneys (57%), CNS (31-66%) and an increase in BF to respiratory (68%), limb (98.5%) and cardiac (50%) muscles. In contrast, BF to working muscle during ME in thermoneutral (TN) conditions (McConaghy et al. 2002) was higher than found during ME in MH. We calculated that limb BF was approximately 25% lower for ME in MH vs. ME in TN. Similarly, we estimated that limb BF during M-IE in MH was approximately 25% lower than for M-IE in TN. Attenuation of the increases in muscle BF during exercise in the heat may be a determinant of the onset of fatigue.
Publication Date: 2002-10-31 PubMed ID: 12405739DOI: 10.1111/j.2042-3306.2002.tb05471.xGoogle Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
Summary
This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.
This research investigates how heat affects the distribution of blood flow in ponies during intense exercise and how this might contribute to the occurrence of fatigue. It finds a change in how blood is distributed throughout the body during intense exercise in hot conditions, compared to those under thermoneutral conditions, which potentially impacts the onset of fatigue.
Research Process
The study involved monitoring the cardiac output and tissue blood flows in four ponies during three different conditions:
- Rest
- 30 minutes of moderate exercise (ME) equal to 30% of VO2max
- Moderately intense exercise (M-IE) equal to 65% of VO2max until fatigue
The tests were conducted in a mildly hot (MH) environment, featuring a dry bulb temperature of 41 degrees Celsius and a wet bulb temperature of 27.5 degrees Celsius.
Findings
Exercise at both intensities led to increases in the ponies’ cardiac output (Q) and oxygen consumption (VO2). However, comparisons between moderate and strenuous exercise showed that more intense activity resulted in decreased blood flow to several areas of the body.
- Decreases of blood flow included skin (~15%), non-working muscle (46%), fat (93%), gut (56%), kidneys (57%), and CNS (31-66%).
- Increases in blood flow were identified in the respiratory (68%), limb (98.5%), and the cardiac (50%) muscles.
The research highlighted that blood flow to working muscles was higher in thermoneutral conditions compared to hot ones. Calculations indicate that limb blood flow was approximately 25% lower during exercise in hot conditions compared to thermoneutral ones.
Implications
The research suggests that heat-induced changes in muscle blood flow during exercise might contribute to the onset of fatigue in ponies. This discovery may improve understanding of the limitations and risks of equine performance in different environmental conditions, helping to improve training and competition practices for equine athletes.
Cite This Article
APA
McConaghy FF, Hodgson DR, Hales JR, Rose RJ.
(2002).
Thermoregulatory-induced compromise of muscle blood flow in ponies during intense exercise in the heat: a contributor to the onset of fatigue?
Equine Vet J Suppl(34), 491-495.
https://doi.org/10.1111/j.2042-3306.2002.tb05471.x Publication
Researcher Affiliations
- University Veterinary Centre, Faculty of Veterinary Science, University of Sydney, Camden, New South Wales, Australia.
MeSH Terms
- Animals
- Body Temperature Regulation / physiology
- Cardiac Output / physiology
- Fatigue / etiology
- Fatigue / physiopathology
- Fatigue / veterinary
- Horses / physiology
- Hot Temperature
- Male
- Muscle, Skeletal / blood supply
- Oxygen Consumption / physiology
- Physical Conditioning, Animal / physiology
- Physical Exertion / physiology
- Regional Blood Flow / physiology
- Rest / physiology
Citations
This article has been cited 4 times.- Kang H, Zsoldos RR, Sole-Guitart A, Narayan E, Cawdell-Smith AJ, Gaughan JB. Heat stress in horses: a literature review. Int J Biometeorol 2023 Jun;67(6):957-973.
- 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.
- Kang H, Zsoldos RR, Skinner JE, Gaughan JB, Mellor VA, Sole-Guitart A. The Use of Percutaneous Thermal Sensing Microchips to Measure Body Temperature in Horses during and after Exercise Using Three Different Cool-Down Methods. Animals (Basel) 2022 May 14;12(10).
- 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.
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