Left ventricular size and systolic function in Thoroughbred racehorses and their relationships to race performance.
Abstract: Cardiac morphology in human athletes is known to differ, depending on the sports-specific endurance component of their events, whereas anecdotes abound about superlative athletes with large hearts. As the heart determines stroke volume and maximum O(2) uptake in mammals, we undertook a study to test the hypothesis that the morphology of the equine heart would differ between trained horses, depending on race type, and that left ventricular size would be greatest in elite performers. Echocardiography was performed in 482 race-fit Thoroughbreds engaged in either flat (1,000-2,500 m) or jump racing (3,200-6,400 m). Body weight and sex-adjusted measures of left ventricular size were largest in horses engaged in jump racing over fixed fences, compared with horses running shorter distances on the flat (range 8-16%). The observed differences in cardiac morphologies suggest that subtle differences in training and competition result in cardiac adaptations that are appropriate to the endurance component of the horses' event. Derived left ventricular mass was strongly associated with published rating (quality) in horses racing over longer distances in jump races (P < or = 0.001), but less so for horses in flat races. Rather, left ventricular ejection fraction and left ventricular mass combined were positively associated with race rating in older flat racehorses running over sprint (<1,408 m) and longer distances (>1,408 m), explaining 25-35% of overall variation in performance, as well as being closely associated with performance in longer races over jumps (23%). These data provide the first direct evidence that cardiac size influences athletic performance in a group of mammalian running athletes.
Publication Date: 2005-05-26 PubMed ID: 15920096DOI: 10.1152/japplphysiol.01319.2004Google Scholar: Lookup
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- Comparative Study
- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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This research seeks to establish the correlation between the size and functionality of the left ventricle in Thoroughbred horse hearts and their performance in racing. The studies indicate a clear relationship whereby horses with greater left ventricular size performed better in longer races, substantiating the first firm evidence of cardiac size influencing athletic performance in mammalian running athletes.
Study Purpose and Hypothesis
- The research was primarily aimed at analyzing the impacts of cardiac size, particularly the left ventricle, on the racing performance of Thoroughbred horses.
- In light of existing knowledge regarding varying heart morphology depending on sports-specific endurance in human athletes, the hypothesis of the study was that equine heart morphology would vary among trained horses based on the type of race, and that elite performers would exhibit the largest left ventricular sizes.
Methodology
- An extensive sample of 482 race-fit Thoroughbreds that participated in either flat (1,000-2,500 m) or jump racing (3,200-6,400 m) was used in the study.
- Echocardiography was utilized in examining the horses’ hearts, concentrating on the left ventricle’s size and function.
- These measurements were adjusted according to body weight and sex to ensure a fair comparison.
Findings
- Horses involved in jump racing over fixed fences presented larger body weight and sex-adjusted measures of left ventricular size than those running shorter distances on the flat. The variation in size ranged between 8 and 16%.
- This suggests that distinct differences in training and competition lead to suitable cardiac adaptations in relation to the endurance element of the horses’ event.
- The research also revealed a robust association between derived left ventricular mass and quality rating in horses participating in longer jump races, with the statistical significance marked at P < or = 0.001.
- The correlation was less prominent for horses in flat races. On the contrary, left ventricular ejection fraction and left ventricular mass combined were positively associated with race rating in older flat racehorses running across different distances.
- These combined aspects explained between 25-35% of overall variation in performance and were also closely linked to performance in longer jump races, accounting for 23% of the variance.
Conclusion
- This study presents direct evidence that cardiac size, or more precisely, the size of the left ventricle, influences athletic performance amongst mammalian running athletes; in this case, Thoroughbred racehorses.
- The findings confirm that the heart, determining stroke volume and maximum O(2) uptake in mammals, plays a tangible role in influencing the racing capabilities of these horses.
- This has implications for understanding the physical factors contributing to equine performance, with potential impacts on training and breeding practices.
Cite This Article
APA
Young LE, Rogers K, Wood JL.
(2005).
Left ventricular size and systolic function in Thoroughbred racehorses and their relationships to race performance.
J Appl Physiol (1985), 99(4), 1278-1285.
https://doi.org/10.1152/japplphysiol.01319.2004 Publication
Researcher Affiliations
- Centre for Equine Studies, Animal Health Trust, Newmarket, Suffolk, UK. lesley.young@aht.org.uk
MeSH Terms
- Adaptation, Physiological
- Aging / physiology
- Animal Husbandry
- Animals
- Echocardiography
- Female
- Heart / physiology
- Heart Ventricles
- Horses / physiology
- Male
- Physical Conditioning, Animal
- Running / physiology
- Stroke Volume
- Systole
- Task Performance and Analysis
Citations
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- Wang T, Meng J, Peng X, Huang J, Huang Y, Yuan X, Li X, Yang X, Chang X, Zeng Y, Yao X. Metabolomics analysis and mRNA/miRNA profiling reveal potential cardiac regulatory mechanisms in Yili racehorses under different training regimens. PLoS One 2025;20(7):e0322468.
- Bayly WM, Leguillette R, Sides RH, Massie S, Guigand C, Jones KB, Warlick LM, Thueson EL, Troudt TA, Slocombe RF, Jones JH. Equine exercise-induced pulmonary hemorrhage: the role of high left-heart pressures secondary to exercise-induced hypervolemia, and high inspiratory pressures. J Appl Physiol (1985) 2024 Nov 1;137(5):1359-1373.
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