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Equine veterinary journal2021; 54(5); 895-904; doi: 10.1111/evj.13519

Pre-race and race management impacts serum muscle enzyme activity in Australian endurance horses.

Abstract: Marked increases in serum muscle enzyme activity can occur in endurance horses but the diagnostic certainty in predicting cases of myopathy is unclear. Improved understanding of horse management effects on serum muscle enzyme activity as markers of muscle health would assist interpretation of serum muscle enzyme activity and guide management to reduce myopathy risk. Objective: To investigate associations between serum muscle enzyme activity and management factors in endurance horses. Methods: Cross-sectional study. Methods: One hundred endurance horses competing in four endurance events (offering distances of 20-120 km) in south-eastern Australia were observed. Data were collected from official horse logbooks, pre-and post-race serum samples, an owner questionnaire of pre-race and race management of horses and the Australian Endurance Riders Association results database. Multivariable linear regression modelling tested associations between management factors and serum muscle enzyme activity. Results: First leg speed, distance raced, number of rest days pre-race, and pre-race activity of aspartate aminotransferase (AST) and creatine kinase (CK) explained 47.3% of the variance in post-race CK. As first leg speed increased by 1 km/h, CK activity increased by 25.8% (95% CI 11%-35%). Race distances >80 km increased post-race CK activity by 124% (95% CI 116%-145%). Each additional pre-race rest day increased post-race CK activity by 30.5% (95% CI 11%-42%). Modelling a 10% increase in pre-race CK and pre-race AST activity was associated with post-race CK activity increasing by 7.3% (95% CI 3%-14.4%) and 8.5% (95% CI 0.3%-14.2%) respectively. Horses experiencing training distances >40 km and a greater number of rest days prior to race day developed increased pre-race AST and CK activity respectively. Conclusions: Owner questionnaires may be subject to bias. Limited data were available to model ride terrain, horse fitness, ration detail and myopathy. Muscle biopsies were not used to confirm myopathy. Conclusions: Nearly half of the variation in post-race CK activity observed can be attributed to management factors unrelated to myopathy, suggesting increased CK activity may not be pathognomonic for myopathy. We advise caution in relying solely on serum muscle enzyme activity for diagnosis of myopathy until the strength of association between CK and myopathy is further ascertained in future studies.
© 2021 The Authors. Equine Veterinary Journal published by John Wiley & Sons Ltd on behalf of EVJ Ltd.
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Publication Date: 2021-11-08 PubMed ID: 34601756PubMed Central: PMC9545901DOI: 10.1111/evj.13519Google Scholar: Lookup
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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.

The study explores how pre-race and race management influence the levels of muscle enzyme activity in endurance horses, aiming to enhance understanding of equine muscle health and minimize the chances of developing myopathy.

Research Methodology

  • Horses under investigation were those participating in four endurance events ranging from 20 to 120 kilometers in Southeast Australia.
  • The researchers collected data from several sources such as official horse logbooks, pre-and post-race serum samples, owner questionnaires regarding horse management before and during the race, and the Australian Endurance Riders Association results database.
  • The possible associations between management factors and muscle enzyme activity in the horse’s serum were examined through multivariable linear regression modelling.

Findings

  • Main factors impacting post-race creatine kinase (CK), a muscle enzyme, activity were first leg speed, race’s distance, number of pre-race rest days, and initial levels of aspartate aminotransferase (AST) and CK.
  • These factors accounted for 47.3% variance in post-race CK levels.
  • The researchers found that an increase in first leg speed by 1 km/h resulted in a 25.8% increase in CK activity, and races exceeding 80 km increased post-race CK activity by 124%.
  • Horses that experienced longer training distances (>40 km) and a larger number of rest days before the race date had raised pre-race AST and CK activity.

Conclusion

  • The study ends by acknowledging the possible bias in owner questionnaires and the lack of detailed data modeling ride terrain, horse fitness, ration detail, and myopathy.
  • It also highlights the absence of muscle biopsies to confirm myopathy.
  • It points out that almost half of the post-race CK activity variance is tied to management elements that are unrelated to myopathy, indicating that increased CK activity may not always signify myopathy.
  • The study advises against solely relying on serum muscle enzyme activity for detecting myopathy and suggests future research to further determine the link between CK and myopathy.

Cite This Article

APA
Buckley P, Buckley DJ, Freire R, Hughes KJ. (2021). Pre-race and race management impacts serum muscle enzyme activity in Australian endurance horses. Equine Vet J, 54(5), 895-904. https://doi.org/10.1111/evj.13519

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English
Volume: 54
Issue: 5
Pages: 895-904

Researcher Affiliations

Buckley, Petra
  • School of Animal and Veterinary Sciences, Charles Sturt University, Wagga Wagga, New South Wales, Australia.
Buckley, David J
  • Clinical Governance Unit, Murrumbidgee Local Health District, Wagga Wagga, New South Wales, Australia.
Freire, Rafael
  • School of Animal and Veterinary Sciences, Charles Sturt University, Wagga Wagga, New South Wales, Australia.
Hughes, Kristopher J
  • School of Animal and Veterinary Sciences, Charles Sturt University, Wagga Wagga, New South Wales, Australia.

MeSH Terms

  • Animals
  • Australia
  • Creatine Kinase
  • Cross-Sectional Studies
  • Horse Diseases
  • Horses
  • Muscles
  • Muscular Diseases / veterinary
  • Physical Conditioning, Animal / physiology
  • Physical Endurance / physiology

Grant Funding

  • Charles Sturt University
  • Willinga Park, Bawley Point 2539, Australia

Conflict of Interest Statement

No competing interests have been declared.

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Citations

This article has been cited 5 times.
  1. Mecocci S, Porzio E, Chiaradia E, Pepe M, Paris A, Bergagna S, Pietrucci D, Chillemi G, Beccati F, Cappelli K. Omic technology to monitoring resilience and adaptation to exercise and heat stress in endurance horses. Front Vet Sci 2025;12:1734969.
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  2. James C, Sheahan J, Arthur P. Stable Levels of Thiol-Oxidised Plasma Albumin, a Biomarker of Oxidative Stress, Is Correlated with Enhanced Performance in Australian Thoroughbred Racehorses. Animals (Basel) 2025 Dec 12;15(24).
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  3. Rump-Dierig I, Giers J, Frenzel C, Stöckle S, Gehlen H. Seasonal Trends in Cardiac Troponin I Concentration and Creatine Kinase and Aspartate Aminotransferase Enzyme Activity in Relation to Myocardial Velocity Rates in Eventing Horses. Animals (Basel) 2025 Nov 3;15(21).
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  4. James C, Lloyd EM, Arthur PG. The Level of Thiol-Oxidised Plasma Albumin Is Elevated Following a Race in Australian Thoroughbred Horses. Vet Med Sci 2025 Jul;11(4):e70487.
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