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Journal of applied physiology (Bethesda, Md. : 1985)1993; 75(4); 1758-1766; doi: 10.1152/jappl.1993.75.4.1758

Muscle fiber type composition and fiber size in successfully and unsuccessfully endurance-raced horses.

Abstract: Triplicate biopsies from three different depths of the gluteus medius muscle were obtained in 36 endurance-raced horses, aged 8.42 +/- 2.85 yr. Twenty of the horses were considered excellent endurance performers according to the mean speed of their three fastest records in endurance events for the past 2 or 3 years, whereas 16 were moderate performers, with a mean racing speed < 12.5 km/h (in 120- to 180-km endurance rides), < 14 km/h (in 80- to 120-km endurance rides), or < 13.5 km/h (in 40- to 60-km endurance rides). Significant differences in muscle fiber type composition and fiber size were recorded; excellent performers had a higher percentage and a larger size of type I and type IIa fibers (high and low myosin adenosinetriphosphatase activity at pH 4.5, respectively) and a lower percentage of type IIb fibers (moderate myosin adenosinetriphosphatase activity at pH 4.5), including both type IIb oxidative (moderate to high NADH-tetrazolium reductase activity) and IIb nonoxidative (low NADH-tetrazolium reductase activity). The differences in distribution of myofiber types and in fiber sizes were more marked in the deeper parts compared with the superficial regions of muscle. Our results also imply a greater homogeneity among the fiber type sizes across the muscle in horses with a superior endurance performance than in horses that had been poorly or moderately endurance raced. Thus the results show that fiber type proportions and fiber size in equine skeletal muscle are directly related to the athletic ability of the horse for endurance events.
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Publication Date: 1993-10-01 PubMed ID: 8282629DOI: 10.1152/jappl.1993.75.4.1758Google Scholar: Lookup
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  • Journal Article
  • Research Support
  • Non-U.S. Gov't

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 study explores the correlation between muscle fiber type composition and size, and the endurance performance of racehorses. The analysis shows that horses with better endurance have higher percentages and larger sizes of certain muscle fiber types, thus implying that the type and size of muscle fibers play a crucial role in determining a horse’s athletic capabilities in endurance races.

Overview of the Study

  • The researchers conducted muscle biopsies on 36 endurance racehorses, with subset categories identified as excellent performers (20 horses) and moderate performers (16 horses) based on their average racing speeds.
  • The categorization of performance relied on the horse’s previous 2 or 3 years of racing records and set speed parameters for different race distances.
  • The purpose of this investigation was to find any noticeable differences in muscle fiber composition and size between these two groups of horses.

Findings of the Study

  • The study found that the excellent performers had a higher percentage and larger size of Type I and Type IIa muscle fibers. These fibers have high and low myosin Adenosine Triphosphate (ATPase) activity respectively under a pH of 4.5.
  • On the other hand, the excellent performing horses had a lesser proportion of Type IIb fibers, which have only moderate myosin ATPase activity under similar acidity conditions.
  • Among the Type IIb fibers, oxidative fibers (high reductase activity) and nonoxidative fibers (low reductase activity) were both found to be lower in proportion in high-performing horses.

Implications of the Study

  • The variations found in myofiber types and sizes were more prominently observed in the deep muscle tissues than in the superficial ones.
  • The study’s results suggest that horses with a more homogeneous distribution of fiber types and sizes throughout the muscle showed better endurance race performance.
  • Fonts with size variations across the muscle fiber types were typically observed in horses showing moderate to low performance in endurance races.
  • The findings of this research therefore imply that the distribution and size of muscle fibers in equine skeletal muscle are directly related to a horse’s athletic ability, particularly in endurance events.

Cite This Article

APA
Rivero JL, Serrano AL, Henckel P, Agüera E. (1993). Muscle fiber type composition and fiber size in successfully and unsuccessfully endurance-raced horses. J Appl Physiol (1985), 75(4), 1758-1766. https://doi.org/10.1152/jappl.1993.75.4.1758

Publication

Journal of applied physiology (Bethesda, Md. : 1985)
ISSN: 8750-7587
NlmUniqueID: 8502536
Country: United States
Language: English
Volume: 75
Issue: 4
Pages: 1758-1766

Researcher Affiliations

Rivero, J L
  • Department of Comparative Anatomy and Pathological Anatomy, Faculty of Veterinary Science, University of Cordoba, Spain.
Serrano, A L
    Henckel, P
      Agüera, E

        MeSH Terms

        • Aging / physiology
        • Animals
        • Body Composition
        • Female
        • Histocytochemistry
        • Horses
        • Male
        • Muscles / cytology
        • Muscles / enzymology
        • Muscles / metabolism
        • Myosins / metabolism
        • Orchiectomy
        • Physical Conditioning, Animal
        • Physical Endurance / physiology
        • Sex Characteristics

        Citations

        This article has been cited 19 times.
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