Muscular design in the equine interosseus muscle.
Abstract: We studied the forelimb interosseus muscle in horses, Equus caballus, to determine the muscular properties inherent in its function. Some authors have speculated that the equine interosseus contains muscle fibers at birth only to undergo loss of these fibers through postnatal ontogeny. We describe the muscle fibers in eight interosseus specimens from adult horses. These fibers were studied histochemically using myosin ATPase studies and immunocytochemically using several antibodies directed against type I and type II myosin heavy chain antibodies. We determined that 95% of the fibers were type I, presumed slow-twitch fibers. All fibers exhibited normal morphological appearance in terms of fiber diameter and cross-sectional area, suggesting that the muscles are undergoing normal cycles of recruitment. SDS-PAGE studies of myosin heavy chain isoforms were consistent with these observations of primarily slow-twitch muscle. Fibers were determined to be approximately 800 microm long when studied using nitric acid digestion protocols. Short fiber length combined with high pinnation angles suggest that the interosseus muscle is able to generate large amounts of force but can produce little work (measured as pulling the distal tendon proximally). While the equine interosseus muscle has undergone a general reduction of muscle content during its evolution, it remains composed of a significant muscular component that likely contributes to forelimb stability and elastic storage of energy during locomotion.
J. Morphol. (c) 2006 Wiley-Liss, Inc.
Publication Date: 2006-03-03 PubMed ID: 16511864DOI: 10.1002/jmor.10433Google Scholar: Lookup
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- Journal Article
- Research Support
- Non-U.S. Gov't
- Research Support
- U.S. Gov't
- Non-P.H.S.
Summary
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The research article investigates the properties and functionality of the interosseus muscle in a horse’s forelimb, revealing how the muscle contributes to the animal’s mobility and has evolved to optimize force production over extended work capacity.
About the Study
- The research was conducted on the forelimb interosseus muscle of the horse species, Equus caballus, to discover inborn muscular qualities related to its function. This chosen muscle has been suggested to contain muscle fibers at birth, which are believed to decrease through postnatal ontogeny – the process of an individual’s evolution or development from an early stage to maturity.
Methodology
- The researchers examined muscle fibers in eight interosseus samples from adult horses to validate the postnatal ontogeny theory.
- They employed histochemical examination using myosin ATPase studies and immunocytochemical examination using several antibodies that target type I and type II myosin heavy chain antibodies, with the latter being a crucial protein component of muscle fibers.
Findings
- A significant 95% of the muscle fibers were identified as type I, presumed to be slow-twitch fibers. These fibers are known for their endurance and efficiency in energy usage over long periods, suggesting that they are optimised for a horse’s sustained locomotion.
- All fibers had a normal morphological appearance, as determined by fiber diameter and cross-sectional area. This is an indication that the muscles are undergoing normal cycles of recruitment – the process of replacing damaged muscle fibers with new ones.
- On further examination, the research found that the muscle fibers were approximately 800 microm long when observed using nitric acid digestion protocols.
Implications and Conclusions
- The short length of the muscle fibers, coupled with high pinnation angles, implied that the interosseus muscle can produce high levels of force but is limited in doing extensive work, as measured by the task of pulling the distal tendon proximally.
- Despite the general decline of muscle content in the equine interosseus muscle during evolution, it remains a significant muscular component that contributes to a horse’s forelimb stability and energy storage system during locomotion.
Cite This Article
APA
Soffler C, Hermanson JW.
(2006).
Muscular design in the equine interosseus muscle.
J Morphol, 267(6), 696-704.
https://doi.org/10.1002/jmor.10433 Publication
Researcher Affiliations
- College of Veterinary Medicine, Cornell University, Ithaca, New York 14853-6401, USA. jwh6@cornell.edu
MeSH Terms
- Animals
- Female
- Forelimb / anatomy & histology
- Horses
- Male
- Muscle Contraction
- Muscle Fibers, Slow-Twitch / ultrastructure
- Muscle, Skeletal / anatomy & histology
- Muscle, Skeletal / metabolism
- Myosin Heavy Chains / metabolism
- Myosins / metabolism
Citations
This article has been cited 5 times.- Mossor AM, Austin BL, Avey-Arroyo JA, Butcher MT. A Horse of a Different Color?: Tensile Strength and Elasticity of Sloth Flexor Tendons. Integr Org Biol 2020;2(1):obaa032.
- MacLaren JA. Biogeography a key influence on distal forelimb variation in horses through the Cenozoic. Proc Biol Sci 2021 Jan 13;288(1942):20202465.
- May-Davis S, Vermeulen Z, Brown WY. A Primitive Trait in Two Breeds of Equus Caballus Revealed by Comparative Anatomy of the Distal Limb. Animals (Basel) 2019 Jun 14;9(6).
- Butcher MT, Chase PB, Hermanson JW, Clark AN, Brunet NM, Bertram JE. Contractile properties of muscle fibers from the deep and superficial digital flexors of horses. Am J Physiol Regul Integr Comp Physiol 2010 Oct;299(4):R996-R1005.
- Guest DJ, Birch HL, Thorpe CT. A review of the equine suspensory ligament: Injury prone yet understudied. Equine Vet J 2025 Sep;57(5):1167-1182.
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