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Muscle Fibre Type Distribution of the Thoracolumbar and Hindlimb Regions of Horses: Relating Fibre Type and Functional Role
Author(s) -
Hyytiäinen H,
Mykkänen A,
HielmBjörkman A,
Stubbs N,
McGowan C
Publication year - 2014
Publication title -
equine veterinary journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.82
H-Index - 87
eISSN - 2042-3306
pISSN - 0425-1644
DOI - 10.1111/evj.12267_162
Subject(s) - longissimus dorsi , anatomy , hindlimb , myosin , horse , medicine , chemistry , biology , zoology , biochemistry , paleontology
The muscle fibre type ( MFT ) of the deep epaxial musculature has not been determined in horses. The objective was to determine the MFT distribution in selected muscles of thoracolumbar and hindlimb region of horses. This included deep epaxial and hypaxial muscles that were hypothesised to have a postural stabilising role. A second objective was to examine differences in MFT distribution between Arabians and Q uarter horses. Methods Muscle biopsy samples (114) were obtained from 5 Q uarter horses, 4 Arabians, and 2 T horoughbreds. The myosin heavy chain distribution was determined by gel electrophoresis. M ann‐ W hitney rank test was used to compare the proportional MFT content and differences between breeds. Results Mm. sacrocaudalis dorsalis medialis and diaphragm had the highest proportion of MFT ‐ I , 84.1% (±18.4) and 72.4% (±12.5), respectively. The remaining deep epaxial muscles and the hypaxial m. psoas minor had approximately equal MFT ‐ I and II proportions. Mm. psoas major, iliocostalis, longissimus dorsi and the hind limb muscles contained mostly MFT‐IIX : from 50.5% (±12.8) to 67.9% (±7.3). Q uarter horses had significantly more MFT‐IIX in m. psoas major 60.8% (±9.1) than Arabians 41.9% (±3.2). Arabians had significantly more MFT ‐ I fibres in m. longissimus dorsi 16.9% (±4.6) than Q uarter horses 9.9% (±1.4) (P<0.05). Conclusions The MFT distribution of the deep epaxial muscles, mm. psoas minor and diaphragm, suggest a postural stabilizing role in contrast to the fibre type proportions of the hindlimb muscles. The findings can direct diagnosis, prevention and treatment of muscular or neuromotor dysfunction in the thoracolumbar and hind limb area. Ethical Animal Research The study was approved by the U niversity of Q ueensland A nimal E thics C ommittee. Explicit owner informed consent for participation in this study is not stated. Sources of funding: none. Competing interests: none.