Muscle fibre type composition in untrained and endurance-trained Andalusian and Arab horses |
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Authors: | J L Lopez-Rivero J L Morales-Lopez A M Galisteo E Aguera |
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Institution: | Department of Comparative Anatomy and Pathological Anatomy, Faculty of Veterinary Sciences, University of Cordoba, Spain. |
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Abstract: | Muscle biopsies were taken from the middle gluteal muscle of 68 stallions (52 Andalusian AN] and 16 Arab AR]) ranging from six to 12 years of age. Seventeen AN horses and eight AR horses were untrained, while the remainder underwent active endurance training for 6 months. Fifteen AN horses were moderately endurance-trained while the other 20 AN horses and eight AR horses were strongly endurance-trained. Percentages of type I and type II fibres were similar in all groups (P greater than 0.05). The group of horses with the hardest training had a higher percentage of type IIA fibres (AN P less than 0.01; AR P less than 0.02) and a lower percentage of type IIB fibres (P less than 0.05 for AN and AR) than the untrained horses. All trained horses had a higher percentage of type IIB oxidative fibres and a lower percentage of type IIB non-oxidative fibres than the untrained horses (P less than 0.01 for both). These results suggest that the proportions of type I and type II fibres are highly stable within a given breed, but the stimulus of training facilitates changes both in contractile properties and, particularly, in the oxidative capacity of type II subgroups. |
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