title: Muscle fibre type composition in untrained and endurance-trained Andalusian and Arab horses.
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.
authors.affiliation: Department of Comparative Anatomy and Pathological Anatomy, Faculty of Veterinary Sciences, University of Cordoba, Spain.
authors.forename: J L
authors.initials: JL
authors.lastname: Lopez-Rivero
authors.forename: J L
authors.initials: JL
authors.lastname: Morales-Lopez
authors.forename: A M
authors.initials: AM
authors.lastname: Galisteo
authors.forename: E
authors.initials: E
authors.lastname: Aguera
mesh_terms: D000818:Animals; D001706:Biopsy / Q000662:veterinary; D001947:Breeding; D006651:Histocytochemistry; D006736:Horses / Q000033:anatomy & histology* / Q000502:physiology; D008297:Male; D009119:Muscle Contraction; D009132:Muscles / Q000033:anatomy & histology* / Q000502:physiology; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D010805:Physical Conditioning, Animal