title: Skeletal muscle characteristics in young trained and untrained standardbred trotters.
abstract: Muscle biopsies were taken from the middle gluteal muscle of 28 Standardbred trotters, 3-4 years of age. The 13 horses in Group T were trained consistently from 18 months of age, whereas the 15 horses in Group UT were not exposed to any systematic training before 3 years of age. Group T horses had a lower percentage of Type IIB fibres (31%) than did Group UT horses (39%). Citrate synthase (CS) activity, representing oxidative capacity, was higher in Group T (72 mmol kg-1 min-1) than in Group UT (47 mmol kg-1 min-1). Biopsies were taken from 4 horses in each group when they were foals and then annually until 3-4 years of age. Results from this study indicate that regular training of Standardbreds from 18 months of age resulted in increased CS activity and a decrease in the percentage of Type IIB fibres. This study shows that training, not growth, is the main factor that induces a high oxidative capacity and a high Type IIA/IIB fibre ratio in muscle of Standardbred trotters.
authors.affiliation: Department of Medicine and Surgery, Faculty of Veterinary Medicine, Swedish University of Agricultural Sciences, Uppsala.
authors.forename: M
authors.initials: M
authors.lastname: Ronéus
authors.forename: B
authors.initials: B
authors.lastname: Essén-Gustavsson
authors.forename: A
authors.initials: A
authors.lastname: Lindholm
authors.forename: S G
authors.initials: SG
authors.lastname: Persson
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001707:Biopsy, Needle / Q000662:veterinary; D002081:Buttocks; D002950:Citrate (si)-Synthase / Q000032:analysis; D005260:Female; D006651:Histocytochemistry; D006736:Horses / Q000033:anatomy & histology* / Q000502:physiology; D008297:Male; D024510:Muscle Development; D009132:Muscles / Q000033:anatomy & histology* / Q000201:enzymology; D010084:Oxidation-Reduction; D010805:Physical Conditioning, Animal; D012044:Regression Analysis
chemical_list: D002950:Citrate (si)-Synthase