title: Change in the contractile behavior of muscle fibers in subjects with primary muscle dysfunction.
abstract: The mechanical and metabolic characteristics of skeletal muscle fibers can interfere with muscle contractile performance in healthy subjects. Few studies have investigated the degree of association between muscle function and muscle fiber morphology in patients with myopathy. A biopsy was obtained from the left biceps brachii muscle of 12 subjects with myopathic disorders. The relative cross-sectional area of type 2 fibers and their subtypes was determined by the ATPase technique. Relative torque (RT) was calculated by dividing isokinetic elbow flexion peak torque (PT) values (90 and 180° s-1) by isometric PT values. Correlations were analyzed using Spearman's coefficient (r). The relative cross-sectional area of type 2b fibers was positively correlated with RT90 (r = 0.71, P = 0.009) and RT180 (r = 0.73, P = 0.007). The relative cross-sectional area of type 2a fibers showed a moderate and negative correlation with RT180 (r = -0.62, P = 0.03) and a low correlation with RT90 (r = -0.57, P = 0.05). In contrast to healthy subjects, patients with myopathy presented changes in the contractile behavior of type 2a fibers and compensatory adaptations in type 2b fibers. The results suggest that RT in combination with morphometric parameters provides data regarding muscle function in patients with myopathic disorders and can contribute to the establishment of therapeutic exercises.
authors: Faculty of Medicine of Ribeirão Preto, Medicine and Rehabilitation of the Locomotor Apparatus, Department of Biomechanics, University of São Paulo, Ribeirão Preto, São Paulo, Brazil.
authors: Claudio Gregório Nuernberg
authors: CG
authors: Back
authors: Priscila C O
authors: PC
authors: Benedini-Elias
authors: Stela M
authors: SM
authors: Mattiello
authors: Claudia
authors: C
authors: Sobreira
authors: Edson Z
authors: EZ
authors: Martinez
authors: Ana Claudia
authors: AC
authors: Mattiello-Sverzut
mesh_terms: D000251:Adenosine Triphosphatases / Q000378:metabolism; D003402:Creatine Kinase / Q000097:blood; D003430:Cross-Sectional Studies; D004551:Elbow Joint / Q000294:innervation / Q000503:physiopathology; D004576:Electromyography; D005260:Female; D006801:Humans; D008297:Male; D009068:Movement / Q000502:physiology; D009119:Muscle Contraction / Q000502:physiology*; D018485:Muscle Fibers, Skeletal / Q000201:enzymology / Q000502:physiology*; D053581:Muscle Strength Dynamometer; D009135:Muscular Diseases / Q000473:pathology*; D018709:Statistics, Nonparametric; D019415:Torque
chemical_list: D003402:Creatine Kinase; D000251:Adenosine Triphosphatases