Affiliations: [a] 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 | [b] Department of Physiotherapy, Federal University of São Carlos, São Carlos, São Paulo, Brazil | [c] Faculty of Medicine of Ribeirão Preto, Psychiatry and Medical Psychology, Department of Neurology, University of São Paulo, Ribeirão Preto, São Paulo, Brazil | [d] Faculty of Medicine of Ribeirão Preto, Department of Social Medicine, University of São Paulo, Ribeirão Preto, São Paulo, Brazil
Correspondence:
[*]
Address for correspondence: Ana Claudia Mattiello Sverzut, Faculty of Medicine of Ribeirão Preto, Medicine and Rehabilitation of the Locomotor Apparatus, Department of Biomechanics, University of São Paulo, Av. Bandeirantes, 3900. 14049-800 Ribeirão Preto, SP, Brazil. E-mail: acms@fmrp.usp.br
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.
