Treadmill low-intensity training mediates fibrosis and maintains the function of dystrophic muscle: Understanding the effects over time

Abstract

Background. Dystrophic skeletal muscle undergoes fast degeneration and therapeutic exercise is controversial in this condition. The aim of this study was investigate the effects of a low-intensity training protocol on muscle fibrosis and function of the mdx model. Methods. Mdx male animals with 8 weeks of age were (T0; n=8) underwent a protocol of eight weeks at a horizontal treadmill (9 m/min, 3x/week, 30 min/day). Mdx animals were randomly allocated at the Trained group (mdx-T, n=8) or sedentary (mdx-NT, n=8). In vivo functional measurements of strength and performance, immunolocaliza-tion of TGF-β1 and histomorphometry of intramuscular collagen fibers were assessed over time of protocol (T0, T4, T8) on Tibial Anterior (TA) and Soleus (SOL). Results. Strength decreased after 4 weeks of training (T4) and was regained at T8 at mdx-T. The percentage of intramuscular collagen fibers area decreased at SOL muscle of mdx-T at T4 when compared to T0 (p=0,025) and TA of mdx-T had a lesser area at T8 when compared to TA of mdx-NT group (p=0,002). TGF-β1 was observed at the sarcoplasm of TA and SOL muscles of mdx-NT group, with an age-dependent change. Conclusions. Treadmill low-intensity training provoked dystrophic skeletal muscle adaptation of fibrosis and maintained grip strength of the mdx model.