Treadmill Low-Intensity Training Mediates Fibrosis and Maintains the Function of Dystrophic Muscle: Understanding the Effects Over Time

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, immunolocalization of TGF-beta1 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-beta1 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.