Biomechanical effects of immobilization and rehabilitation on the skeletal muscle of trained and sedentary rats

Because of the scarcity of information about the comparison of training to sedentarism beforehand immobilization and rehabilitation through muscle mechanical properties, the present work investigates this theme. Seventy rats were divided into 7 groups: 1-control (C); 2-trained (T); 3-sedentary (S); 4-trained and immobilized (TI); 5-sedentary and immobilized (SI); 6-trained, immobilized and rehabilitated (TIR); 7-sedentary, immobilized and rehabilitated (SIR). Interventions: Swimming training; Sedentarism (reduced size cages); Cast immobilization (pelvic limb) and water rehabilitation. Load at the limit of proportionality (LLP), maximum limit load (MLL) and stiffness (St) were the mechanical properties determined after a mechanical test of traction of the gastrocnemius. The training improved all mechanical properties when compared to sedentarism. After immobilization, LLP and MLL were reduced in TI and SI. However, there was no difference in St between C and TI. Additionally, TI showed improved MLL when compared to SI. The comparison of TI and TIR showed significant melioration in all properties after remobilization. SIR showed an improvement only in MLL when compared to SI. Significant melioration in LLP and St was observed in TIR compared to SIR. We demonstrated that the training before immobilization and rehabilitation had a positive effect on the muscle mechanical behavior compared to sedentarism. This analysis is of fundamental importance because it helps characterize the muscle tissue under different functional demands.