Muscle mechanical properties of adult and older rats submitted to exercise after immobilization

OBJECTIVES: To describe the effects of immobilization, free remobilization and remobilization by physical exercise about mechanical properties of skeletal muscle of rats of two age groups. METHODS: 56 Wistar rats divided into two groups according to age, an adult group (five months) and an older group (15 months). These groups were subdivided in: control, immobilized, free remobilized and remobilized by physical exercise. The pelvic limb of rats was immobilized for seven days. The exercise protocol consisted of five swimming sessions, once per day and 25 minutes per session. The gastrocnemius muscle was subjected to tensile tests, and evaluated the properties: load at the maximum limit, stretching at the maximum limit and stiffness. RESULTS: The immobilization reduced the values of load at the maximum limit and the remobilization protocols were not sufficient to restore control levels in adult group and older rats. The stretching at the maximum limit differs only in the older group. CONCLUSIONS: The immobilization reduces the muscle's ability to bear loads and exercise protocol tends to restore the default at control values in adult and older rats. The age factor only interfered in the stretching at the maximum limit, inducing a reduction of this property in the post-immobilization. Level of Evidence II, Investigating the Results of Treatment.