تاثیر تمرین مقاومتی بر تغییرات عملکردی و هیستوپاتولوژیکی عضله پس از آسیب استرین مزمن در موش های صحرایی سالمند

Background and purpose: Repetitive strain injury (RSI) is accompanied by an increase in extracellular matrix (ECM), atrophy, and reduces the muscle power. Resistance training (RT) have potential positive effects on muscle function and morphology in elderly. This research examined the effects of eight week therapeutic resistance training on recovery of pathological changes after 6weeks chronic eccentric contraction. Materials and methods: Eighteen elderly male Wistar rats were divided into three groups (control, RSI-rest, RSI-RT). Two experimental groups underwent 6weeks (5 days/week) of fast velocity submaximal eccentric contractions while the control group was inactive. After two weeks rest, RSI-RT group performed 8 weeks resistance training and RSI-rest group was detrained for 8 weeks. Gastrocnemius muscle response was assessed by isometric force and muscle wet mass. Quantitative histopathological analysis was also done in all groups. Results: Gastrocnemius tissue of injured limbs showed increase in ECM and decrease in myofiber area and isometric force after 6 weeks RSI model in RSI-rest group, but muscle wet mass did not change. RT significantly improved isometric force, myofiber area percent but decreased non-contractile area percentage. However, pathological changes after RSI were not fully recovered by RT. Conclusion: Therapeutic Resistance training with an emphasis on concentric phase, low velocity and adequate rest can attenuate functional and histopathological changes in muscle after chronic strain injury in elderly rats.