Journal of Morphological Sciences
Journal of Morphological Sciences
Original Article

Effects of long-term physical exercise in the skeletal muscles of rats


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Introdcution: The effects of long-term physical exercise in the skeletal muscles were evaluated. Methods: 30 male Wistar rats, 25 days old each, were divided in 2 groups: trained (TG, n=21) and sedentary (SG, n=9). The TG group was subdivided in 3 groups: TGI, TGII and TGIII, n=7 in each group, and the SG was also subdivided in 3 groups: SGI, SGII and SGIII, n=3. The animals of the TG (I, II and III) performed running exercise on a electric running machine for 3, 6 and 9 weeks respectively. The animals of the sedentary groups remained without any exercise. After the experimental period the soleus (SOL), the extensor digitorum longus (EDL) and the plantaris (PL) muscles were extracted, weighed and analyzed by the histochemichal technique of mATPase to observe possible changes. Results: The TGIII showed a significant increase in the absolute values of muscle weight when compared to the TGI and TGII. There was an increase in the distribution of type I fibers and a decrease in types IIC and IIA in the SOL muscle. The EDL muscle showed an increase in IIA fibers and a decrease in IID IIB types. As for the PL muscle there was an increase in types IIA and IIAD and a decrease in IID type fibers. Conclusion: Physical exercise causes changes in the distribution of fiber types in the skeletal muscles of rats and confirms the capacity of the fibers to adapt to the requirements of the proposed physical exercise in order to achieve a better performance.


fiber types, physical exercise, muscle plasticity


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