Keywords: Peripheral nerves, Muscle fibre, Physical exercise, Nerve injury, Silk proteinįor the histoenzymological study of the muscle fibres, classification according to the proposal of Brooke and Kaiser (1970) was used. Sericin biopolymer combined with swimming exercise did not affect plantar muscle function, submitted to experimental axonotmosis, whose contractile properties were altered by nerve injury. The area of fibres I, IIa and IIb remained constant between groups. The percentage of type I fibres was lower in the lesion group and there was no difference in fibres IIa and IIb between groups. Polymorphic neuromuscular junctions were detected in the groups, although without significant morphometric alterations of the area, major and minor diameters. The grip strength test did not show alterations in muscular functionality, and the control presented greater muscle mass in relation to the other groups, the same did not occur for muscle length. Afterwards, the animals were euthanised and the plantar muscle was dissected and submitted to histochemical and histoenzymological techniques.

Three days after sciatic nerve compression, the swimming and swimming and sericin groups were submitted to physical swimming exercise for 21 days. The application of sericin was done on the spot, 100 μL, shortly after nerve compression. Forty randomly divided adult rats were used in five groups of eight animals: control, injury, sericin, exercise, exercise and sericin. The aim of this study was analyse the effect of sericin associated with swimming exercise on the phenotype, innervation, and functionality of the plantar muscle of Wistar rats. Physical exercise may help maintain muscle properties and functional improvement after peripheral nerve lesion, which may be enhanced by using biocompatible substances, such as sericin.

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