Background: Skeletal muscle has the ability to adapt to several stimuli, such as contractile activity as well as direct and indirect damage. Aquatic therapy has been used in the rehabilitation of musculoskeletal disorders. In addition, it has demonstrated positive results in the therapeutic process and preventing several diseases.. Objective: The aim of the present study was to analyze the effect of swimming on the expression of the myogenic regulatory factors MyoD and myogenin during the skeletal muscle repair process in rats following cryoinjury. Methods: Forty Wistar rats were randomly divided into four groups: 1) Control; 2) Sham -non-muscle damaged, submitted to procedure for exposure of the tibialis anterior (TA) muscle; 3) Cryoinjured; and 4) Cryoinjured and submitted to swimming. Analyses were carried out at 7, 14 and 21 days. Cryoinjury was performed with two applications of the flat end of a metal rod previously cooled in liquid nitrogen directly to the belly of the TA muscle. The protocol consisted of 90-minute swimming sessions six times a week. At the end of the protocol, the animals were euthanized and the TA muscles were removed. Total RNA was extracted using the TRIzol reagent. Next, cDNA was obtained to perform real-time PCR using specific primers for MyoD and myogenin. Results: The results showed a reduction in the expression of myogenin in the groups cryoinjury with p≤0.01and without p ≤0.01 swimming after 7 days, and in group cryoinjury with swimming (p≤0.05) after 14 days respect to the control groups and "sham", respectively. There were no differences between groups cryoinjury with (p> 0.05) and without (p>0.05) swimming. Regarding the expression of MyoD there was no difference between the groups. Conclusion: Swimming did not affect the expression of myogenic regulatory factors during the skeletal muscle repair process in rats following cryoinjury.

O objetivo do estudo foi investigar a influência da natação sobre as alterações morfológicas do músculo esquelético em processo de reparo após criolesão. Foram usados 45 ratos divididos em cinco grupos: controle (n=5); sham (n=5), adaptação (n=5), criolesionados e tratados com natação sacrificados após 7, 14 e 21 dias (n=15); criolesionados e sem tratamento aquático sacrificados após 7, 14 e 21 dias (n=15). As sessões de natação foram realizadas 6 vezes por semana com 90 min de duração cada. Ao término do protocolo os animais foram sacrificados e a análise morfológica da área da lesão foi realizada. A análise morfológica semiquantitativa demonstrou que os músculos do grupo controle apresentaram aspecto histológico normal. O grupo sham apresentou edema, mionecrose e infiltrado inflamatório em grau 1. Nos grupos 7, 14 e 21 dias, não existiram diferenças estatisticamente significativas nas 4 etapas de remodelamento tecidual avaliadas (infiltrado inflamatório, edema, necrose e fibras musculares imaturas) entre os grupos lesionados quando comparados aos grupos com lesão e tratamento aquático. Em conclusão, foi possível verificar que a natação não causou alterações morfológicas durante o reparo do músculo esquelético após criolesão.