Splenic morphologic changes induced by a strenuous and exhaustive training program in Wistar rats

Excessively intense physical training can compromise the functionality of the immune system and contribute to the appearance of symptoms associated with overtraining syndrome (OTS). The aim of this study was to analyze the splenic morphological changes in Wistar rats submitted to demanding training.

The animals were randomly assigned to 2 groups; control group (CG) and exercise group (EG), animals in the EG group were sacrificed after 1 (EG1) and 3 weeks (EG3) of training. The animals were stimulated to run on the treadmill (-20 °; from 25 m/min, with a progressive increase of 1.25 m/minute at each session; 1 hour/day) 6 days/week. Body weight, food intake, appearance of hair, behavior and ability of animals to perform the imposed work were assessed during the protocol. The spleen was collected for histological analysis and immunohistochemical identification of CD4⁺ T lymphocytes and CD8⁺ T cells and NF-kB transcription factor.

The protocol did not induce OTS, however, decreases were observed in areas of white pulp in EG3 in relation to the other groups. The training induced a decrease in splenic CD4⁺ T cells with an increase in CD8⁺ T cells. The training increased the expression of NF-κB P65 compared to sedentary animals.

Even without manifestation of OTS, strenuous physical training, alter the histological and immunological structures of the spleen, suggesting in part a compromise in the functionality of the immune system.