The objective of this study was to investigate the effect of the association of different swimming program frequencies and diets on the characteristics of the anterior tibial muscle of 24 Wistar male rats. These rats were randomly assigned into three groups: untrained (control), trained group (two days/week) and trained group (five days/week). Each group was divided into two groups, which received one of the two normal or high calorie diets. After the training period, muscle samples were collected and frozen at -70ºC. Serial cryostat sections (8 mum) were sectioned and submitted to HE stain and to NADH-TR, m-ATPase (pH 4.4) and Sudan Black histochemical methods. The morphology was analyzed and the degree of fiber enlargement (on hypertrophy) evaluated using the lesser fiber diameter method. The data were submitted to analysis of variance (one way ANOVA). Muscle fibers were classified as SO, FOG and FG, presenting a mosaic distribution pattern, which were unchanged in all groups. Muscle fibers revealed a very low hypertrophy in all groups. Initial and final body weight were significantly different in trained groups. In the trained groups, especially in five days/week, muscle fibers revealed higher diameter, splitting and some internal myonucleus. Some atrophic fibers were observed and this observation was suggestive of denervation. The oxidative metabolism was higher in SO and FOG fibers. No significant alterations were observed in muscle contraction ability and the lipids content was intense in SO fibers, moderate in FOG fibers and low in FG fibers. The present study, with this protocol of two days/week and five days/week training caused different types of morphological lesions in fibers. The high calorie diet did not cause statistically significant results in comparison with the normal diet.
Anterior tibial muscle; Swimming; High calorie and normal diets
