IJCS | Volume 31, Nº6, November / December 2018

615 Table 4 - Demonstration of uncorrected weights in relation to the tibial length; soleus muscle, EDL muscle, left ventricle and tibial length Uncorrected weights and tibial length Soleus (mg) EDL (mg) Left ventricle (mg) Tibial (cm) Groups CTR 250.1 311.0 939.1 4.2 DMC 131.6 97.3 604.5 3.7 DMS 144.2 111.4 655.0 3.7 DMT 134.5 102.8 600.5 3.7 Moura et al. Diabetic rats and aerobic training Int J Cardiovasc Sci. 2018;31(6)610-618 Original Article are not triggered and this prevents progressive weight loss. 22,23 As the ET was not able to promote better glycemic control, the improvement of body weight did not occur, either. The DMC group showed decreased exercise tolerance and the trained groups increased exercise tolerance after the ET protocol when compared with the DMC group. This result allows us to infer that DM1 had a negative influence on the exercise tolerance of the animal, and the ET, whatever the ergometer used, provided physiological adaptations to the diabetic animal, increasing exercise capacity. The DMT group was the only one with a significant improvement in exercise tolerance when compared to the results achieved before the experimental period. Adaptability and familiarity with the ergometer can explain this result, 24 as the exercise tolerance test was performed in the same ergometer in which the DMT group trained for 8 weeks. Regarding the skeletal muscles, the diabetic groups showed lower weights when compared with the CTR group. This result confirms the activation of biochemical mechanisms to increase energy bioavailability in the bloodstream, as well as the difficulties of supplying energy to maintain the cell, which is caused by the lack of insulin caused by DM1. 22 On the other hand, when we evaluated the cross- sectional area of the soleus and EDL muscles, we did not observe differences between the DMC and CTR groups. However, the ET on the treadmill was able to significantly increase the cross-sectional area of bothmuscles. ET leads to differentiation of muscle fiber types and the different types of fibers have different diameters. Although the soleus muscle has a predominance of type 1 fibers and the EDL muscle a predominance of type 2 fibers, there still exists a small percentage of other types of fibers that may influence this analysis. The histological technique used in this study did not allow us to differentiate between fiber types. 25,26 Furthermore, the biomechanics of movement in the ergometer should have favored the DMT group, as we analyzed agonist muscles. Muscle fibers of different types also have different metabolic profiles. Thus, the soleus muscle has an oxidative metabolism and, consequently, greater reserves of glycogen, whereas the EDL muscle has a predominantly glycolytic metabolism and lower bioavailability of glycogen. As expected, the DMC group showed lower glycogen content when compared to the CTR group in the EDL because they had not received insulin 23. In the soleus muscle, this decrease in muscle glycogen levels did not show statistical difference. Both ET protocols used in this study were able to increase glycogen content in both muscles when compared with the DMC group. This result corroborates the abovementioned data , where researchers claim that ET has the ability to increase the expression of the GLUT4 transporter. 21 This fact may have favored the entry of glucose into muscle cells. However, this action may not have been enough to affect serum glucose levels, which remained high even after the exercise training period. Possible explanations for the contrast observed in this study include the severity of STZ effects, which can vary between animals, and the intensity of the effort equivalent to metabolic transition, which may not be the most suitable one for obtaining the desired beneficial effects. 2 Regarding the analysis carried out in the heart, although glucose was found to be high in the DMC group and to stay high in the trained groups, we found no differences in the collagen volume fraction between the groups, corroborating the results of Stilli et al., 27 unlike the findings of other studies. 28,29 . Sears et al., 30 also induced DM1 with STZ at similar doses to those