IJCS | Volume 31, Nº5, September / October 2018

507 Figure 1 - Experimental design of the current study. Feriani et al. Accumulated exercise in infarcted old rats Int J Cardiovasc Sci. 2018;31(5)505-512 Original Article anaesthetized rats (80 mg/kg ketamine and 12 mg/ kg xylazine, i.p.) underwent surgical occlusion of the left coronary artery, which resulted in MI as described previously. 8 Briefly, after intubation, animals were positive-pressure ventilated with room air at 2.5 mL, 65 strokes/min with a pressure-cycled rodent ventilator (Harvard Apparatus, Model 683, Holliston, MA, USA). For induction of MI, a 2-cm left lateral thoracotomy was performed in the third intercostal space, and the left anterior descending coronary artery was occluded with a nylon (6.0) suture at approximately 1 mm from its origin below the tip of the left atrium. The C animals underwent the same procedures except that myocardial ischemia was not induced (Sham surgery). The chest was closed with a silk suture. Lung water content The lungswere removed andweighed (wetweight) and then placed in an oven for 24 hours at 80ºC. Posteriorly, the lungs were weighed again (dry weight). The water content (%H 2 O) of each lungwas defined by the equation: % H 2 O = (wet weight - dry weight) / wet weight x 100. 15 Organ and muscles relative weight The left ventricle (LV), right ventricle (RV), soleus and gastrocnemius were removed and weighed. The calculation of the organs relative weight of each rat was performed dividing the weight of each organ (in grams) by the body weight of each animal, and multiplying the result by 100. The result was then expressed in grams/100 grams of live weight (g/100 g l.w.). 16 Statistical analyses Statistical analyses were performed with GraphPad Prism software (Version 7.0 for Windows; GraphPad Software, Inc., SanDiego, CA). Data are reported as mean ± SEM. After confirming that all continuous variables were normally distributed using the Kolmogorov- Smirnov test, statistical differences between the groups were obtained by two-way ANOVA followed by the Bonferroni posttest. Statistical differences between the data measured over time were assessed using repeated- measures ANOVA. All tests were two-sided and the significance level was established at p < 0.05. Results At the beginning of the protocol, MTET indicated that physical capacity was similar in all groups (C = 0.9 ± 0.0 km/h; S = 0.8 ± 0.11 km/h; CE = 0.9 ± 0.09 km/h; AE = 0.9 ± 0.04 km/h). However, after the experimental protocol, CE and AE groups demonstrated higher MTET in comparison with the initial assessment (CE: +55%; AE: +33%), C group (CE: +100%; AE: +71%) and S group