IJCS | Volume 31, Nº5, September / October 2018

506 Feriani et al. Accumulated exercise in infarcted old rats Int J Cardiovasc Sci. 2018;31(5)505-512 Original Article cardiac event does occur, the vascular, neurohumoral and cardiopulmonary adaptations from exercise are effective in attenuating cardiometabolic complications and minimizing the deleterious effects of ischemia. 6 Experimentally, it has been shown that moderate intensity aerobic training prior to MI attenuates cardiac dysfunction and deterioration promoted by ischemia and preserves the contractile properties of cardiomyocytes, 7 as well as attenuates the loss of physical capacity and autonomic cardiac dysfunction. 8 One of the recommended ways to perform physical activity is accumulated aerobic training, which consists of performing the exercise in bouts over the course of a day, 9,10 and represents an interesting approach for individuals who have little time in their daily lives, as well as for the elderly. 11 This type of training can increase adherence to physical activity and, consequently, the number of people who follow the recommendations for physical exercise. 12 However, there is lack of knowledge concerning the possible protective effects of continuous or accumulated exercise performed prior to MI in aged rats. Thus, the aim of the present study was to evaluate the preventive effects of continuous and accumulated aerobic exercise on physical capacity, pulmonary congestion and ventricular weight in rats submitted to MI. Material and methods Experiments were performed in old male Wistar rats (24 months; ~475g), from the Animal House of the São Judas Tadeu University, São Paulo, Brazil. Rats were fed standard laboratory chow and water ad libitum. Rats were housed in collective polycarbonate cages, in a temperature-controlled room (22°C) under a 12h dark–light cycle (lights on 07:00 - 19:00 hours). The experimental protocol was approved by the Institutional Animal Care and Use Committee of the São Judas Tadeu University and the study was conducted in accordance with the National Institutes of Health guide for the care and use of Laboratory animals (NIH Publication number 96-23, revised 1996). The experimental design can be observed in Figure 1. At the beginning of the protocol, rats were assigned by simple random distribution to four groups, in which the sample sizewas defined by convenience: shamcontrol (C, n = 6); sedentary infarcted (S, n = 5); continuous aerobic exercise submitted to MI (CE, n = 6), and accumulated aerobic exercise submitted to MI (AE, n = 7). All experiments are described below in detail; however, in summary, groups were adapted to the treadmill and submitted to a maximal treadmill exercise test (MTET) to determine aerobic capacity and exercise training intensity. Trained animals - CE and AE - were submitted to aerobic exercise protocols for 1month, 13 whereas sedentary groups - C and S - were placed on the stationary treadmill at least three times a week to provide a similar environment. Twenty-four hours after the last session of exercise, or in a relative period for the sedentary groups, animals were underwent to MI (i.e., S, CE, and AE) or sham (i.e., C) surgeries. 1 day afterMI, the animalswere again submitted to the MTET. Four days after MI, 8 the animals were killed by decapitation in order to remove the organs. Maximal exercise test and aerobic exercise training Approximately one month before MI or sham surgeries, sedentary and trained rats were adapted to the treadmill (10 minutes per day; 0.3 km/h) for four days. All animals were submitted to a MTET to determine aerobic capacity and exercise training intensity at the beginning of the protocol, after aerobic ET protocol and post myocardial infarction. These evaluations were conducted by a blinded observer. MTET was based on a ramp protocol, which consisted of treadmill exercise with 0.3 km/h increments every 3 minutes, and finishedwhen the animals were not able to run. Our group previously demonstrated that MTET could detect differences in aerobic performance; since that, the maximal running speed achieved in the test has presented a good correlation with the maximum oxygen consumption. 14 After the adaptation period, the sedentary groups (i.e., C and S) underwent exercise only during the maximum running test. However, the animals were placed on the stationary treadmill at least three times a week to provide a similar environment. Aerobic training was performed on amotor treadmill (Inbramed TK-01, Brazil) at low intensity (30% of maximum running speed on MTET). Nevertheless, CE group performed the training on a continuous form for 1 h a day, while the AE group performed cumulatively (30minutes during the morning – 8:00-9:00 a.m. and 30 minutes during the afternoon – 16:00-17:00 p.m.). Both trainings were conducted 5 days a week for 4 weeks. Myocardial infarction Twenty-four hours after the last session of exercise, or in a relative period for the sedentary groups,