Prior Aerobic Exercise Training Fails to Confer Cardioprotection Under Varying Exercise Volumes in Early Post-Infarction Cardiac Remodeling in Female Rats.

Background: There is no information on how the dose of exercise training prior to myocardial infarction (MI) affects cardioprotection. Objective: This study aimed to evaluate the cardioprotective role of different volumes of exercise training prior to MI. Methods: Wistar female rats were allocated to one of the following groups: SHAM (not trained and undergoing simulated MI surgery), NT+MI (untrained and undergoing MI surgery), T60+MI (trained 60 min per session and undergoing MI surgery), T90+MI (trained 90 min per session and undergoing MI surgery), and T180+MI (trained 180 min per session and undergoing MI surgery). The training protocol was performed in a swimming pool for eight weeks. On the seventh day after MI, the animals underwent left ventricular (LV) structural and functional evaluation and were euthanized for molecular analyses. Results: Exercise training groups had greater VO(2)peak and LV mass than did the SHAM group. The MI size did not differ statistically among the experimental groups. Compared with the SHAM group, all the MI groups presented a lower LV shortening fraction. LV systolic pressure was significantly lower in the T60+MI group than in the SHAM and T180+MI groups. The +dP/dt of the LV was significantly lower in the NT+MI, T60+MI, and T90+MI groups than in the SHAM group. We did not find significant changes in the inflammatory mediators and oxidative stress markers as well as proteins involved in calcium handling. Conclusions: Exercise training prior to MI enhanced cardiorespiratory fitness and induced LV hypertrophy, however, regardless of volume, was unable to counteract the detrimental effects of MI.