Post-myocardial infarction (MI) exercise has been employed to improve cardiac function. However, most studies have focused on endurance training (Et). Although Et has been reported to preserve cardiac function, evidence suggests that Et increases left ventricle (LV) interior dimensions as a result of albumin-induced plasma expansion. In contrast, strength training (St) induces concentric cardiac hypertrophy and improved cardiac function without causing ventricular dilation. Therefore, the purpose of this study was to investigate the effects of St on cardiac function and remodeling in rats with MI. MI was surgically induced in 7-week-old rats via ligation of the coronary artery. Survivors were assigned to two experimental groups, MI-Sed (No exercise; n = 9), MI-St (St; n = 10), with a Sham group (no MI, no St; n = 9). MI-St rats began training 1-week post-MI by climbing a ladder with weights for 10 weeks. Echocardiographic measurements were performed prior to, and following exercise training, while in vivo LV hemodynamic analysis was conducted at the end of the experimental period. Our data revealed that St induced shortening of the LV end-diastolic dimension in the MI-St group compared with the MI-Sed group (P < 0.05). The peak velocities of contraction (+ dP/dt max) and relaxation (- dP/dt max) were significantly greater in the MI-St group than the MI-Sed group (P < 0.05). These training effects contributed to the improved fractional shortening (%FS). Our results demonstrate that St may be beneficial for post-MI by attenuating LV dilation and concomitant cardiac dysfunction associated with MI.
Keywords: Cardiac function; Myocardial infarction; Rats; Strength training.