The effects of strength vs. endurance exercise training on cardiac function and remodeling in post-myocardial infarction rats




Garza, Michael Anthony

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Increased plasma volume (PV) is consistently observed in patients with myocardial infarction (MI), and contributes to the progressive decline in cardiac function by exacerbating left ventricular (LV) dilation; however, compelling evidence suggests that endurance exercise training, despite eliciting a marked increase in PV, beneficially preserves post-MI cardiac function. Contrarily, strength exercise training, which promotes concentric myocardial hypertrophy and has no effect on PV, may be more therapeutic in post-MI applications; therefore, the purpose of this study was to investigate for the first time the effects of strength vs. endurance exercise training on myocardial function and remodeling in post-MI rats. MI was surgically induced on 7-wk-old Sprague-Dawley rats by ligation of the coronary artery. The survivors were assigned to 4 groups (n=10/group): Sham (no MI, no exercise), MI-Sed (MI, no exercise), MI-End (MI+endurance exercise), and MI-St (MI+strength exercise). Endurance and strength exercise training using a rodent treadmill or an 85¢ª inclined ladder, respectively, began 1-wk post-MI and lasted for 10-wks. Echocardiogram measurements (Echo) were performed on the day prior to initiation of exercise training and at the end of exercise training, while in vivo pressure-volume analysis (PVAN) were conducted at the end of exercise training. Echo data revealed that although fractional shortening (FS%) was well preserved in both exercise trained groups compared to the MI-Sed group, LV end-diastolic dimension was significantly lower in the MI-St group compared to the MI-End group (1.075¡¾0.01 vs. 1.184¡¾0.02 cm, p<0.05); furthermore, PVAN data illustrated that dP/dt max values were significantly higher in the MI-St than in the MI-End group (7124.4¡¾293.9 vs. 5888.0¡¾176.8 mmHg/s, p<0.05). Lastly, post-MI strength training significantly elicited a concentric hypertrophic response in the LV posterior wall (p<0.05). Together, these results suggest that strength training may be more beneficial than endurance training at preserving post-MI cardiac function; in addition, this study demonstrated that post-MI strength training significantly attenuates LV dilation without causing any observable adverse effects.


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endurance exercise, exercise, Myocardial infarction, rats, remodeling, strength exercise



Health and Kinesiology