Background and Objective: Scientific evidence reveals that the density of skeletal muscle microcirculations decreases in the patients with chronic heart failure. Therefore, this study aimed to determine the impact of submaximal aerobic exercise training on restoration of fast/slow-twitch muscle fibers microcirculation in rats with myocardial infarction. Methods: In this experimental study, 30 male infarcted Wistar rats were randomly divided into three groups of sham (N=10), control (N=10) and exercise (N=10), four weeks after surgery (blockage of anterior descending artery). Daily aerobic exercise included running on a treadmill for 10 weeks (5 times a week) at a speed of 17 m/min within 10 to 50 minutes. The animals were anesthetized and then sacrificed with chloroform, 48 hours after the last training session. The microcirculation density of soleus (SOL) and gastrocnemius (Gw) muscles was evaluated by immunohistochemistry assay. Results: Capillary density and capillary to SOL muscle fiber ratio significantly increased in response to exercise training. However, capillary density, capillary to Gw muscle fiber ratio and Gw muscle arteriolar density of Wistar rats with chronic heart failure were not significantly affected by the exercise program. Moreover, arteriolar density of Gw muscle increased significantly after the exercise program. Conclusion: The ten-week aerobic exercise might non-uniformly improve the SOL and Gw muscles microcirculation in rats with chronic heart failure by increasing capillary density and capillary to fiber ratio in the SOL muscle and increasing the arteriolar density of the Gw muscle.
