RESUMEN
Maintaining the proportions of the myocytes, interstitium and collagen, is fundamental for myocardialfunction, This study examined the changes produced by aging in the densities of myocites, interstitiumand collagen of the left ventricular myocardium male Wistar rats and to see whether resistance exercise mayinfluence these changes. Three groups of animals were used: Control Group, sacrificed at 13 months of age,Sedentary Group, sacrificed at 16 months of age, and Trained Group, sacrificed at 16 months of age. Thevolume densities (Vv) of cardiac myocytes, interstitium, and collagen were determined in histological sectionsof the left ventricular wall. It was concluded that aging decreased the area occupied by myocytes with anincrease in the area occupied by the interstitium and collagen. Resistance exercise promoted the reversal ofcollagen accumulation, not influencing the effects of aging in the space occupied by myocytes and interstitiumin the myocardium.