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Introduction: Doxorubicin is one of the most important chemotherapy drugs for the treatment of solid tumors caused by the production of free radicals and the reduction of antioxidants to cardiac toxicity. The aim of this study is to evaluate the effect of pretreatment of three weeks of aerobic exercise on histological changes in the heart tissue of young and old rats by doxorubicin.
 
Materials & methods: In this study, 48 male rats were divided into two young and old age groups then each age group was also divided into three sub-groups: control, DOX, and exercise + DOX. Exercise groups ran on a treadmill for three weeks and five days a week at a speed of 15-17 meters per minute and time of 25-39 minutes. All groups received the solution of doxorubicin (20 mg kg) at 24 hours after the last exercise session. Finally biopsy was done at 48 hours after injection of DOX. Histological results were analyzed by a descriptive and qualitative method.
 
Findings: The preconditioning of aerobic exercise led to a significant reduction in severe edema and apoptosis induced by doxorubicin, and this reduction in tissue damage was more evident in the elderly.
 
 Discussion & conclusion: The findings indicate severe damage to the heart muscle in the elderly and the positive effects on doxorubicin induced apoptosis, and the effects of driving to apoptosis induced by doxorubicin. Also, the implementation of aerobic exercise pre-treatment with over a shorter period for elderly patients which were faced with the limitations of physical activity would be more appropriate and would lead to increasing the antioxidant protection role of heart tissue.