Introduction: Aging causes apoptosis in the heart. While the old heart is vulnerable to apoptosis, physical activity with different mechanisms can be effective in reducing apoptosis or inhibit it. The purpose of this study was to investigate the effect of moderate and high intensity interval trainings on some apoptotic indices of Bax and Bcl- 2 cardiomyocytes of old female rats. Methods: In this study, 21 aged female, postmenopausal Wistar rats (2 years old), were randomly divided into three groups: 1) control, 2) moderate intensity interval training (MIIT), and 3) high intensity interval training (HIIT). The training protocol performed consisted of two different intensities (MIIT and HIIT) of running on treadmill 3 sessions per week for 8 weeks. 48 hours after the last training session, the heart tissue was removed in order to analyze Bax, Bcl- 2 genes and Bax/Bcl- 2 ratio in the cardiomyocytes. Two-way analysis of variance was used to determine the main effect of training. In case of a statistically significant difference, Bonferroni post hoc test was used to determine the intergroup difference. Significance level for all data analysis was considered as p≤0.05. Results: Bax (p=0.0001) and Bax/Bcl- 2 ratio (p=0.001) gene expression was higher in the HIIT group in comparison with MIIT group nevertheless Bcl- 2 gene expression was higher in the MIIT group in comparison with the HIIT group (p=0.0001). Conclusion: Based on the present results, treadmill exercise with MIIT can support cardiac against apoptosis through the enhancement of Bcl- 2 expression in the heart. Therefore MIIT may be a beneficial method for preventing heart problems in the aging. Manuscript profile