The Effects of High-intensity Interval Training and Moderate-intensity Continuous Training on Autophagy, Cardiac Remodeling, and Heart Function in Aged Male Rats

Introduction: Aging is a physiological process that affects heart function. Training is known as a factor accelerating heart output, especially in aged individuals. In the present experimental study, the authors aimed to evaluate how high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) affect autophagy, cardiac remodeling, and cardiac function.  Methods: Twenty-four male Wistar rats, approximately 20 months old, were divided into three groups of control, HIIT, and MICT. The training programs lasted for eight weeks. Aerobic power and training capacity were also assessed. Two-dimensional echocardiography was also applied to assess cardiac indices. At the end of the experiment, tissue sampling of cardiac tissue was applied, and gene expression was assessed using the qRT-PCR technique. Data were analyzed using SPSS software, version 19. Results: After HIIT and MICT, no significant changes were detected regarding the animal weight. Also, mTORC1, Atg16, and Atg7 gene expression and ejection fraction (EF) and fractional shortening (FS) were accelerated in HIIT and MICT groups compared to control animals. Besides, the collagen type 3 (COLIII) gene expression, left ventricular end-diastolic diameter (LVEDD), and left ventricular end-systolic diameter (LVESD) showed a significant increase (p 0.05) in HIIT and MICT animals than control. Conclusion: Training can potentially improve cardiac output in older adults. Besides, HIIT seems more effective than MICT.