Introdution: Physical training causes functional and morphological changes in myocardium in response to regulatory adaptations same as Phosphatidilinositol-3-kinase (PI3K) changes. Present study aimed to experimentally investigate the effects of endurance and high intensity interval training on PI3K, structure and function of heart. Methods: 24 adultmale rats (weight 221.6 ± 11.4 grams) divided randomly into control, sham, interval and endurance groups(n=6). The endurance group swam for 12

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... /5 days per week. Also, the interval group swam 12 weeks/4 days per week. Twenty-four hours after the last exercise, echocardiography was done and 48h later, heart weight and left ventricle weight, and plasma for PI3K measurement (using ELAISA Reader) was taken. To assess the data, one-way ANOVA was utilized and Tukey-HSD was used to point out the place of significancy (α ≤ 0.05). Results: Findings showed that heart (p= 0.03) and left ventricle weights (p= 0.01), stroke volume (0.01), Left ventricular end diastolic volume (0.04), and ejection fraction (p= 0.02) after endurance and high intensity interval training were significantly more than the sham and control groups (p< 0.05). In addition, PI3K significantly increased (p= 0.00) in the endurance (6.58 ng/ml) and interval (6.67) rather than the sham (5.37) and control groups (4.07). Conclusion: It can be concluded that both the endurance and interval training schedules increase PI3K and they led to physiological hypertrophy of heart. Since the whole time of high intensity interval training is significantly shorter than that of the endurance training (~ 9%), it seems more beneficial to be executed.