Background and Objectives: Skeletal muscle mass depends on the balance between synthesis and degradation of muscle protein, which changes with aging and disease. The aim of the present reserch was to examine the effects of two exercise training protocols on alterations of some genes involved in pathways of protein synthesis and degradation in order to achieve a more effective training program in case of pathological conditions, aging process, and improvement of athletic performance. Methods: In this experimental study, 8 weeks old Wistar rats, were randomly divided into three groups of resistance training, highintensity interval training, and control. To examine gene expression, 48 hours after the last exercise session, the Soleus muscles were dissected and stored at-80C. Between-group differences, were analysed using parametric and non-parametric tests at the significance level of α˂0.05. Results: Compared to the control group, the increased expression of AKT and Rps6kb1 genes, was significant in both training groups (especially resistance group). Moreover, the gene expression related to the protein degradation signaling pathway, (MuRF1 and Map1LC3a), were suppressed by both training protocols, especially high-intensity interval training group and were confirmed by Western blotting analysis. Conclusion: Given the fact that the protein synthesis-related gene expression was increased by resistance training and protein degradation-related gene expression was suppressed by high-intensity interval training, the practical application of the two protocols can be considered simultaneously in order to reduce muscle atrophy in pathological conditions, aging, as well as to increase muscle strength to improve athletic performance.

Background: Muscle loss occurs in some conditions such as aging, sarcopenia, and cancer. The interaction between protein synthesis and degradation signaling components induced by high-intensity interval training (HIIT) is not well studied. Objectives: The purpose of the present study was to simultaneously examine the effect of eight-week HIIT on the gene expression of both signaling components. Methods: Sixteen male Wistar rats were randomly assigned to HIIT and non-exercise control groups. The HIIT group ran on a treadmill, five days/week for eight weeks, with 0º slope, including five interval sets of high and low intensity. Forty-eight hours after the last exercise session, dissected soleus muscles were stored at -80°C for later analyses. Results: The gene expression of Akt1, mTORC1, and S6K1 were increased in the HIIT group compared with the control group (All P ≤ 0.031) concomitant with the suppression of eIF4EBP1. The results of the S6K1 and eIF4EBP1 mRNA were also confirmed by the Western blotting. According to the inhibitory effect of Akt1, the gene expressions of FoxO3a and, consequently, MuRF1 and LC3A were significantly inhibited (All P ≤ 0.003). Western blot analysis did not confirm the LC3A protein expression, which may underline the role of LC3A in autophagy to promote cell survival. Conclusions: The intensities and durations of the exercise training protocol are sufficient to increase protein synthesis signaling components and especially inhibit the atrophy-related gene expression, which may lead to attenuating muscle loss and increasing muscle mass. Accordingly, it may be considered for rehabilitation and/or prevention of some conditions such as sarcopenia and cachexia.