Background: Some researchers attributed the positive effects of exercise training on secretion of different myokines from skeletal muscles. Acute exercise lead to changes in gene expression and phosphorylation that stimulates muscular adaptation. However, one bout exercise isn’t adequate to change muscle phenotype and phenotypic adaptation to training consists of aggregation stimulation of one bout exercise sessions Decorin is new discovered myokine that its changes in response to exercise such as high intensity interval exercise (HIIE) is unknown. It seems that Decorin has effects on skeletal muscle hypertrophy. Therefore, the aim of present study was investigated the effect of one bout high intensity interval exercise (HIIE) on serum levels of decorin and IGF-I in active young male. Materials and Methods: For this purpose, 10 active young males with mean age of 25.4±2.36 voluntary participated in this study. The subjects took part in HIIE protocol in 10 am and after 3 hours. HIIE protocol consisted of four minutes' intervals with 90-95 percent of maximum heart rate that between each interval, 3-minute active recovery with 60-70 percent of maximum heart rate performed. The subjects heart rate during HIIE protocol was monitored by polar belt. Blood samples were collected immediately after exercise, subsequently IGF-I and decorin levels were measured by ELISA method. In order to data analyzed, SPSS software version 24 and paired t test were used and significantly level was considered p<0.05. Results: The results indicated that decorin and IGF-I increased significantly after exercise (p≤0/05). Conclusion: It seems that some HIIT-induced adaptations partly are related to increase in decorin levels. Manuscript profile