Tehran University of Medical Sciences Health Technology Assessment in Action 2645-3835 8 4 2024 10 28 242 242 Seyed Morteza Tayebi Department of Exercise Physiology, Faculty of Physical Education and Sport Sciences, Allameh Tabataba'i University, Tehran, Iran Meraj Mirzaei Department of Exercise Physiology, Faculty of Physical Education and Sport Sciences, Allameh Tabataba'i University, Tehran, Iran Abbass Ghanbari Niaki Department of Exercise Physiology, Faculty of Physical Education and Sport Sciences, University of Mazandaran, Babolsar, Iran Rohoullah Haghshenas Gatabi Department of Exercise Physiology, Faculty of Physical Education and Sport Sciences, University of Mazandaran, Babolsar, Iran 2024 01 21 2024 05 25 Background: There have been few investigations into the impact of high-intensity interval training on blood rheology. Objectives: This study aimed to evaluate how high-intensity interval training conducted with different duration affects fibrinogen and plasma viscosity in sedentary young college men. Methods: For this study, 36 healthy male participants were selected and grouped based on their individual characteristics. The groups included a control group (n = 9), a 45-second training group (tr-45; n = 9), a 30-second training group (tr-30; n = 9), and a 15-second training group (tr-15; n = 9). The training regimen comprised six sessions over two weeks, with varying sets (4, 5, 6, 6, 7, 4 respectively) and durations of 15, 30, and 45 seconds for different groups. There was a fixed 4-minute rest interval between each set, with a consistent load of 0.6 on the Wingate cycle ergometer. Blood samples were collected 48 hours before and after the final session to analyze fibrinogen and plasma viscosity levels. Results: There were no significant differences between groups in plasma fibrinogen levels (F3, 32 = 2.303, P = 0.96). However, post-test analysis revealed a significant decrease in plasma fibrinogen in the tr-45 group (P = 0.027) compared to pre-test levels. Plasma viscosity did not significantly change between groups (F3, 32 = 0.651, P = 0.058), but there was a significant interaction between time and group (F3, 40= 4.43, P = 0.009). Post-test analysis showed a significant decrease in plasma viscosity in the tr-45 (P = 0.010), tr-30 (P = 0.002), and tr-15 (P = 0.003) groups, while it significantly increased in the control group (P = 0.004) compared to pre-test levels. Conclusions: The findings suggest that high-intensity interval training can effectively decrease blood rheology and factors such as fibrinogen and plasma viscosity, with the 45-second HIIT being more efficient. Therefore, incorporating this training into Physical Activity Programs could be beneficial for inactive men. https://htainaction.tums.ac.ir/index.php/hta/article/view/242 https://htainaction.tums.ac.ir/index.php/hta/article/download/242/164