Comparing the Effect of Two Methods of High-Intensity Interval Training (HIIT) and High-Intensity Continuous Training (HICT) on Damage and Antioxidant Indices of Liver in Male Wistar Rats

Background: Nowadays, one of the widely used training methods is high-intensity interval training (HIIT). In addition, researchers have stated that long-term, high-intensity training is associated with the production of free radicals in the body. Free radicals also damage liver cells, resulting in increased liver enzymes. Objectives: The objective of this study was to investigate the effect of HIIT, compared to high-intensity continuous training (HICT), on damage and antioxidant indices of the liver in male Wistar rats. Methods: Twenty-two adult male rats were randomly divided into three groups of control (n = 6), HIIT (n = 8), and HICT (n = 8). Training protocols included HIIT and HICT on a treadmill for eight weeks (five days in a week). Standard water and food were provided for rats ad libitum. Forty-eight hours after the last training session, blood and tissue samples were collected, and serum enzymes were measured by the methods recommended by the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) method. The level of enzyme activity of superoxide dismutase in the liver tissue was measured by Randox Commercial Kit (Cat. No. SD 126). One-way analysis of variance (ANOVA) and Tukey’s post hoc tests were used to analyze the data. Results: The results showed that eight weeks of HIIT and HICT had no effect on the alanine aminotransferase (ALT) level (P = 0.14), but eight weeks of HIIT significantly decreased the serum aspartate aminotransferase (AST) level compared to the control group (P = 0.04). The level of liver superoxide dismutase (SOD) enzyme activity significantly increased in the HIIT and HICT groups compared to the control group (P = 0.001). HICT also led to a significant increase in the SOD level compared to HIIT (P = 0.03). Conclusions: The research results suggested that eight weeks of HIIT led to a significant reduction in serum AST levels, and HIIT had a lower effect on the increased SOD activity in liver tissue compared to HICT. It might be stated that HIIT is safer than HICT, and it has fewer destructive effects on liver tissue.