Background and aims: Endurance training has a potential ability to prevent breast cancer by strengthening the immune system and reducing inflammation, and can reduce cachexia which is effects of cancer in advanced stages. This study aims to investigate the effect of endurance training with moderate intensity on the serum levels of TNF-α and weight of the mice suffered from breast cancer.

Methods: 24 female BALB/c mice were randomly allocated to 3 groups: negative control
(Rest-Healthy); positive control (Rest-Tumor) and experimental (Exercise-Tumor) groups. The experimental group carried out the continuous endurance exercise 5 days per week for 12 weeks. Training intensity was begun from 15.4 meter per minutes in the first week and gradually raised up to 23.8 meters per minutes in the last week. 24 hours after the end of training program, the 4T1 cancer cell line was injected subcutaneously to mice in positive control and experimental groups. After tumor formation, TNF-α concentration was measured by ELISA. The weight of mice was measured regularly from the beginning to the end of the study after each two-week training period subsequently.

Results: The Mean of TNF-α in the experimental group as compared to the positive control decreased significantly (P=0.030), but there was no significant difference between experimental and negative control groups. The mean of weight of rats in the experimental group was significantly lower than both positive and negative control groups during tumor formation and after two weeks was lower compared to positive control group.

Conclusion: It seems that participating in moderate-intensity training can play a role by decreasing the cytokine TNF-α and cachexia to prevent breast cancer.