Since participating in sports training is one of the best modalities to strengthen the bones and plays an important role in preventing bone injuries, the purpose of this recent research was to investigate the effect of an eight-week endurance training of running on positive and negative inclination on the biomechanical parameters of tibia bone in male Wistar rats. 15 Wistar rats with an approximate age of eight weeks and with a weight range of 180-200 grams were divided into 3 groups with an 8-week training protocol including: Control group (no activity), endurance training group in positive slope, endurance training group in negative slope. Three-point bending test was used to measure biomechanical parameters. The results showed a significant improvement in maximum mechanical resistance (F max), bone deformation and maximum energy absorbed to the maximum point of tibia bone strength in the endurance training group of running on a positive slope compared to the negative slope group and the control group. Moreover, it was observed that endurance training in positive and negative slopes had no significant effect on bone stiffness. Also, this type of endurance training in the negative slope caused a decrease in the mechanical parameters discussed in the research. Findings indicate the role of negative slope as a factor in reducing the quality of the biomechanical characteristics of bones in endurance training. It seems that endurance training of running in a positive slope can help improve bone indices. However, more considerations are needed in this field.