ABSTRACT
         Background and Objectives: We studied effects of eight weeks of resistance training and IGF-1 injection on serum level of IGF-1, IGFBP-3 and IGF-1/IGFBP-3 ratio in Wistar rats.
          Methods: We randomly divided 28 male Wistar rats into four groups of saline-injected control (C), resistance training+saline injection (RS), resistance training+IGF-1 injection (RI) and IGF-1 injection (II). Resistance training protocol consisted of climbing a ladder (three days/week with 5 reps/3 sets) while carrying a weight suspended from the tail for eight weeks. IGF-1 and saline (1.5 µg/kg/day) were injected before and after exercise sessions. Serum IGF-1, IGFBP-3 and IGF-1/IGFBP-3 ratio and morphology of colorectal tissue were evaluated.
          Results: Serum IGF-1 level and IGF-1/IGFBP-3 ratio decreased in the RS group compared to the other groups (P< 0.05). Rats in the RS group had higher IGFBP-3 level than those in the II and RI groups (P< 0.05). IGF-1 injection had no effect on morphology of colorectal tissue.
          Conclusion: The resistance training reduces IGF-1 and increases IGFBP-3 levels, which might represent a link between resistance training and lower risk of colorectal cancer.
         Keywords: Exercise, Colorectal Neoplasms, Insulin-Like Growth Factor-1, Insulin-Like Growth Factor Binding Protein-3.