Background and Objectives:We studied the effects of eight weeks of resistance training and IGF -1 injection on serum level of IGF1, 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 lad der (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 IGF1 level and IGF1/IGFBP3 ratio decreased in the RS group compared to the other groups (P< 0.05). Rats in the RS group had higher IGFBP3 level than those in the II and RI groups (P< 0.05). IGF1injection had no effect on morphology of colorectal tissue. Conclusion: The resistance training reduces IGF-1 and increases IGFBP3 levels, which might represent a link between resistance training and lower risk of colorectal cancer.

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