Time course responses of serum GH, insulin, IGF-1, IGFBP1, and IGFBP3 concentrations after heavy resistance exercise in trained and untrained men.

To investigate the effect of heavy resistance exercise on IGF-1 system, 19 healthy trained men and 15 healthy untrained men volunteered to participate in this study. The subjects were randomly divided into experimental and control groups. Subjects of experimental groups were forced to perform a heavy resistance exercise with the intensity of 70-80% of 1RM in selected movements. The blood samples were taken from all subjects four times; before (T1), immediately after (T2), 5 (T3), and 8 (T4) hours after exercise. Analysis of data showed that a session of heavy resistance exercise induced significant increase in GH at T2 (P < 0.05) and a significant decrease in insulin at T4 (P < 0.05) and a significant decrease in IGFBP3 at T4 (P < 0.05) in trained group. In untrained group, no significant change in any of the variables was observed. However, the procedure of response in variables was almost similar in two experimental groups. Although, the exercise did not appreciably affect IGF-1 levels, it decreased in all groups at length of time after exercise. In addition, the exercise did not have any notable effect on IGFBP1 levels over time. In conclusion, the findings of this study indicate that the intense resistance exercise can lead to changes in blood concentrations of IGF-1 system components which are observable in blood circulation over time and the amounts of changes depend on subjects' fitness levels and exercise variables.