Effects of Resistance Training on Insulin‐Like Growth Factor and its Binding Proteins in Men and Women Aged 60 to 85

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Abstract
We have reported that resistance training (RT) elevates insulin-like growth factor (IGF-I) in healthy young adults. Our goals were to determine whether RT produces a similar effect in the healthy older persons and to determine the effects of low- versus high-intensity RT on hormonal status. Center for Exercise Science, University of Florida, Gainesville. Sixty-two men and women (mean age = 68.1). A 6-month, 3-day/week program of low-intensity RT (LEX), high-intensity RT (HEX), or no exercise (CON). Before and after training, blood was drawn for hormone analysis. IGF-I, IGF binding protein-1 (IGFBP-1), and IGFBP-3 were measured at rest. Testosterone and cortisol were measured at rest and immediately after exercise. RT caused significant increases in 1-repetition maximum (1RM) strength and peak oxygen consumption (V02peak), which we have reported separately. Currently, we report that RT had no effect on the resting serum concentrations of IGF-I, IGFBP-1, IGFBP-3, testosterone, or cortisol. Acute resistance exercise caused no change in circulating testosterone in men or women but did cause a significant elevation of cortisol in the HEX group. This increase in cortisol was blunted as a result of training. We conclude that the increases in strength and endurance caused by RT were not mediated by increases in circulating IGF-I, IGFBPs, or testosterone.