Effects of resistance training on insulin-like growth factor and its binding proteins in men and women aged 60 to 85

OBJECTIVES: 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. SETTING: Center for Exercise Science., University of Florida, Gainesville. PARTICIPANTS: Sixty-two men and women (mean age 68.1). INTERVENTION: A 6-month, 3-day/week program of low-intensity RT (LEX), high-intensity RT (HEX), or no exercise (CON). MEASUREMENTS: 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. RESULTS: RT caused significant increases in I-repetition maximum (1RM) strength and peak oxygen consumption (V0(2peak)), which we have reported separately. Currently, we report that RT had no effect on the r.-sting serum concentrations of IGF-1, 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. CONCLUSIONS: We conclude that the increases in strength and endurance caused by RT were not mediated by, increases in circulating IGF-1, IGFBPs, or testosterone.