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

Abstract

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 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.

Conclusions: We conclude that the increases in strength and endurance caused by RT were not mediated by increases in circulating IGF-I, IGFBPs, or testosterone.