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


METHODS
Center for Exercise Science, University of Florida, Gainesville.


METHODS
Sixty-two men and women (mean age = 68.1).


METHODS
A 6-month, 3-day/week program of low-intensity RT (LEX), high-intensity RT (HEX), or no exercise (CON).


METHODS
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.
Borst
Stephen E
SE
Department of Exercise and Sport Sciences, University of Florida, Gainesville, Florida, USA. sborst@pharmacology.ufl.edu
Vincent
Kevin R
KR
Lowenthal
David T
DT
Braith
Randy W
RW
D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D015444:Exercise / Q000502:physiology*; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000097:blood; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000097:blood*; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood*; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012737:Sex Factors; D013002:Somatomedins / Q000032:analysis*; D013739:Testosterone / Q000097:blood; D013997:Time Factors; D014891:Weight Lifting / Q000502:physiology*
D018970:Insulin-Like Growth Factor Binding Protein 1; D018972:Insulin-Like Growth Factor Binding Protein 3; D013002:Somatomedins; D013739:Testosterone; D006854:Hydrocortisone