IGF-1 bioavailability is increased by resistance training in older women with low bone mineral density.
We investigated if long-term resistance training would increase insulin-like growth factor-1 (IGF-1) bioavailabilty at rest in older women (68+/-1 years) with low bone mineral density. IGF-1 levels were significantly lower (P<0.05), and insulin-like growth factor binding proteins -1 and -3 (IGFBP-1 and IGFBP-3) significantly higher than an age-matched healthy normal group. Resistance training resulted in significant (P<0.05) increases in repetition maximums across all exercises (range 41-78%). Resting IGF-1 levels were significantly (P<0.05) elevated (70%) by the resistance training whereas no significant changes occurred in IGFBP-1 and IGFBP-3 levels. IGFBP-1/IGF-1 and IGFBP-3/IGF-1 ratios were significantly decreased (approximately - 50%) as a result of resistance training (P<0.05). Thus, IGF-1 bioavailability was increased as a result of resistance training induced increases in IGF-1 levels in older women with low bone mineral density. These alterations in the IGF-1 system may be contributing to the significant strength gain observed with the resistance training in this population.
Parkhouse
W S
WS
Metabolic Biochemistry Laboratory, School of Kinesiology, Simon Fraser University, Burnaby, BC, Canada. parkhous@sfu.ca
Coupland
D C
DC
Li
C
C
Vanderhoek
K J
KJ
D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000097:blood*; D001682:Biological Availability; D015519:Bone Density / Q000502:physiology*; D005081:Exercise Therapy; D005260:Female; D006801:Humans; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000097:blood; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008875:Middle Aged; D014891:Weight Lifting / Q000502:physiology
D018970:Insulin-Like Growth Factor Binding Protein 1; D018972:Insulin-Like Growth Factor Binding Protein 3; D007334:Insulin-Like Growth Factor I