Insulin-like Growth Factor I In Skeletal Muscle After Weight-Lifting

By Ty Sevin, Aug 31, 2021

< Back to Benefits of Strength Training on Body Composition in Older Adults

Maria A. Fiatarone Singh, Wenjing Ding, Thomas J. Manfredi, Guido S. Solares, Evelyn F. O'Neill, Karen M. Clements, Nancy D. Ryan, Joseph J. Kehayias, Roger A. Fielding, and William J. Evans


To assess muscle remodeling and functional adaptation to exercise and diet interventions, 26 men and women (aged 72-98) underwent a quadriceps (vastus lateralis) biopsy before and after a 10-week study. These subjects were part of a study of 100 men and women (age 72-98) who participated in one of four treatment groups including; a placebo control condition, progressive resistance training, multi-nutrient supplementation, or both resistance training and supplementation.


Analysis of biopsies showed Type II atrophy, Z band, and myofibril damage were present at baseline. Combined resistance training and nutritional supplementation increased strength by 257+ 62% (P = 0.0001) and type II fiber area by 10.1+ 9.0% (P = 0.033), with a similar trend for type I fiber area (+12.8 + 22.2%). Resistance training alone was associated with a 2.5-fold increase in neonatal myosin staining (P = 0.0009) and an increase of 491 + 137% (P<0.0001) in IGF-I staining. Ultrastructural damage (a step in the remodeling process) increased by 141 + 59% after exercise training (P = 0.034). Strength increases were largest in those with the greatest increases in myosin, IGF-I, ultrastructural damage, and caloric intake during the trial.


This study provides the first evidence of skeletal muscle remodeling in response to resistance training in frail individuals of extreme old age. Age-related sarcopenia appears largely confined to type II muscle fibers suggesting that interventions aimed specifically at stimulating type II fibers (e.g., contractions demanding high force output, i.e. power) may be most effective in the prevention and treatment of sarcopenia. Muscle hypertrophy was linked to higher caloric intake suggesting that adequate energy balance is a critical component of treating sarcopenia with exercise in frail elders.

Keiser Equipment Used

Leg press and leg extension 

Published in the American Journal of Physiology-Endocrinology and Metabolism, 1999; vol. 277, issue 1, E135-E143

Link to Original Research

About the author

Ty Sevin

Director of Human Performance, Education and Research

Articles by Ty Sevin >

With over 25 years of coaching experience at both the collegiate and Olympic levels, Ty Sevin is one of the most influential track and field coaches in the country. Ty has worked for the United States Olympic Committee, serving as the Director of the Track and Field Residency Program at the USOC Olympic Training Center in Chula Vista, CA. He has also served as an assistant coach for Team USA on three separate occasions, for both the men’s and women’s teams. Ty himself was a four-time U.S. Olympics Trials qualifier in javelin. Ty most recently spent four years as the Associate Head Coach at the University of Texas at Austin for both the men’s and women’s track and field teams. Prior to that, he led the men’s and women’s track and cross-country teams at the University of New Orleans and McNeese State.

Currently, Ty applies his vast industry experience to the role of Director of Human Performance, Research and Education for Keiser Corporation, where he consults with college and professional sports teams regarding the utilization of Keiser strength equipment. He is also responsible for creating educational curriculum relating to human performance and overseeing Keiser research projects