title: Effect of low-intensity aerobic exercise on insulin-like growth factor-I and insulin-like growth factor-binding proteins in healthy men.
abstract: Increased concentrations of circulating insulin-like growth factor-I (IGF-I) or IGF-I relative to IGF-binding proteins (IGFBPs) are associated with increased risk of developing several forms of cancer. Conversely, exercise is linked with reduced risk. This study aims to investigate the effect of a low-intensity exercise program on circulating levels of IGF-I, IGFBP-1, and IGFBP-3, in previously sedentary males. Fourteen healthy men participated in cycle ergometer training at lactate threshold intensity for 60 min/day, 5 days/week for 6 weeks. After aerobic training, insulin sensitivity improved by 20%, while fasting insulin levels decreased by 13%. Simultaneously, low-intensity aerobic training decreased the circulating levels of IGF-I by 9%, while IGFBP-1 levels increased by 16%. An interesting finding was that higher pretraining level of IGF-I was associated with greater decline in IGF-I with training. Insulin-sensitizing low-intensity aerobic exercise is thus considered to be an effective method for downregulating IGF-I and upregulating IGFBP-1 levels.
authors.affiliation: Laboratory of Exercise Physiology, Faculty of Health and Sports Science, Fukuoka University, Fukuoka 814-0180, Japan.
authors.forename: Yuichiro
authors.initials: Y
authors.lastname: Nishida
authors.forename: Takeshi
authors.initials: T
authors.lastname: Matsubara
authors.forename: Takuro
authors.initials: T
authors.lastname: Tobina
authors.forename: Munehiro
authors.initials: M
authors.lastname: Shindo
authors.forename: Kumpei
authors.initials: K
authors.lastname: Tokuyama
authors.forename: Keitaro
authors.initials: K
authors.lastname: Tanaka
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Tanaka