Exercise-induced insulin-like growth factor I system concentrations after training in women.

AB Introduction: This study examined the effects of short-term physical training on the acute hormonal response (i.e., growth hormone, total and free insulin-like growth factor I [IGF-I], and IGF binding proteins [IGFBP]-1, IGFBP-2, and IGFBP-3) to resistance exercise (RE) in women. Methods: Forty-six women (20.3 +/- 0.3 yr, mass = 64.1 +/- 7.3 kg, height = 165.7 +/- 1.0 cm) were randomly assigned to an endurance training (E), resistance training (R), combined training (R + E), or control (C) group for 8 wk. Subjects completed a standardized bout of RE (six sets of back squats at 10 repetition maximum) before and after training. Blood samples were obtained at rest (PRE), after the third set, immediately postexercise (POST), and at 15 min and 30 min after exercise. Results: Acute RE significantly increased (P < 0.05) serum growth hormone (mean +/- SD; change from PRE to POST = +10.9 +/- 7.5 [mu]g[middle dot]L-1), total IGF-I (+66.1 +/- 25.4 [mu]g[middle dot]L-1), IGFBP-1 (+2.5 +/- 3.1 [mu]g[middle dot]L-1), IGFBP-2 (+86.0 +/- 86.8 [mu]g[middle dot]L-1), and IGFBP-3 (+0.69 +/- 0.25 mg[middle dot]L-1) concentrations and decreased free IGF-I concentrations (-0.14 +/- 0.21 [mu]g[middle dot]L-1). After 8 wk of training, total IGF-I concentrations were significantly increased (change in POST concentrations from week 0 to week 8 = +82.5 +/- 120.8 [mu]g[middle dot]L-1), and IGFBP-1 concentrations were significantly decreased (-6.7 +/- 13.6 [mu]g[middle dot]L-1) during exercise in groups that participated in resistance training (R and R + E); no significant changes were seen after E or C. Conclusions: Participation in resistance training increased total IGF-I and reduced IGFBP-1 concentrations during acute RE, indicating exercise mode-specific adaptations in the circulating IGF-I system.