Hickson, R. C., Koziris, L. P., Chatterton, R. T., Groseth, R. T., Christie, J, M., & Unterman, T. G. (1998). Serum insulin-like growth factor-I (IGF-I) and IGF binding protein (BP) -1, -3 adaptations to training. Medicine and Science in Sports and Exercise, 30(5), Supplement abstract 989.

This study examined resting levels of serum IGF-I and IGFBP-1 and IGFBP-3 in competitive collegiate swimmers (M = 20; F = 9) at several time points (T1-pretraining, T2-after two months, T3-after four months (pre-taper), and T4-end of season).

• Serum IFG-I were increased in women from T2 to T3 and remained elevated at T4.
• In the men, IGF-I levels increase progressively with training and remained elevated at T4.
• Only in men at T4 was there a significant decline from T1 levels in IGFBP-1.
• IGFBP-3 in women was significantly higher from T1 to T2 and then remained at that level for T3 and T4.
• In men, IGFBP-3 was higher than T1 at T3 and T4.
• Serum testosterone levels did not change in women but were lower than T1 at T2 in men.
• Both men and women showed elevated serum cortisol levels over T1 at T4.

Serum growth factors changed as a response to training but gender differences and training-stage differences were not obvious.

Implication. Broad changes were observed in serum growth factors in swimmers over a training period of four months. No clear indications related to training stage or gender were evident.

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