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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