INSULIN-LIKE GROWTH FACTOR AND ITS PROTEINS REMAIN RELATIVELY STABLE DURING ENDURANCE RUNNING TRAINING
Vukovich, M. D., Bjerke, K. J., Thum, M. K., Gauer, A. J., & Creer, A. R. (2009). Insulin-like growth factor 1 and insulin-like growth factor binding proteins 1 and 3 during a competitive college cross-country season. ACSM 56th Annual Meeting, Seattle, Washington. Presentation number 2415.
This study determined the effects of 10 weeks of training in male (N = 8) and female (N = 18) collegiate cross-country runners on insulin-like growth factor-I (IGF-I), insulin-like growth factor binding protein-1 (IGFBP-1), and insulin-like growth factor binding protein-3 (IGFBP-3). Active controls (M = 9; F = 10) served for comparison purposes. Blood samples were obtained at baseline, and at five and ten weeks. IGF-I, IGFBP-1, and IGFBP-3 were determined by ELISA. Diet records were obtained from all S for the three days prior to blood collection.
Weekly running distance remained relatively constant throughout the 10 weeks. Energy intake at baseline was higher in runners than in controls due to higher carbohydrate and protein intake. Energy, carbohydrate, and protein consumption remained constant for the duration of the study for all groups. Baseline IGF-I and IGFBP-3 were similar among the groups and did not change over time. Baseline IGFBP-1 was different among the groups. IGFBP-1 was lower (at week 5 and week 10) compared to baseline in male and female runners. There was no change in IGBP-1 in controls at week 5 or week 10.
Implication. A 10-week season of cross-country running had little effect on insulin-like growth factor-I and insulin-growth factor binding protein-3. The decline in insulin-growth factor binding protein-1 is unlikely related to negative energy or protein balance; as the runners remained weight stable. The change in insulin-growth factor binding protein-1 requires further investigation.
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