Background: Exercise programs are related to the anabolic function of GH/IGF-I axis.
Objective and hypotheses: To analyse IGF-I, IGFBP-3 and ALS serum concentrations in adolescent swimmers at different stages of training season, and compare them with physical performance and body composition.
Method: Nine male athletes, aged 1619 years, who trained regularly throughout the season, were studied. IGF-I, IGFBP-3 and ALS were recorded before and after standardized training sessions during different stages of a training season (extensive, intensive, tapering). Aerobic endurance in freestyle, anaerobic fitness in tied swimming (Peak Force and Average Force), weight, fat-percentage and lean body mass were analysed at the different stages of training.
Results: IGF-I was sensitive to the acute and chronic effects of training, exhibiting biphasic behaviour throughout the season. Catabolic phase was characterized by reduction in IGF-I levels during the intensive stage (ΔIGF-I: −43±47 ng/ml; P<0.05) while anabolic phase was marked by an increase in post-training serum IGF-I levels during the tapering stage following similar basal concentrations at the different stages of training (319±40, 298±36 and 359±94 ng/ml; P<0.05). IGFBP-3 was sensitive to the chronic effects, with reduction in post-training serum levels during the intensive stage and an increase during the tapering stage (4.7±0.7, 4.6±0.4 and 5.0±0.7 mg/l; P<0.05). No difference (P>0.05) was observed between pre-/post-training IGFBP-3 levels (ΔIGFBP-3) at the different stages. ALS remained unchanged throughout the season. Peak Force (25.0±6.3, 24.2±5.7 and 28.5±6.5N; P<0.05) and Average Force (10.3±3.6, 8.8±1.8 and 14.7±1.8N; P<0.05) followed IGF-I and IGFBP-3 variations, with a decrease during the intensive stage and an increase during the tapering stage (P<0.05). Body composition and cardiorespiratory condition did not change throughout the season.
Conclusion: Serum IGF-I and IGFPB-3 concentrations have proven to be sensitive markers of training status and, thus, may be used as guide for the challenging task of modulating training intensity in young athletes.
10 - 12 Sep 2016
European Society for Paediatric Endocrinology