2023, Vol. 10, Issue 1, Part D

Purpose: The aim of this study was to verify the kinetics of the concentrations of different components of the GH/IGF-I axis and to monitor the motor performance of adolescent soccer players during a competitive season.

Methods: Eleven U-15 male athletes from a Brazilian soccer team participated in this study. The participants were evaluated in 3 moments during seven months of season: before (M1), during (M2), and after the season (M3). In all assessment moments, the following field tests were applied: Léger, RAST, 30m velocity, six jump, and agility T-tests. In addition, before and after a standard training session (STS), the kinetics of the GH, IGF-I, and IGFBP-3 were analyzed via venous blood samples.

Results: IGF-I levels were reduced post-STS in M3 (p=0.04). The variation in IGF-I concentrations post-STS was higher in M2 compared to M3. IGFBP-3 concentrations were higher pre-STS (p=0.03) and post-STS in M2 when compared to M3 (p=0.04). GH did not change during the competition. Anaerobic power values were higher in M2 compared to the other moments (p=0.007). Peak velocity in the 30m velocity test also reached its highest value in M2, being significantly higher than in M1 (p=0.03).

Conclusions: IGF-I as well as IGFBP-3 showed variations during the competition, suggesting they were sensitive to both acute and chronic stimuli effects caused by the competition. Regarding motor performance, it should be stated that in predominantly anaerobic tests there was a tendency for the best results, with higher IGF-I and IGFBP-3 concentrations.