Age-Group Differences in Skeletal Age, Anabolic Hormones, and Physical Fitness in Elite Youth Football Players from Under-13 to Under-16

ObjectivesFootball players between the ages of 13 and 16 were the subjects of this study to (i) compare skeletal age, growth hormone (GH), insulin-like growth factor-1 (IGF-1), VO2max, countermovement jump (CMJ) performance, and playing time across four consecutive age groups (under-13 to under-16), and (ii) investigate correlations between these metrics within each age group. Designcross-sectional research study. MethodsThe U13, U14, U15, and U16 groups included 122 elite male youth football players (14.13 {+/-} 1.14 years; 169.39 {+/-} 9.82 cm; 55.56 {+/-} 10.10 kg). The Fels method was used to determine skeletal age. Anthropometric measures included height, weight, and sitting height. The CMJ and Yo-Yo (VO2max) tests were used to assess physical fitness. GH and IGF-1 were measured in blood samples. Pearson correlation and one-way ANOVA were used. ResultsAnthropometric assessment, skeletal age, VO2max, CMJ, IGF-1, football training, and minutes playing all showed significant group differences, with the U16 group demonstrating the highest values and the U13 group the lowest (p < 0.001). There were no significant differences in GH (p = 0.172). Although there were no consistent relationships between GH or IGF-1 and height or weight, these variables did correlate with other factors; however, these associations varied by group. ConclusionsAcross the under-13 to under-16 span, skeletal age, physical fitness, and IGF-1 increased progressively between age groups, whereas GH did not differ. The impact of biological maturation on performance was demonstrated by the fact that older, more experienced players performed better than younger ones. The absence of a between-group difference in GH, despite progressive changes in the other measures, points to maturity-driven adaptations rather than a uniform hormonal response.