Relación entre la velocidad lineal y desempeño en el Illinois Agility Test según la posición de juego en futbolistas juveniles

Abstract

The aim of this study was to analyze the relationship between linear speed and performance in the Illinois Agility Test according to playing position in youth soccer players, as well as to determine the contribution of age to both physical performance variables. A quantitative, non-experimental, cross-sectional study with descriptive, comparative, and correlational scope was conducted in a sample of 50 youth soccer players aged 14 to 16 years. Two attempts of the 20-m sprint and the Illinois Agility Test were recorded, and the best result in each test was used for analysis. Statistical procedures included descriptive analysis, intrasession reliability assessment through ICC, CV, and SEM, one-way ANOVA with Tukey post hoc tests, Pearson and Spearman correlations, and age-adjusted linear regression models. The results showed significant differences among playing positions for both the 20-m sprint (F(2,47) = 15.30, p < 0.001, η² = 0.394) and the Illinois Agility Test (F(2,47) = 15.93, p < 0.001, η² = 0.404), with forwards showing the best performance, followed by midfielders and defenders. Intrasession reliability was very high for both tests (ICC = 0.9995 for sprint; ICC = 0.9999 for Illinois). In addition, an almost perfect positive relationship was found between both variables in the overall sample (r = 0.997, p < 0.001), and this pattern remained consistent across the three playing positions. However, after adjusting for age, playing position was no longer an independent predictor, whereas age remained significantly associated with performance in both tests. It can be concluded that linear speed and performance in the Illinois Agility Test are strongly associated in youth soccer players and that, although apparent differences by playing position exist, an important proportion of such differences seems to be explained by age. These findings highlight the need to interpret physical performance in youth categories by considering not only tactical role but also the athlete’s developmental stage.