Evaluation of the Illinois Change of Direction Test in Youth Elite Soccer Players of Different Age.

Change of direction ability is an essential pre-requisite in team sports athletes. The Illinois change of direction test has been routinely used for testing change of direction ability in soccer players. The aim of the present study was to evaluate the Illinois change of direction test in young elite soccer players in terms of its reliability, usefulness and relationship with body size. A total of one hundred and ninety-four male, national-level soccer players were recruited. They were classified into four age groups (U-8, U-10, U-12 and U-14). Participants were tested using the Illinois change of direction test twice, and basic indices of body size were obtained. The Illinois change of direction scores showed high relative and absolute reliability in all age groups (all intraclass correlation coefficients were >0.91, and the standard error of measurement was <5%). The usefulness analysis showed that the Illinois change of direction test could detect small changes in performance in the U-10 and U-12 groups. However, it could only detect moderate changes in performance in the U-8 and U-14 groups. Although the Illinois change of direction test detected significant performance differences among groups, scores were not significantly related to body size (-0.30<r<0.15; p > 0.05). Taking into account the test's high reliability and the appropriate level of usefulness, these results might support the use of the Illinois change of direction test as a standard measure for quantifying change of direction ability in young soccer players.