Reliability of ‘in-season’ fitness assessments in youth elite soccer players: a working model for practitioners and coaches.

Purpose: To assess the reliability of a battery of field tests when performed around habitual training during one micro-cycle of the ‘in-season’ period in youth elite soccer players. Methods: n=19 English Premier League academy players (mean ± SD: age, 18.3±0.2 years; stature, 1.80±0.05 m; body mass, 76.5±7.5 kg; VO2 max; 62.3±4.38 ml·kg-1·min-1 Sum of 8 skinfolds; 64.8±17.4 mm) performed; ‘1RM half-back squat (HBS)’, ‘vertical jump’ (VJ), ‘Yo-Yo IR2’, ’5, 10 & 20 m, sprint’, ‘the agility T-test’ and a ‘repeated sprint ability’ assessments around their habitual ‘in-season’ training and match-play on two occasions. Typical error (TE), coefficient of variation (CV), the smallest worthwhile change (SWC) was then calculated between trials. Test usefulness was then calculated by comparing the ‘SWC’ to the TE and rated as; good, OK or marginal. The smallest difference needed to be considered real (MD), was also calculated using the equation (TE×1.96×√2). Results: Most assessments demonstrated relatively high levels of reproducibility (CV; 0.3 - 4.3 %) to witness an “almost certain beneficial change” (i.e.,>MD) changes of approximately 5% (RSAbest, RSAmean, 10m & 20m sprint, ‘agility T test’ and 1RM HBS), and 11.5% (VJ, 5m sprint, and Yo-Yo IR2) are needed. Conclusions: The present training and testing ‘model’ is reliable and could be used when evaluating the fitness of highly trained youth elite soccer players during the ‘in-season’ period.