The reliability of a modified 505 test and the change-of-direction deficit in elite young football players.

Introduction: In line with the ‘Elite Player Performance Plan’ (EPPP) governed by the English premier league, the use of a modified 505 test (M505) (using a 1-m lead-in to the 10-m shuttle component) is compulsory as part of national benchmark fitness testing in leading academies. However, the reliability of this test has not been determined in elite youth football players. Furthermore, the change-of-direction deficit (derived from 505 test time) is proposed to be a better way of isolating COD ability, yet this measure is not used frequently in football. Therefore, this study aimed to assess M505 and COD deficit reliability in elite youth players.
Methods: A total of 110 players from the Under [u] 12-18 years age groups were recruited (u18 n = 26, u16 n=26, u14 n=39, u12 n=19) from two English Premier League Category 1 Academies. To assess the reliability of the M505 and COD deficit, players completed the M505 twice (two trials on each side) in 7-days with best time recorded for analysis. To calculate COD deficit, best 10-m sprint time recorded during the testing window was subtracted from the M505 time. Players were familiar with the tests, and all were preceded by a standardised warm-up and completed indoors on artificial field turf. Performance times are displayed as mean ± standard deviation. Mean change (%), typical error (CV, %), and intraclass correlation coefficients (ICC) were calculated, with age-group specific thresholds used to quantify the magnitude of mean change and typical error. Standardised thresholds were used to quantify the magnitude of ICC’s.
Results: Performance times for the M505 were 2.42 ± 0.08 s, 2.46 ± 0.09 s, 2.59 ± 0.10 s, 2.70 ± 0.12 s for the u18, u16, u14, and u12 groups, respectively. For COD deficit, performance times were 0.70 ± 0.09 s, 0.72 ± 0.09 s, 0.79 ± 0.10 s, 0.82 ± 0.10 s for the u18, u16, u14, and u12 groups, respectively. For the M505, Mean changes (%) were small to moderate (-0.8 to -3.2%) for M505-Left and trivial to small (-2.1 to 0.9%) for M505-Right in all age groups. Typical errors in M505 were moderate to large in all age groups (2.0 to 3.5%), while Intraclass correlation coefficients (ICC) were low to moderate (0.29 to 0.70). For COD deficit, small to moderate changes were observed in COD deficit-Left (-2.4 to -11.3%) in all age-groups, and COD deficit-Right (-7.3 to 3.2%) in the u14, u16, and u18 groups, mean changes in COD-Right were trivial in the u12 group. Typical errors in COD deficit were moderate to large (7.1 to 12.0%), while ICC’s were very low to moderate (0.19 to 0.72) in all age groups.
Conclusions: The M505 should be used with consideration of the high typical errors in elite youth players. While COD deficit has been highlighted as a better way of assessing change-of-direction ability, this measure does not appear suitable for use in this population.