Abstract
Relative age selection bias persists within all major soccer leagues and youth soccer academies across the globe, with the relative age effect (RAE) being typically characterized as the over selection of relatively older players (who have sometimes also been shown to be early maturing). The aim of this study was to examine if a new allocation method (i) eliminates the RAE, and (ii) reduces the presence of any additional maturity-related differences in anthropometric and physical fitness characteristics which may exist between players within the same selection category. In the first phase, 1,003 academy soccer players [under (U) 9–16] from 23 UK professional soccer clubs were sampled and a clear RAE per birth quarter (Q) was observed for the overall sample (Q1 = 45.0% vs. Q4 = 9.8%) as well as for the different age categories. Using the newly suggested reallocation method, youth players were divided by allocation date which was defined as the midway point between the chronological age and the estimated developmental (ED) birthdate. Stature was used as an anthropometric reference point on the P50 of the growth curve to determine the developmental birthdate for this new method. After the reallocation of the players using ED, the distribution of players was more equally spread (Q1 = 25.3%, Q2 = 25.6%, Q3 = 22.4%, Q4 = 26.7%). After reallocation, the mean delta stature was reduced by 16.6 cm (from 40.3 ± 7.08 to 23.7 ± 4.09 cm, d = 2.87). The mean delta body mass difference after allocation was reduced by 6.7kg (from 33.2 ± 6.39 to 26.5 ± 4.85 kg, d = 1.18). The mean age difference increased from 1.8 to 3.9 years. A total of 42.7% of the sample would have been reallocated to a different age group compared to the current one. After reallocation, 45% of the anthropometric and physical fitness comparisons showed reductions in the within-group variation expressed as a percentage of coefficient of variation (CV%). The U10 players demonstrated the largest reduction in CV% (−7.6%) of the anthropometric characteristics. The U10 squad also showed the largest reduction in CV% for various physical fitness characteristics (−7.5%). By both eliminating the RAE and reducing temporary maturity-related anthropometric and physical fitness differences, soccer academies across the world may diversify and increase the size of the talent pool both for clubs and national youth teams. In conclusion, this study provides further evidence that the newly proposed allocation method shows the potential to remove the RAE and to create a more “leveled playing field” by reducing the within-group variation of anthropometric and physical fitness characteristics affording relatively younger, and eventually, late-maturing players the opportunity to develop their talent fairly.
Highlights
Academy soccer players’ [e.g., under (U)9 to U23] development and talent identification are multifaceted and complex (Larkin and O’Connor, 2017; Towlson et al, 2019, 2021a; Doncaster et al, 2020; Romann, 2020)
Players that were born in Q1 had the highest representation (45%), followed by players born in Q2 (25.4%), Q3 (19.5%), and Q4 (9.8%)
An uneven distribution was identified for each annual group, with 37.5– 52.2 % of players born in Q1 and 6.3–13.3% in Q4 (Figure 1)
Summary
Academy soccer players’ [e.g., under (U) to U23] development and talent identification are multifaceted and complex (Larkin and O’Connor, 2017; Towlson et al, 2019, 2021a; Doncaster et al, 2020; Romann, 2020). Relative age (i.e., players birthdate in relation to the cut-off dates for the domestic soccer season; Helsen et al, 1998, 2000, 2005), and maturity-related selection bias (Lovell et al, 2015; Towlson et al, 2017) onset by the highly individualized timing of the adolescent growth spurt (Philippaerts et al, 2006) [typically reported as estimated (Fransen et al, 2021) peak height velocity (PHV) (Mirwald et al, 2002; Moore et al, 2015; Fransen et al, 2018; Kozieł and Malina, 2018) or percentage of final adult stature (Khamis and Roche, 1994; Towlson et al, 2021c)] have been offered as separate (Helsen et al, 2005) and collective (Cobley et al, 2009; Lovell et al, 2015) causal factors for the overrepresentation of players who are either relatively older and/or early maturing Both methods are commonly utilized by professional soccer academies (Salter et al, 2021). There is a need for new and innovative methods which can tackle both, despite their individualized timing of effect
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