Bolckmans Sofie, Starkes Janet L, Towlson Chris, Barnes Chris, Parkin Guy, Helsen Werner F
Department of Movement Sciences, KU Leuven, Leuven, Belgium.
Institute of Exercise Training and Sport Informatics, German Sport University Cologne, Köln, Germany.
Front Sports Act Living. 2022 Mar 3;4:847438. doi: 10.3389/fspor.2022.847438. eCollection 2022.
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.
相对年龄选择偏差在全球所有主要足球联赛和青少年足球学院中都持续存在，相对年龄效应（RAE）通常表现为对相对年龄较大球员（有时也被证明是早熟球员）的过度选拔。本研究的目的是检验一种新的分配方法是否（i）消除了相对年龄效应，以及（ii）减少了同一选拔类别中球员之间可能存在的与成熟度相关的人体测量和体能特征方面的任何其他差异。在第一阶段，从23家英国职业足球俱乐部抽取了1003名学院足球运动员（9 - 16岁），观察到整个样本按出生季度（Q）存在明显的相对年龄效应（第一季度 = 45.0%，第四季度 = 9.8%），不同年龄组也是如此。使用新建议的重新分配方法，青少年球员按分配日期进行划分，分配日期定义为实足年龄与估计发育出生日期的中点。身高被用作生长曲线P50上的人体测量参考点，以确定这种新方法的发育出生日期。使用估计发育出生日期对球员进行重新分配后，球员分布更加均匀（第一季度 = 25.3%，第二季度 = 25.6%，第三季度 = 22.4%，第四季度 = 26.7%）。重新分配后，平均身高差减少了16.6厘米（从40.3 ± 7.08厘米降至23.7 ± 4.09厘米，d = 2.87）。分配后平均体重差减少了6.7千克（从33.2 ± 6.39千克降至26.5 ± 4.85千克，d = 1.18）。平均年龄差从1.8岁增加到3.9岁。与当前分组相比，共有42.7%的样本会被重新分配到不同年龄组。重新分配后，45%的人体测量和体能比较显示组内变异以变异系数（CV%）百分比表示有所降低。10岁以下球员的人体测量特征CV%降低幅度最大（-7.6%）。10岁以下球员组在各种体能特征方面的CV%降低幅度也最大（-7.5%）。通过消除相对年龄效应以及减少与成熟度相关的临时人体测量和体能差异，世界各地的足球学院可以使俱乐部和国家青年队的人才库多样化并扩大规模。总之，本研究提供了进一步证据，表明新提出的分配方法有潜力消除相对年龄效应，并通过减少人体测量和体能特征的组内变异创造一个更“公平的竞争环境”，为相对年轻、最终是晚熟的球员提供公平发展其天赋的机会。
