Birth month distribution and anthropometric measures of U-15 national elite soccer players

Abstract The aim of this study was to analyze the birth month distribution and anthropometric measurements of U-15 elite soccer players. The sample consisted of 400 athletes (15.4 ± 0.4 years, 171.0 ± 10.6 cm and 63.0 ± 8.8 kg) participants of the 11th edition of the Brazil U-15 Soccer Cup, who had their birth month information and height and body mass measures obtained from data available on the organization’s website. Athletes were separated according to the categorization of chronological age into four-month periods: 1st quarter (1st QDT), athletes born between January and April; 2nd quarter (2nd QDT), those born between May and August, and 3rd quarter (3rd QDT), those born between September and December. The non-parametric chi-square test (X2) was used to analyze the possible differences between observed and expected birth date distributions in the four-month periods. The significance level was P<0.05. The results show that the number of players born in 1st QDT was higher when compared to 2nd QDT and 3rd QDT (P<0.05), and higher when compared to 2nd QDT with 3rd QDT (P<0.05). For variables height and body mass, it was observed that players born in 1st QDT presented values significantly higher than those born in 2nd QDT and 3rd QDT (P<0.05). In the same way, players born in 2nd QDT presented higher values than those born in 3rd QDT (P<0.05). It could be concluded that the relative age effect exerts an influence on the selection of Brazilian U-15 soccer players because it is associated with differences in the anthropometric characteristics of these young players.

摘要 本研究旨在分析15岁以下（U-15）精英足球运动员的出生月份分布与人体测量学指标（anthropometric measurements）。研究样本为参与第11届巴西U-15足球杯赛的400名运动员，其年龄为15.4±0.4岁，身高171.0±10.6cm，体质量63.0±8.8kg，相关出生月份信息及身高、体质量数据均取自赛事组委会官网公开资料。研究按照实足年龄的出生月份将运动员划分为四个季度区间：第一季度（1st QDT）为1-4月出生的运动员，第二季度（2nd QDT）为5-8月出生者，第三季度（3rd QDT）为9-12月出生者。本研究采用非参数卡方检验（chi-square test，χ²）分析四个季度区间内实际出生分布与期望出生分布的潜在差异，检验显著性水平设定为P<0.05。结果显示，第一季度出生的运动员人数显著高于第二季度与第三季度（P<0.05），且第二季度出生人数亦显著高于第三季度（P<0.05）；在身高与体质量指标方面，第一季度出生运动员的测量值显著高于第二、第三季度出生者（P<0.05），同理，第二季度出生运动员的指标值亦显著高于第三季度（P<0.05）。综上可得出结论：相对年龄效应（relative age effect）会对巴西U-15足球运动员的选拔产生影响，因其与这些年轻运动员的人体测量学特征差异存在关联。