Relative age effect and its relationship with morphological characteristics and performance in young soccer players

In soccer, the relative age effect (RAE) was observed in both adult and young players. The RAE appears to be more pronounced in elite sports, probably by the need to select the best players to compete internationally. This study review: (1) the prevalence of RAE in soccer players, (a) considering competitive level (b) and specific position and (2) association between RAE (a) and anthropometric characteristics, (b) physical fitness components and technical skills. A total of 12 studies met all inclusion criteria for this review. One trial (meta-analysis) was included after the eligibility process. Overall, 77675 young soccer players were analysed. In all studies, significance level of 0.05 was set for the type I error. There is a consensus about the presence of an RAE in men's soccer, and the percentage of players born in the first quarter in the selection year for professionals is high, with peak values found for elite young athletes, and a large decrease is evident throughout the regional and school representation. The relationship between RAE and the specific position is controversial, according to few studies. It is likely that players born in the first quarter differ in a variety of anthropometric characteristics and physical fitness components compared with peers born in the last quarter. Researchers need to understand the mechanisms by which RAE increase and decrease in order, to reduce and eliminate this social inequality that influence the experiences of athletes, especially in periods of development. Organizational and practical intervention is required.Original Abstract: No futebol, o 'efeito da idade relativa' foi encontrado tanto em jogadores adultos quanto em jovens. O 'efeito da idade relativa' parece ser mais pronunciado em esportes de elite, provavelmente, pela necessidade de selecionar os melhores jogadores para competir em nivel internacional. Revisamos: (1) a prevalencia do 'efeito da idade relativa' em jogadores de futebol, (a) considerando o nivel competitivo (b) e a posicao especifica e (2) a associacao entre o 'efeito da idade relativa' (a) sobre as caracteristicas antropometricas, (b) componentes da aptidao fisica e habilidades tecnicas. Um total de doze estudos preencheram todos os criterios de inclusao para esta revisao. Um ensaio (meta analise) foi incluido apos o processo de elegibilidade. O total de 77675 jovens futebolistas foi analisado. Em todos os estudos, um nivel de significancia de 0.05 foi estabelecido para o erro tipo