Resumen:
The aim of this study was to determine whether there is any Relative Age Effect (RAE) in Czech male and female junior tennis players in the U16 age category. The participants were 6906 male and 4171 female players who were included in the official rankings of the Czech Tennis Association in 2003–2017. The athletes were divided into three performance subgroups (“ranked”, “top 100”, “top 10”). The research data were analyzed by the statistics methods: relative and absolute frequency, the ChiSquare Goodness of Fit test , and the Chi-Square Test of Independence with the use of effect size (ES index w). Only a small influence of the RAE was found among male and female junior players in all three performance subgroups in the whole period 2003–2017. A significant RAE (ES trivial and small) was observed among male players in “ranked” and “top 100” subgroups; in the “top 10” subgroup, there was no significant RAE (ES small). Among female players in “ranked” and “top 100” subgroups, a significant RAE (ES trivial and small) was observed; no significant RAE (ES small) was found in the “top 10” subgroup. The biggest number of athletes born in the first semester (S1) was identified among male players in “top 100” (66%), among female players in “top 10” (59%); in the other two subgroups, their number was over one half in both sexes. The sex difference between male and female players was in case of the “top 100” subgroup significant (ES small) in favor of male players; in the other two subgroups, the sex-differences were not significant (ES trivial). Findings of this study show that a higher number of tennis players is born in the first semester of the year, however, only a small influence of the birthdate on performance differences between athletes was proven.
