Resumen:
Talent identification (TI) in sport, which is the selection of individuals disposed to achieve elite
performance in adulthood, is often based on physical fitness testing. TI is linked to the phenomenon
called the Relative Age Effect (RAE), referring to the influence of birthdate on sports performance.
This retrospective study is based on the assumption that elite adult athletes possessed indicators
predictive of a successful career already at a young age. The study aimed to assess the differences
among Czech male tennis players according to 1) their tennis performance in adulthood, 2) their
birthdate in each semester (S). The participants were players U12 who were later among top 1000 in
the ATP Singles Rankings (SR). The research data was obtained during regular testing of the Czech
Tennis Association (1998–2019). Significant differences between subgroups R1 (SR 1st - 500th) and
R2 (SR 501st - 1000th) were found, surprisingly in favor of R2 in 4 variables. Significant differences
were found in favor of B1 (born in S1) in 2 variables, and in favor of B2 (born in S2) in 2 variables.
