Relative age effect at Czech elite swimmers in U12 category

Abstract

The Relative Age Effect (RAE) is phenomenon that strongly influences youth sport development.The RAE refers to a disproportionately high percentage of athletes born early in the calendar selection year. Number of studies, especially in team sports, has proved this fact. However, there is still a lack of studies in individual sports, such as swimming, which makes it impossible to have a sufficient understanding of the RAE problem in a given sport. The aim of our study was to verify RAE in young elite swimmers (n = 202) who participated in Czech Republic U12 Championships (1) in male and female samples (2) according to swimming disciplines and distances (3) and performance (times in individual disciplines) between individual quartiles /semesters of birth. The analysis was performed with the use of adequate statistical (chi -square test, Mann-Whitney U test) and effect size (effect size index w and effect size index r ) tests. The analysis showed a significant RAE only in the whole sample (p = 0.015, w = 0.228, ES = medium), in sex distribution RAE was not present. A significant RAE, in the division according to swimming disciplines and swimming distances, was found in males in the breaststroke /100 m/ (p = 0.001, w = 0.763, ES = large), breaststroke /200 m/ (χ 2 (3) = 13.196, p = 0.004, w = 0.663, ES = large) and in the individual medley /200 m/ (χ 2 (3) = 12.214, p = 0.007, w = 0.638, ES = large). In females, there was a significant RAE in freestyle /50m/ (p < 0.001, w = 0.774, ES = large) and freestyle /100m/ (p = 0.001, w = 0.751, ES = large). Analysis of performance differences between research categories (Si ) in the form of time in disciplines, showed a statistically significant difference between the dependent variables (sex, distance, discipline) by different independent variables (Si ) only in case of female sample: freestyle /100m/ (p = 0.011), individual medley /100m/ (p = 0.028), butterfly /200m/ (p = 0.015) and individual medley /400m/ (p = 0.002).