The relative age effect in young athletes: A countywide analysis of 9–14-year-old participants in all competitive sports

Abstract

The relative age effect (RAE) has primarily been investigated in male athletes involved in popular sports and high-level competitions. However, occurrence of RAE in other types of sports at the grassroots level, particularly in female athletes, is less well-studied. Thus, we examined the RAE in a large cohort of young athletes who participated in all competitive sports in Bizkaia, Spain, according to gender and specificity of the sport. The birth dates of 38,381 participants (65.1% males and 34.9% females) aged 9–14 years old in 37 competitive sports were analyzed. Birth dates were divided into four birth-quarters and compared to those of all children born in the same period using a χ2 goodness-of-fit test and standardized residuals. The effect size Cramer’s V was measured, and odds ratio and 95% confidence intervals were calculated to determine the odds of athletes born in January playing in the highest leagues. In the total sample, in boys RAE was evident in football, but only in higher-competition leagues (p<0.001, large effect size). In girls, RAE was evident in the most popular team sports: basketball (p<0.001, large effect size in basketball 1st league), handball and football (p<0.05, both small effect sizes). Players born in January were 3.23- and 2.89-times more likely to play in the 1st leagues than those born in December, for boys (football) and girls (basketball) respectively. In the overall analysis and in the remaining sports, presence of RAE was negligible. Therefore, the date of birth does not seem to be a constraint to participating in most sports in Bizkaia. The potential mechanisms for RAE are multifactorial and complex, yet a combination of factors, such as the popularity of a sport and the depth of competition, physicality and social influences may be involved. We discuss these mechanisms and potential measures to mitigate RAE.

Relative age in Brazilian swimmers and para swimmers

“…The meaningful swimmer's representation, who were born in the 2nd quartile and the less amount of para swimmers who were born in the 3nd and 4nd quartiles of the year seem to evidence a discrimination against relatively younger children solely because they were born in certain months of the year 11,16,17 and corroborate with previous studies 6,9,18 . In fact, swimming is a sport in which the greatest prevalence of the relative age effects has been observed, with increased participation in championships for those born in the first quartiles 9,10 and a high perceived precocity in elite competition 1 .…”

Relative age effect in elite Brazilian athletes in different combat sports: an observational study

“…However, they found an RAE reverse for the female U-11 karate category. We emphasize that, unlike the present study, Gil et al [ 6 ] analyzed karate only in a general way without considering the division by modalities (kumite and kata), in addition to considering all the athletes in the ranking, while the present study used only the top 20 in each category and weighted the analyses by body weight categories. The difference in the characteristics of each study may explain the different responses, demonstrating that the investigation, depending on how it is carried out, may or may not have RAE.…”

“…In a study that sought to analyze the RAE in categories from U-9–U-14 in athletes from multiple sports, Gil et al [ 6 ] did not find the presence of RAE in any male karate category. However, they found an RAE reverse for the female U-11 karate category.…”

“…RAE has been previously analyzed in several sports, including combat sports such as karate, judo and taekwondo [ 6 ]. In combat sports where wrestling takes place, categories are divided by sex, year of birth and subcategories by body weight [ 7 ].…”

Relative age effects in track-and-field: Identification and performance rebalancing

“…For example, the 1500 m race is not popular under the age of 15, making the detection process difficult. As suggested (Delorme et al, 2011) and as shown in a study of young Spanish sportsmen between 9 and 14 years old (Gil et al, 2021), there may be a sport popularity effect that is at the origin of the relative age effect. Indeed, the larger the number of participants, the stronger the RAE, which has been shown at the level of different sports (football, rugby, ice hockey) but we can also imagine that this is the case within a single sport for several events.…”