Evidence for the Relative Age Effect in the Spanish Professional Soccer League

Abstract

The concept of the relative age effect refers to the consequences of the physical and psychological differences that may exist between those born earlier or later within the same calendar year. The objective of the present study was to examine this phenomenon in Spanish professional soccer, identifying the influences of the competitive level and the club of origin. The sample comprised 2,130 individuals from five competitive categories: under 12 (U12; n = 480), under 14 (U14; n = 338), under 16 (U16; n = 390), under 19 years old (U19; n = 489) and professional players (n = 433), with nine teams from the Spanish professional soccer league (PSL). Statistical analysis was based on a chi-squared test followed by calculation of the odds ratios and 95% confidence intervals. The main results show that at all levels of competition there was over-representation of individuals born in the first few months of the year. By clubs, the same over-representation was observed. It may be concluded that the relative age effect is consistent and exists throughout Spanish soccer, whether at youth or professional levels. An analysis by age categories showed a more pronounced effect in those competitions in which the youngest players participate, while in clubs the effect continued to be significantly present in all cases investigated in the study.

Relative Age-Related Biases in Objective and Subjective Assessments of Performance in Talented Youth Soccer Players

“…Votteler and Höner (2017) found that, depending on age group, 66-69% of the youth academy players in Germany, and even 72-81% of the German youth national players, are born in the first half of the year. While the RAE is still present in adult professional soccer leagues, its extent is considerably smaller than in youth soccer (e.g., Doyle and Bottomley, 2018;Yagüe et al, 2020).…”

“…RAEs occur not due to a single factor but rather due to a complex interaction of individual constraints (e.g., an individual's date of birth, maturation, and abilities), environmental constraints (e.g., talent promotion programs and coaches), and task constraints (e.g., the physical and physiological demands of the sport). This interaction leads to advantages for early-born players in athletically demanding sports such as track and field (Romann and Cobley, 2015), ice hockey (Nolan and Howell, 2010), handball (Wrang et al, 2018), basketball (López de Subijana and Lorenzo, 2018;Kalén et al, 2021), and soccer (Votteler and Höner, 2017;Hill et al, 2020a;Romann et al, 2020;Yagüe et al, 2020). This is particularly the case in team sports, where the specific demands of different playing positions can even be associated with different RAEs (Wattie et al, 2015).…”

Low prevalence of relative age effects in Luxembourg’s male and female youth football

“…As a result, the age difference within one birth cohort can go up to one year, known as the relative age. In football, the relative age difference can increase to 24 or 36 months when age groups are defined in two or three-year bands [ 2 ]. Especially during puberty, inter-individual differences in the onset and speed of maturational growth, and consequently physiological performance [ 3 ], can vary significantly between members within one age category [ 4 ].…”

“…The popularity of football especially in many European countries results in a large pool of players that favour performance-focussed selection procedures (environmental constraint) and in turn increase the prevalence of the RAE [ 4 ]. However, while this interaction of constraints applies to many established football nations such as Germany or Spain [ 2 , 19 ], research in smaller countries is limited. These nations are often forced to apply a more open system including flexible selection processes (‘open-door’ policy) due to the limited number of players.…”

Relative age effect on student-athletes of Mato Grosso state (Brazil) participating in the National School Games depending on sex, age category, and sport type

“…In sports, athletes' training categories are grouped in accordance with their year of birth, in order to provide equality in maturity in competitions [4]. However, studies have shown that some athletes are predisposed to obtain higher anthropometric, physical, and cognitive development, as well as psychological factors than relatively younger ones, even at the same chronological age or within the same age category [5,6].…”