V.T. Costa ^{1, 2}, M.A. Simim ¹, F. Noce ², I.T. Costa ^1,2,3, D.M. Samulski ¹, L.C. Moraes ¹

The relative age of athletes has raised the attention of many researchers. The focus of these investigations understands the interference of this parameter in the identification of talents and the training of future elite athletes. Thus, the aim of this paper was to to evaluate and compare the existence of differences between semesters and birth date quartiles in professional soccer participating in the Brazilian Soccer Championship Series A (1^st division) and B (2^nd division) in 2008. Fourty clubs that participated in the Brazilian Soccer Championship Series A and B were evaluated, totalizing 1022 players (483 players in the 1^st division and 539 players in the 2^nd division). The players were grouped per birth date into year quartiles and semesters. The data showed that there was a preference of clubs from the two championship series for hiring athletes born in the 1^st semester. Further, differences were absent only between quartiles 2 and 3 and a clubs` preference for 1<sup>st</sup> quartile athletes was also observed. We can conclude that the relative age stands out as a variable in the elite soccer athlete selection and training, as the comparisons show the clubs` preference for athletes born early in the year.

Key words: soccer, age, elite, players

Among the several psychosocial variables, the relative age resulting from the categorization of athletes` birth date or birthday quartile has raised the attention of many researchers (Coté, Macdonald, Baker & Abernethy, 2006; Glamser & Vicent, 1999; Simmons & Paull, 2001; Vicent & Glamser, 2006). The focus of these investigations understands the interference of this parameter in the identification of talents and the training of future high performance elite athletes. Ferreira (1999) defines quartile as “any of the three quarter values that divide the frequency distribution area of a domain area into four equal parts of the total area”. The sport birth date quartile is defined as the subdivision of the birth year of athletes in months in four equal areas as categories (e.g. athletes with birth date in January, February, and March belong to the 1^st quartile).

In sports literature, it is common to find studies (Vaeyens, Philippaerts & Malina, 2005; Vicent & Glamser, 2006) on relative age referred to as the difference in age between people in the same age group involved in the practice of a certain sport. According to Folgado, Caixinha, Sampaio and Maças (2005), the first studies on relative age were made in the education area. Researchers sought to identify children with birth dates closer to the beginning of the year who performed better comparatively to children born closer to the end of the year. In sports, the relative age is an advantage factor in the selection of athletes, as individuals born closer to the beginning of the year tend to be either favored or disregarded, particularly because of physical aspects in relation to other athletes born closer to the end of the year (Musch & Grondin, 2001; Musch & Hay, 1999).

Musch and Grondin (2001) made an extensive revision of studies on relative age in different sports, including soccer.  In their meta-analysis of 11 specific studies on relative age in soccer in 11 countries, they identified a preference for athletes born in the first two quarters of the year. This finding is relevant in sports practice and investigation, since in general, all the investment clubs make in the identification, selection, and training of young talents in the soccer starter category aims to form of professional (elite) soccer athletes.

Therefore, this study aims to evaluate and compare the existence of differences between semesters and birth date quartiles in professional soccer participating in the Brazilian Soccer Championship Series A (1^st division) and B (2^nd division) in 2008.

Methods

Sample

It was evaluated all 40 clubs that participated in the Brazilian Soccer Championship Series A and B (2008), totaling 1,022 athletes (M= 25.34, SD= 4.51), with 483 players (M= 25.06, SD= 4.33) in the 1^st division and 539 athletes (M= 25.59, SD= 4.66) in the 2^nd division of Brazilian soccer.

The athletes were grouped per birth date into quartiles as follows: 1^st quartile (January, February, March), 2^nd quartile (April, May, June), 3^rd quartile (July, August, September), and 4^th quartile (October, November, December).

The semester grouping followed the same rationale: 1^st semester (from January to July) and 2^nd semester (from July to December).

Instruments

Statistical Treatment

Statistical analyses, means, standard deviation, frequency distribution, and inferential chi-square test were performed with the package SPSS 12.0.

Results

Table 1 presents the general data per semester and the birth date quartiles for Series A and B of the Brazilian Soccer Championship. It was observed the preference of clubs from the two championship series for hiring athletes born in the 1^st semester.

Table 2 locates the differences per for fro Brazilian soccer athletes. Notice that differences were absent only between quartiles 2 and 3. It can also be observed the Brazilian clubs` preference for 1^st quartile athletes to the others.

Table 1. Comparison of relative age of Brazilian soccer athletes

Table 1. Comparison of relative age of Brazilian soccer athletes (continuation)

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                                         *p< 0.01

Table 2. Quartile comparison within Series A and B championships

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*p< 0.05 **p< 0.01

Discussion

In relation to the semester of birth, our results confirm the results of Vaeyens et al. (2005), who also found a preference for 1^st semester-born athletes in a longitudinal study of Belgian soccer athletes. Musch and Hay (1999) compared the relative age plots for the general population of different countries (Brazil, Japan, Australia, and Germany) and for professional soccer players and identified a significant preference for 1^st semester-born players.

The analysis of the differences found in birth date quartile reveals that they are very close to the results in the international literature. Glamser and Vicent (1999) investigated birth date quartile in American athletes and concluded that athletes born in the beginning of the year who became professionals predominate. Musch and Hay (1999) also found the predominance of soccer players born in the 1^st and 2^nd quartiles in a study of professional athletes from different social-cultural contexts and countries when compared to the general population.

A decade later, the results found in the Brazilian professional soccer for year 2008 are similar to those reported by Musch and Hay (1999) in their analysis of Brazilian championship professionals (1995-1996) with the clubs` preference for athletes born in the 1^st and 2^nd quartiles over 50% of the sample and a low score of athletes born in the 4^th quartile.

References

Coté, J., Macdonald, D.J., Baker, J., & Abernethy, B. (2006). When “where” is more important than “where”: Birthplace and birthdate effects on the achievement of sporting expertise. Journal of Sports Science, 24(10), 1065-1073.

Ferreira, A.B.H. (1999). Aurélio século XXI: O dicionário da língua portuguesa (3ª ed.). Rio de Janeiro: Nova Fronteira.

Folgado, H.A., Caixinha, P.F., Sampaio, J., & Maças, V. (2005). Efeito da idade cronológica na distribuição dos futebolistas por escalões e pelas diferentes posições específicas. Revista Portuguesa de Ciência do Desporto, 6(3), 349-355.         [ Links ]

Glamser, F.D., & Vicent, J. (1999). The relative age effect among elite American youth soccer players. Journal of Sport Behavior, 17(1), 31-39.

Musch, J., & Grondin, S. (2001). Unequal competition as an impediment to personal development: A review of the relative age effect in sport. Developmental Review, 21, 147-167.

Musch, J., & Hay, R. (1999). The relative age effecting soccer: Cross-cultural evidence for a systematic discrimination against children born late in the competition year. Sociology of Sport Journal, 16, 54-64.

Simmons, C., & Paull, G.C. (2001). Season-of-birth bias in association football. Journal of Sports Science, 19, 677-86.

Vicent, J., & Glamser, F.D. (2006). Gender differences in the relative age effect among US olympic development program youth soccer players. Journal of Sports Science, 24(4), 405-413.

1 - Universidade Federal de Minas Gerais, LAPES-CENESP, Belo Horizonte, Brazil

2 - Centro Universitário de Belo Horizonte, LAPES, Belo Horizonte, Brazil

3 - Faculdade de Desporto da Universidade do Porto, FADEUP, Porto, Portugal