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This study investigated whether ACTN3 R577X, AMPD1 C34T, I/D ACE, and M235T AGT polymorphisms can affect performance tests such as jumping, sprinting, and endurance in 220 young male athletes from professional minor league soccer team from São Paulo Futebol Clube, Brazil. I/D ACE and M235T AGT polymorphisms were also analyzed according to cardiac and hemodynamic parameters. Athletes were grouped or not by age. DNA from saliva and Taqman assays were used for genotyping 220 athletes and the results were associated with performance tests. Ventricle mass, ventricle end-diastolic diameter, end-diastolic volume, and ejection fraction were assessed by echocardiogram. Arterial pressure, heart rate, and oximetry were assessed by a cardioscope. The main results of this study were that athletes who carried RR/RX (ACTN3) and DD (ACE) genotypes presented better performance during jump and sprint tests. On the other hand, athletes with ID/II genotype presented better results during endurance test, while AGT genotypes did not seem to favor the athletes during the evaluated physical tests. CC genotype (AMPD1) only favored the athletes during 10-m sprint test. Although there are environmental interactions influencing performance, the present results suggest that RR/RX ACTN3 and ACE DD genotypes may benefit athletes in activities that require strength and speed, while II ACE genotype may benefit athletes in endurance activities. This information could help coaches to plan the training session to improve the athletes' performance.

The aim of this study was to examine the influence of hormonal status, anthropometric profile, sexual maturity level, and physical performance on the technical abilities of 40 young male soccer players during small-sided games (SSGs). Anthropometric profiling, saliva sampling, sexual maturity assessment (Tanner scale), and physical performance tests (Yo-Yo and vertical jumps) were conducted two weeks prior to the SSGs. Salivary testosterone was determined by the enzyme-linked immunosorbent assay method. Technical performance was determined by the frequency of actions during SSGs. Principal component analyses identified four technical actions of importance: total number of passes, effectiveness, goal attempts, and total tackles. A multivariate canonical correlation analysis was then employed to verify the prediction of a multiple dependent variables set (composed of four technical actions) from an independent set of variables, composed of testosterone concentration, stage of pubic hair and genitalia development, vertical jumps and Yo-Yo performance. A moderate-to-large relationship between the technical performance set and the independent set was observed. The canonical correlation was 0.75 with a canonical R2 of 0.45. The highest structure coefficient in the technical performance set was observed for tackles (0.77), while testosterone presented the highest structure coefficient (0.75) for the variables of the independent set. The current data suggest that the selected independent set of variables might be useful in predicting SSG performance in young soccer players. Coaches should be aware that physical development plays a key role in technical performance to avoid decision-making mistakes during the selection of young players.

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-The aim of this study was to compare the birth-date distribution of youth athletes of a high-level Brazilian soccer club with the general population of the same age group. In a cross-sectional study, the birth date of 341 youth athletes (under 10-20) was compared with a reference population (live births that occurred in São Paulo state in the same age group; n = 5,480,868). The subjects were divided into quarters of birth: 1 st = January-March; 2 nd = April-June; 3 rd = July-September; 4 th = October-December. The chisquare test (χ 2 ) was used to compare the expected (reference population) and observed (athletes) distributions. It was detected a significant difference between the expected distribution and observed distribution (χ 2 = 29.53; p<0.0001), with a higher percentage of athletes born in the 1 st quarter (47.5%) and a lower percentage in the 4 th quarter (8.8%). The present results confirm the occurrence of the relative age effect (RAE) during the player selection process in a top-level Brazilian soccer club. The occurrence of this phenomenon during the selection and development of young athletes needs to be taken into account and should be analyzed carefully in order to minimize the loss of potential youth soccer talent. Further studies are required to identify the determinants of RAE and to establish preventive strategies that ensure a more efficient selection process of young soccer players. Key words: Athlete; Maturation; Relative age effect; Soccer; Talent identification; Youth. Resumo -O objetivo do presente estudo foi comparar a distribuição das datas de nascimento dos atletas das categorias de base de um clube da elite do futebol brasileiro com a população do estado de São Paulo da mesma faixa etária. Por meio de estudo transversal, as datas de nascimento de 341 atletas das categorias de base de um clube de São Paulo (sub 10-20) foram comparadas com uma população de referência (nascidos vivos do Estado de São Paulo da mesma faixa etária; n = 5.480.868). Os indivíduos foram distribuídos 400The relative age effect in soccer Massa et al.