Squid male alternative reproductive tactics are determined by birth date.

Alternative reproductive tactics (ARTs) are discontinuous phenotypes associated with reproduction, observed in males of many species. Typically, large males adopt a tactic of competing with rivals for mating, while small males adopt a tactic of stealing fertilization opportunities from the large males. The 'birth date hypothesis', proposing that the date of birth influences the determination of each male's reproductive tactic, has been tested only in teleost fish to date. Here, the birth date hypothesis was tested in ARTs of Japanese spear squid Heterololigo bleekeri (consort/sneaker) by analysing statolith growth increments. The birth date significantly differed between consorts (early-hatched) and sneakers (late-hatched). However, no differences were detected in growth history up to 100 days from hatching. Most immature males caught during the reproductive season were larger than sneakers, and their hatch date was similar to that of consorts, suggesting that these immature males had already been following a life-history pathway as a consort. These results indicate that ARTs of H. bleekeri are determined based on their hatch date in early life. This study firstly suggests that the birth date hypothesis applies to aquatic invertebrates, suggesting that the mechanism by which birth date determines the individual phenotype is a phenomenon more common than previously believed.

The Relative Age Effect on YoungAthletes of Para-Athletics: Birth quartile analysis and performance in individual athletic events / El Efecto de la Edad Relativa en los Atletas Jóvenes de Paratlético: Análisis de cuartil denacimiento y desempeño en eventos atléticos individuales / O Efeito da Idade Relativa em Jovens Atletas de Paraatletismo: Análise do quartil de nascimento e do desempenho em eventos individuais de atletismo

El Efecto de la Edad Relativa (EER) es un fenómeno caracterizado por una sobrerrepresentación significativa de atletas nacidos en los primeros meses del año competitivo en la misma categoría deedad que se ha observado en categorías juveniles de atletismo. Sin embargo, hay una falta de investigación para investigar este fenómeno y su relación con el deporte para, y no está claro si este efectoestá presente en los jóvenes atletas. Por lo tanto, nuestro estudio examinó la existencia de EER en jóvenes atletaspara-atléticos (categorías U16, U18 y U20) y el rendimiento en eventos deportivos individuales según el cuartil denacimiento (Q1, Q2, Q3 yQ4). Las fechas de nacimiento se recogieron de 700 jóvenes atletas masculinos de deportes para que participaran en eventos deportivos individuales entre 2018 y 2019 en las categorías U16, U18 y U20. En resumen, se observó una distribución desigual de las fechas de nacimiento por cuartil cuando un mayor número de jóvenes para-atletas nació en el primer trimestre del año para U16 (χ²3= 18.785; p = .0003; Phi efecto = 0.45), U18 (χ²3= 6.846; p= .05; Phi efecto = 0.17), y U20 (χ²3= 10.156; p = .017; Phiefecto = 0.17). Sin embargo, cuando comparamos el desempeño de los atletas por evento (eventos de atletismo) y por separado por cuartil, no se encontró diferencia significativa (p> .05). En conclusión, nuestro estudio evidenció el papel influyente de laedad relativa en atletismo, pero parece que este fenómeno no está relacionado con el rendimiento en atletismo.(AU)

The Relative Age Effect (RAE) is a phenomenon characterized by a significant over-representation ofathletes born in the first months of the competitive year in the same age category that has been observed in athletics juvenile categories. However, there is a lack of research to investigate this phenomenon and its relationship with para-sport, and it isnot clear whether this effect is present in young para-athletes. Thus, the present study aims to examine the existence of RAE in young para-athletics athletes (U16, U18, and U20 categories) and the performance in individual athletic events according to the birth quartile (Q1, Q2, Q3, and Q4). Birth dates were collected from 700 young male athletes from para-sport who participated in individual athletic eventsbetween 2018 and 2019 in the U16, U18, and U20 categories. In summary, unequal distribution of birth dates per quartile was observed where a greater number of young para-athletes was born in the Q1 of the year for U16 (χ²3= 18.785; p = .0003; Phi effect = .45), U18 (χ²3= 6.846; p= .05; Phi effect = .17), and U20 (χ²3= 10.156; p= .017; Phi effect =.17). However,when we compared the performance of the athletes by event (track and field events) and separately by quartile, no significant difference was found (p> .05). In conclusion, our study evidenced the influential role of relative age in track and field para-athletes, but it seems that this phenomenon is not related to performance in track and field events.(AU)

O Efeito da Idade Relativa (EIR) é um fenômeno caracterizado por uma significativa representação de atletas nascidos nos primeiros meses do ano competitivo na mesma faixa etária que tem sido observada em categorias juvenis de atletismo. No entanto, há ainda uma lacuna em termos de investigaçãopara analisar esse fenômeno e sua relação com o para-desporto. Assim, o obejtivo do presente estudo foi analisar a existência de EIR em atletas jovens de para-atletismo (categorias Sub-16, Sub-18 e Sub-20) e sua relação com o desempenho em eventos atléticos individuais de acordo com o quartil de nascimento (Q1, Q2, Q3 e Q4). As datas de nascimento foram recolhidas de 700 jovens atletas do sexo masculino de paradesporto que participaram de eventos de atletismo individuais entre 2018 e 2019 nas categorias Sub-16, Sub-18 e Sub-20. No geral, observou-se uma distribuição desigual das datas de nascimento por quartil, onde um maior número de jovens para-atletas nasceu no Q1 do ano para Sub-16 (χ²3= 18.785; p = .0003; Phi effect = .45), Sub-18 (χ²3= 6.846; p= .05; Phi effect = .17), e Sub-20 (χ²3= 10.156; p= .017; Phi effect = .17). Entretanto, quando comparamos o desempenho dos atletas por evento (provas de atletismo) e separadamente por quartil, não houve diferenças significativas (p> .05). Em conclusão, nosso estudo evidenciou o papel influente da idade relativa em paraatletas de atletismo, mas parece que esse fenômeno não está relacionadoao desempenho em eventos desta modalidade.(AU)

An unexpected shift in constant year effects in female elite handball.

One of the most convincing studies about the importance of the cutoff date in relative age effects was when Helsen et al. (2000) showed that a shift in the date directly resulted in a change of birth month distributions in soccer. Over the past four decades, the role of the birth year has also been associated with relative age effects (as reflected in constant year effects). In this investigation, two studies attempted to replicate the shift of birth year distributions caused by a change in birth years in international female handball. In Study 1, the results from the female handball world championship 2017 showed a significant within-year effect overall and a constant year effect for players born 1988 and after. A second study was conducted with female players from world championships in 2009, 2011, 2013, and 2015. Results demonstrated small effect sizes for most tests. However, there was an unexpected trend toward a constant year effect shift at the age of 28 years. Several hypotheses are presented as an explanation for this trend.

Temporal origin of mouse claustrum and development of its cortical projections.

The claustrum is known for its extensive connectivity with many other forebrain regions, but its elongated shape and deep location have made further study difficult. We have sought to understand when mouse claustrum neurons are born, where they are located in developing brains, and when they develop their widespread connections to the cortex. We established that a well-characterized parvalbumin plexus, which identifies the claustrum in adults, is only present from postnatal day (P) 21. A myeloarchitectonic outline of the claustrum can be derived from a triangular fiber arrangement from P15. A dense patch of Nurr1+ cells is present at its core and is already evident at birth. Bromodeoxyuridine birth dating of forebrain progenitors reveals that the majority of claustrum neurons are born during a narrow time window centered on embryonic day 12.5, which is later than the adjacent subplate and endopiriform nucleus. Retrograde tracing revealed that claustrum projections to anterior cingulate (ACA) and retrosplenial cortex (RSP) follow distinct developmental trajectories. Claustrum-ACA connectivity matures rapidly and reaches adult-like innervation density by P10, whereas claustrum-RSP innervation emerges later over a protracted time window. This work establishes the timeline of claustrum development and provides a framework for understanding how the claustrum is built and develops its unique connectivity.

Relative Age Effect in Brazilian water polo: analysis of male and female athletes from U16 to senior categories

Abstract Aim: To investigate the existence of relative age effect (RAE) in Brazilian water polo athletes according to sex and age category. Methods: The birthdate of 574 Brazilian water polo athletes were organized according to the athletes' birthdates into quarters of the year (Q1, Q2, Q3, and Q4), and classified according to sex (male and female) and age category (U16, U18, U20, and senior). To verify the existence of RAE, the Chi-Square tests (χ2) were performed, and the effect sizes (ω) were calculated for each of the tests. We also calculated odds ratio (ORs) and 95% confidence intervals, setting the level of significance to 0.05. As post hoc analysis, multiple comparisons between quarters were performed, with Bonferroni's correction (significance level set to 0.0083 in these cases). Results: The results indicated an uneven distribution of birthdates for male water polo athletes (χ2 = 12.257; p = 0.007; ω = 0.173), with an overrepresentation of athletes born in the first (p < 0.006) and second (p < 0.002) quarters. When sex and age category were considered, male athletes presented uneven distributions in U20 (χ2 = 10.747; p = 0.013; ω = 0.345) and senior (χ2= 12.614; p = 0.006; ω = 0.383) categories. In females, no differences were found. Conclusion: We conclude that there is an uneven distribution of birthdates in male Brazilian water polo athletes, indicating the presence of RAE in this group.

Relative Age Effect on Brazilian male elite futsal athletes according to playing position and performance by goals scored on Brazil National Futsal Leagues

Abstract Introduction: The relative age effect is prevalent in different elite team sports. However, little is known about this phenomenon in high-level adult male futsal players. Aim: The present study aimed to investigate the prevalence of relative age effect in Brazilian male elite futsal players, and its relationship with playing position and goals scored on Brazil National Futsal Leagues (BNFL) from 2016 to 2020. Methods: The distribution of birth dates, playing positions, and goals scored by male participants of the Brazil National Futsal Leagues were analyzed. Chi-squared tests were used to analyze the birth dates distribution based on quarters and semesters of the year, according to playing position (defender, winger, pivot, and goalkeeper) and scoring performance (high and low). Results: The overall analysis indicated that the relative age effect is prevalent on the pool of athletes analyzed. However, this effect was position-dependent, since relatively older athletes were overrepresented only in wingers and defenders playing positions. On the other hand, scoring performance was not associated with the relative age effect, since this effect was found in both performance levels. Conclusion: Relative age effects are prevalent in Brazilian male elite futsal athletes, especially for defenders and wingers. Considering the high level of competitiveness for spots in elite futsal teams, coaches and sports administrators must be educated about the prevalence of the relative age effect in this sporting context. This is necessary in order to reduce the inequalities generated by age categories based on arbitrary cut-off dates, which may reduce potential talent loss.

The Relative Age Effect on Anthropometry, Body Composition, Biological Maturation and Motor Performance in Young Brazilian Soccer Players.

The present study aimed to investigate the influence of months of birth on anthropometry, body composition, biological maturation, and motor performance in young Brazilian soccer players. Young Brazilian soccer players from the Under-13 (n = 50; 13.6 ± 0.3 years), Under-15 (n = 50; 15.5 ± 0.4 years), and Under-17 categories (n = 46; 17.7 ± 0.3 years) took part in this study. Athletes were divided according to chronological age, 1st tertile (January to April); 2nd tertile (May to August); and 3rd tertile (September to December). Anthropometry, body composition, biological maturation, and motor performance variables were evaluated for all participants. There were no differences between the U-13, U-15, and U-17 categories regarding birth tertiles (p > 0.05). Differences between the ages and birth tertiles were observed for the stature, body mass, and lean body mass (p < 0.05). Moreover, differences were found in maturational status between the ages and birth tertiles (p < 0.05). In general, U-13 players showed lower values compared to U-15 and U-17 players in tests of motor performance. In addition, there was a difference in motor performance between the birth tertiles only for RSA variables. The months of birth influenced the stature, body mass, lean body mass, and repeated sprint ability in the U-13 and U-15 categories. Thus, care should be taken during the process of talent selection, as many young players could be underestimated due to their date of birth.

Relative Age Effect in 14- to 18-Year-Old Athletes and Their Initial Approach to This Effect-Has Anything Changed Over the Past 10 Years?

One of the environmental variables associated with early talent development and the achievement of a high level of proficiency in sport is the relative age effect (RAE). The purpose of our study was threefold: (a) to calculate the RAE in young Israeli athletes (ages 14-18 years); (b) to examine how the athletes perceived this effect, if the effect indeed exists; and (c) to compare the RAE findings of this study with those of two previous studies on elite male (Lidor et al., 2010) and female (Lidor et al., 2014) Israeli ballplayers. Participants in the current study were 1,397 athletes (390 females and 1,007 males) who competed in five individual (gymnastics, judo, swimming, tennis, and track and field) and five team (basketball, soccer, team handball, volleyball, and water polo) sports. Data on the RAE, as well as on a number of aspects associated with this effect as perceived by the athletes, were collected via two closed questions. Data analyses showed that the RAE was found to be significant among the male athletes in four sports-swimming, basketball, soccer, and team handball; those who were born early in the year had a higher representation in these sport programs. However, this effect was not found to be significant in the female athletes. Most of the female and male athletes did not think that their birth date influenced their athletic success. However, a large portion of those who were born in the first quarter of the year (Q1) and the second quarter of the year (Q2) among the male athletes felt that they exhibited stronger abilities in the sports program compared to their peers who were born in the third and fourth quarters of the year (Q3 and Q4, respectively). The data of the current study provide additional support for the use of an "open door" approach to accepting children to sport programs by policymakers and coaches in Israel.

Leveling the Playing Field: A New Proposed Method to Address Relative Age- and Maturity-Related Bias in Soccer.

Despite various solutions proposed to solve the relative age effect (RAE), it is still a major problem confounding talent identification and selection processes. In the first phase, we sampled 302 under 7-21 academy soccer players from two Belgian professional soccer clubs to explore the potential of a new approach to solve the inequalities resulting from relative age- and maturity-related bias. This approach allocates players into four discrete quartile groups based on the midway point of their chronological and estimated developmental (ED) birth dates (calculated using the growth curves for stature of Belgian youth). With the use of chi square analyses, a RAE was found (p < 0.01) for the overall sample (Q1 = 41.4% vs. Q4 = 14.9%) that completely disappeared after reallocation (Q1 = 26.5%; Q2 = 21.9%; Q3 = 27.5%; Q4 = 24.2%). According to the new allocation method, the stature difference was reduced, on average, by 11.6 cm (from 24.0 ± 9.9 to 12.4 ± 3.4 cm, d = 1.57). Body mass difference between the two methods was 1.9 kg (20.1 ± 11.3-18.2 ± 13.1 kg, respectively, d = 0.15). The new method created a maximum chronological age difference of 1.9 vs. 0.8 years for the current method. With the use of this method, 47% of the players would be reallocated. Twenty-three percent would be moved up one age category, and 21% would be moved down. In the second phase, we also examined 80 UK academy soccer players to explore if reallocating players reduces the within-playing group variation of somatic and physical fitness characteristics. The percentage coefficient of variation (%CV) was reduced (0.2-10.1%) in 15 out of 20 metrics across U11-U16 age categories, with the U13 age category demonstrating the largest reductions (0.9-10.1%) in CV. The U12 and U13 age categories and associated reallocation groupings showed trivial to small (ES = 0.0-0.5) between-method differences and trivial to moderate (ES = 0.0-1.1) differences within the U14-U16 age categories. A reduction in RAE may lead to fewer dropouts and thus a larger player pool, which benefits, in turn, talent identification, selection, and development.

Research in Another un-Examined (RAE) context. A chronology of 35 years of relative age effect research in soccer: is it time to move on?

It is approximately 35 years since the publication of the first relative age effect paper in sport and despite the volume of empirical studies, book chapters, conference presentations, and column inches dedicated to this topic we appear to be no further on in eliminating or attenuating this discriminatory practice. This commentary argues that the ongoing use of univariate methods, focusing on primary or secondary analyses of birth-date data, unearthed from previously un-examined contexts is not conducive to stimulating discussion or providing empirical solutions to relative age effects. This paper concludes by suggesting a departure from the traditionally narrow view of relative age inquiry and instead consider the role of transdisciplinary research.

Combinatorial Developmental Controls on Striatonigral Circuits.

Cortical pyramidal cells are generated locally, from pre-programmed progenitors, to form functionally distinct areas. By contrast, striatal projection neurons (SPNs) are generated remotely from a common source, undergo migration to form mosaics of striosomes and matrix, and become incorporated into functionally distinct sectors. Striatal circuits might thus have a unique logic of developmental organization, distinct from those of the neocortex. We explore this possibility in mice by mapping one set of SPNs, those in striosomes, with striatonigral projections to the dopamine-containing substantia nigra pars compacta (SNpc). Same-age SPNs exhibit topographic striatonigral projections, according to their resident sector. However, the different birth dates of resident SPNs within a given sector specify the destination of their axons within the SNpc. These findings highlight a logic intercalating birth date-dependent and birth date-independent factors in determining the trajectories of SPN axons and organizing specialized units of striatonigral circuitry that could influence behavioral expression and vulnerabilities to disease.

Divergence in parturition timing and vegetation onset in a large herbivore-differences along a latitudinal gradient.

In northern environments, the period of access to high-quality forage is limited, exerting strong selective pressure to optimize the timing of parturition. We analysed timing and variation in moose (Alces alces) parturition dates of 555 females at 18 study sites across 12° of latitude (56-68° N, 1350 km) in Sweden. We found evidence for a spatial match of parturition timing to vegetation onset, but no evidence that moose adjust parturition to vegetation onset in a given year. We found a breakpoint at 64° N. Despite adaptation across latitudes, temporal divergences occurred. Females below 64° N calved after vegetation onset and females above 64° N calved before. Here, parturition before vegetation onset might be a strategy to optimize forage utilization time with the very short growing season. Highly seasonal environments such as at higher latitudes may make it advantageous to adapt parturition towards long-term climatic patterns by matching the most favourable period. Given the direction of temporal divergence, our study suggests that climate change may have less of an impact on moose parturition at northern latitudes than southern latitudes.

Initial axon growth rate from embryonic sensory neurons is correlated with birth date.

Axon growth rate from different populations of sensory neurons is correlated with the distance they have to grow to reach their targets in development: neurons with more distant targets extend axons at intrinsically faster rates. With growth of the embryo, later-born neurons within each population have further to extend their axons to reach their targets than early-born neurons. Here we examined whether the axon growth rate is related to birth date by studying the axon growth from neurons that differentiate in vitro from precursor cells isolated throughout the period of neurogenesis. We first showed that neurons that differentiated in vitro from different precursor cell populations exhibited differences in axon growth rate related to in vivo target distance. We then examined the axon growth rate from neurons that differentiate from the same precursor population at different stages throughout the period of neurogenesis. We studied the epibranchial placode precursors that give rise to nodose ganglion neurons in the chicken embryo. We observed a highly significant, threefold difference in axon growth rate from neurons that differentiate from precursor cells cultured early and late during the period of neurogenesis. Our findings suggest that intrinsic differences in axon growth rate are correlated with the neuronal birth date.

Relative Age Effect in the Girls' Volleyball U18 World Championship.

The relative age effect (RAE), within the sporting scope, refers to the possible advantages of participation and performance of athletes born in the first months of the year of selection in relation to others within the same age category. The aim of the present study was to investigate the RAE in girls' volleyball players participating in the U-18 World Championship, analysing the differences between the medal teams and other teams in the tournament, and considering this phenomenon in relation to the continents. Data collection was obtained from the website of the International Volleyball Federation with a sample made of 1654 youth players in the last six world championships (2007, 2009, 2011, 2013, 2015 and 2017). A greater representation of athletes born in the first months of the year of all the world championships was observed. In the comparison among the continents, it was observed that in Africa, there was a more equal distribution of quartiles compared to America, Asia and Europe. It should be noted that there was a higher percentage of medalist athletes born at the beginning of the year in comparison to the countries that placed in the last three positions of the championship. Therefore, in U-18 female volleyball, there is an advantage to have the closest birth age at the beginning of the competitive biennium.

Different maternal investment strategies for male and female calves in a polygynous mammal.

Maternal effects occur when the phenotype of the mother influences that of the young to the detriment of her survival, growth or fitness. The investment of the mother can be affected by maternal body condition and/or experience. Trivers-Willard Hypothesis (TWH) and Local Resource Competition Hypothesis (LRCH) are the main hypotheses used to explain bias in birth sex-ratios in mammals, as well as for sex-biased maternal investment. Both hypotheses suggest that a different amount of investment must be expected according to the sex of the young. However, recent studies suggest that these differences are not in quantity but in the strategies: mechanisms and objectives may differ for each sex. We studied how maternal characteristics (age, body mass, body condition, and dominance status) influence relevant aspects of the birth and early growth of the calf (birth date, birth body mass, body mass at weaning, and body condition at weaning) separately for each sex; and how that investment is mediated by milk production and composition (lactose, fat, and protein). One hundred eighty-eight newborns from 75 captive red deer hinds aged from 2 to 19 years were analyzed. The main differential investment observed was related to birth date: when producing a female, hinds give birth earlier in the season only if they have a good body condition; however, when gestating a male it is the older hinds those which deliver earlier. Subsequently, milk production and composition are correlated with birth body mass in female calves, but to weaning body mass in males. Thus, only hind body mass affects the weaning body mass of female calves, compared with age and hind body mass in males. These results suggest that while TWH fits the maternal investment strategy found for male calves, it is LRCH which correlates with the maternal investment patterns observed for females.

Anthropometric and Physical Performance of Youth Handball Players: The Role of the Relative Age.

BACKGROUND: The relative age effect is essential throughout all of the talent selection processes in sports, especially during adolescence, which leaves fewer athletes within each cohort that are born late in the selected year. The aim of the present study was to examine the role of relative age in anthropometric and physical performance characteristics of youth handball players by gender. METHODS: The sample that was selected included 47 participants (male n = 23, female n = 24). The data collection included anthropometric, body compositions parameters, and physical performance levels. RESULTS: There was a significantly higher representation of players in the first semester in comparison with the second semester, for all of the gender groups, except for the selected male players. In males, statistically significant differences were found in height, sitting height, weight, wingspan, arm and leg circumferences, and in throws speed (in support and in suspension) between those players that were born in the first and second semester. CONCLUSION: The results confirmed an effect of relative age in the players born in 2002 that were selected to participate in the Spanish Championship, which was different for males and females. In spite of this effect, which only appeared in females, significant differences in the anthropometric and physical conditions appeared in the male players.

The influence of age-policy changes on the relative age effect across the Australian Rules football talent pathway.

OBJECTIVES: To identify the influence of age-policy changes on the relative age effect (RAE) across the Australian Football League (AFL) talent pathway. DESIGN: Retrospective cross-sectional analysis of junior AFL players attending the National Draft (National), State, and State Under 16s (U16) combines between 1999-2016. METHODS: Birth-date data was obtained for players attending the AFL State U16 (n=663, age: 15.9±0.4years), State (n=803, age: 19.1±1.7years), National (n=1111, age: 18.3±0.8years) combines. Corresponding aged-matched Australian general population birth rate data was also collected. RESULTS: A chi-squared analysis comparing birth month distributions found all combine groups differed significantly from the general population (Under 16s: χ2=62.61, State: χ2=38.83, National: χ2=129.13, p<0.001). Specifically, Under 16s had greater birth frequencies for months January to March (≥2%, p<0.05), with more State players born in January (4.9%, p<0.05). Age-policy changes at the National level reduced birth distribution bias for some months, however the RAE remained for March, June and July (3.9%, 6.1%, 4.3%, p<0.05). State U16s and National players had 2-9% lower birth frequencies for November-December births compared general population. CONCLUSIONS: Selection bias exists towards older players is present at the AFL's State U16, and is maintained at State and National level combines. Age-policy changes are only partially successful at addressing the RAE at the National level, with alternative strategies also recommended in order to address the RAE across the AFL talent pathways.

Birth date promotes a tortoise or hare tactic for body mass development of a long-lived male ungulate.

Maternal and early-life influences may affect life-long individual phenotype, potentially influencing reproductive success. However, some individuals may compensate for a poor start to life, which may improve longevity and reproductive success later in life. We developed four models to assess whether maternal characteristics (age, body mass and previous year cumulative lactation demand) and/or birth date influenced a long-lived mammal's phenotype to maturity. We used a directional separation analysis to assess the relative influence of each maternal characteristic and birth date on captive male white-tailed deer (Odocoileus virginianus) body mass and antler size. We found that birth date was the only characteristic that persistently influenced male body mass. Depending on when offspring were born, they used alternative tactics to increase their body mass. Birth date positively influenced body mass at 1, 2 and 3 years of age-indicating males displayed faster growth and compensated for late birth (hare tactic). However, early-, heavy-born males were heavy juveniles, and juvenile body mass positively influenced mature body mass (slow but steady growth; tortoise tactic). Our findings provide a first evidence that a long-lived ungulate can display alternative tactics to achieve heavy body mass; individuals are either born early and heavy and are heavy throughout life (tortoise), or light, late-born individuals compensate for a poor start in life by growing at a faster rate to equal or surpass the body mass of early-born individuals (hare). Either tactic may be viable if it influences reproductive success as body mass positively influences access to mates in ungulates.

Relative age effect, skeletal maturation and aerobic running performance in youth soccer players

To investigate the presence of a relative age effect (RAE) and the influence of birth quarters (BQ), semesters (S) as well as skeletal maturation on anthropometric characteristics and aerobic peak speed (PST-CAR) in youth male soccer players. Methods: One hundred players were recruited to participate in this study. Players were allocated into 4 BQ's and 2 S. Skeletal maturity status was assessed using the Fels method. Assessments for players included determination of body size and composition and PST-CAR. Results: Overall, more players were born in BQ1 (38 %) and S1 (75%). The likelihood of players born in BQ1 and BQ2 being selected was 3.61 to 4.96 times higher than players in BQ3 and BQ4. Players in BQ4 maturing earlier were biologically older than their peers in BQ1. The players in BQ3 and S2 displayed higher PST-CAR compared with players in BQ2 and S1, respectively. However, players of contrasting skeletal maturity status did not differ in aerobic performance. Conclusion: Our findings indicate that coaches and talent scouts are systematically retaining average and early maturing players born in S1 and excluding late maturing players born in BQ4. However, aerobic performance appeared to be dependent on the relative age, but independent of skeletal maturation during puberty.(AU)