Quantification of the relative age effect in three indices of physical performance

Relationship between relative age measured through decimal age, physical variables and anthropometry in elite youth soccer players

INTRODUCTION

Age differences between athletes born in the same year, as well as an over-representation of older players, are known as the Relative Age Effect (RAE). Players born at the beginning of the selection year have a physical and anthropometric advantage over their younger peers. Experts keep looking for new prediction variables for talent identification.

OBJECTIVES

The aim of the study is to correlate anthropometric, strength and power variables with the relative age (RA) and the level of the teams in which players played in each age category.

METHODS

All players (N = 366) from an elite soccer academy of a Spanish club volunteered to participate in the study (U23-U10).

RESULTS

There was a significant correlation between the RA of the players and the level of the team in which they played in each age category but no correlation between trimester of birth and level of the team. We found significant correlations between the players' physical capacities, anthropometry, RA and the level of the team in which they played for the same age category, mainly from U16 to U10. U23 did not show any correlation between RA and physical or anthropometric variables.

CONCLUSION

Coaches should be cautious of choosing players based only on anthropometric or physical attributes.

Relative Age Effect in Physical Fitness during the Elementary School Years

Age-groups are commonly implemented in education and sports in order to provide fair and equal opportunities. Various studies, however, have shown a competitive advantage for early born children over their relatively younger peers, which is referred to as relative age effect. The present study examined differences in various components of physical fitness in Austrian elementary-school children. A total of 18,168 children (51% boys) between 6 and 11 years of age provided valid data on anthropometric characteristics and physical fitness. Specifically, children completed eight fitness tests that assessed cardiorespiratory endurance, muscular strength and power, speed, agility, flexibility and object control. Across age-specific quartiles, older children were significantly taller and heavier than their younger peers. Older children also displayed better performance for strength and power, speed, agility and object control, while differences in cardio-respiratory endurance were less pronounced. These results highlight the presence of a relative age effect during the elementary school years and emphasize the need to consider individual differences in the evaluation of children's performance. As all children should be given equal opportunities to engage successfully in physical education and sports, physical education teachers and youth coaches need to be educated on the implications of a relative age effect.

Relative Age Effects as Evidence of Selection Bias in Major League Baseball Draftees (2013-2018)

ABSTRACT

Herring, CH, Beyer, KS, and Fukuda, DH. Relative age effects as evidence of selection bias in major league baseball draftees (2013-2018). J Strength Cond Res 35(3): 644-651, 2021-The purpose of this study was to examine if relative age effects (RAEs) or the unequal birth-date distribution among a cohort group of individuals exist in Major League Baseball (MLB) draftees. This study comprised 7,078 men drafted in the MLB first-year player draft from 2013 to 2018. Data collected for each draftee included birth date, year drafted, academic-level classification, position, round drafted, batting side, and throwing arm. Draftee's birth dates were categorized into quarters based on the calendar year for baseball in the United States (Q1: August-October; Q2: November-January; Q3: February-April; Q4: May-July). Player birth-date distributions were compared with average expected birth-date distributions and evaluated with the χ2 goodness of fit statistic. Significant χ2 tests were followed up by calculating the standardized residual for each quarter. Differences from the expected frequencies were found for the overall group (p < 0.001) with standardized residuals for baseball athletes born in Q1 (z = +4.45) and Q3 (z = -4.15) exceeding ±2.0. Similar patterns were noted for high schoolers (Q1: z = +3.30; Q3: z = -3.28), pitchers (Q1: z = +2.78; Q3: z = -3.12), early middle rounders (Q1: z = +3.08; Q3: z = -2.67), late rounders (Q1: z = +2.70; Q3: z = -2.61), right-side hitters (Q1: z = +3.23; Q3: z = -2.26), left-handed pitchers (Q1: z = + 2.12; Q3: z = -2.59), and right-handed positional players (Q1: z = +3.12; Q3: z = -2.12). Consistent with the majority of previous research, RAEs are apparent in MLB draftees, with specific patterns of unequal distribution among subsets of athletes.

The Relative Age Effect and Talent Identification Factors in Youth Volleyball in Poland

Previous studies in team sports have not reported evidence regarding the relative age effect (RAE) in relation to the talent identification (TI) process in volleyball, which is organized and controlled by a national federation. Volleyball is a non-contact team sport in which a player’s physique does not directly affect other players in the game but is considered one of the most critical factors in the TI process. The aims of the present study were (1) to determine the differences in the quarterly distribution of age between Polish youth volleyball players from the Olympic Hopes Tournament (OHT) and the general population, (2) to investigate the quarterly differences in anthropometric characteristics and motor test results in OHT participants, and (3) to identify the criteria that determine selection for the National Volleyball Development Program (NVDP). The present study identified the RAE in young male (n = 2,528) and female (n = 2,441) Polish volleyball players between 14 and 15 years of age who competed in the elite OHT in 2004–2015. The study included anthropometric characteristics, motor test results, and selection for the NVDP. The multivariate analysis of covariance demonstrated no significant main effect for birth quarter or calendar age in any of the OHT female players or in male players selected for the NVDP. In the group of non-selected NVDP male players, the analysis demonstrated significant differences by birth quarter as a covariate for body height (F = 0.01, p < 0.001), spike reach (F = 7.33, p < 0.05), and block jump (F = 0.02, p < 0.001). Significant differences by calendar age as a covariate were observed for body mass (F = 0.53, p < 0.01), spike jump (F = 2.64, p < 0.05), block jump (F = 0.4, p < 0.01), and zigzag agility test results (F = 0.01, p < 0.01). The results showed a significant overrepresentation of early-born participants in the OHT and NVDP subsamples. The classification model demonstrated that a combination of four characteristics optimally discriminated between players selected for the NVDP and those who were not selected. This combination of variables correctly classified 77.7% of the female players and 71.8% of the male players in terms of their selection for the NVDP. The results of this study show that jumping ability and body height are crucial in the TI and selection process in youth volleyball.

The relative age effect on physical fitness in preschool children

The aim of the present study was to investigate the existence of a relative age effect (RAE) on physical fitness of preschoolers. Anthropometry and physical fitness were assessed in 3147 children (3-5 years old) using the PREFIT battery. Based on the birth year, participants were divided into 3year groups (3-, 4- and 5-years). Within each year group, 4quarter groups were created: quarter 1, preschoolers born from January to March; quarter 2, from April to June; quarter 3, from July to September; quarter 4, from October to December. The MANCOVA analysis revealed a main effect of year group (Wilks' λ = 0.383; F_10,5996 = 369.64; p < 0.001, η_p ² = 0.381) and of quarter (Wilks' λ = 0.874; F_15,8276.6 = 27.67; p < 0.001; η_p ² = 0.044) over the whole battery of tests. To the best of our knowledge, this is the first study to report the existence of RAE at the preschool stage. In general, performance improved as the relative age increased (i.e., those born in quarter 1 performed better than those in the other quarters). Individualization strategies should be addressed within the same academic year not only in elementary or secondary years but also in preschoolers.

Relative Age Effect of Sport Academy Adolescents, a Physiological Evaluation

The relationship between birth quarter distribution and physiological characteristics related to athletic skills, in adolescent sport academy students has not been fully investigated. In a cross-sectional study, we recruited 86 boys and 52 girls aged 12–14 years during their first term at a sport academy school. We measured body size, cardiac size, pulmonary function, body composition, lower body power, cardiorespiratory fitness parameters, and running endurance by standard methods and analyzed these estimates in relation to birth quarter by ANOVA. Birth quarter distribution in our cohort was compared with birth quarter distribution in the same ages in the whole of Sweden and analyzed by logistic regression. The academy had an overrepresentation of students born in the first quartile of the year compared to those born in the last quartile (odds ratio 2.3 (95% CI: 1.1–4.7)). When comparing the physiological characteristics between birth quarters, uniformity is prominent since out of 26 performed physiological and anthropometric tests only four showed statistically significant group differences. We thus believe that the selection process to the sport academy favours athletes with higher chronological age, i.e., a so-called relative age effect is present.

Influence of the relative age effect on children's scores obtained from the Canadian assessment of physical literacy

BACKGROUND

Age grouping by the imposition of a cut-off date, common in sports and education, promotes a relative age difference that is associated with developmental advantages for children who are born on the "early side" of the cut-off date and disadvantages to those born later in the same year, which is known as the relative age effect (RAE) bias. Acquiring an adequate level of physical literacy is important for children to remain active for life. The Canadian Assessment of Physical Literacy (CAPL) is an assessment protocol that encompasses measures in the domains of children's Daily Behaviours, Physical Competence, Motivation and Confidence, and Knowledge and Understanding. The purpose of this study was to ascertain whether the CAPL scores were susceptible to the RAE, which could affect our interpretation of the CAPL findings.

METHODS

This cross-sectional study examined if scores obtained in the CAPL (i.e., the four domains individually and the total CAPL score) were susceptible to the RAE in children aged 8 to 12 years and, if so, which physical competence assessments (movement skills, cardiorespiratory, strength, muscular endurance, flexibility, and body composition measurements) were more susceptible. Participants (n = 8233, 49.8% boys) from the Royal Bank of Canada-CAPL Learn to Play project from 11 sites in seven Canadian provinces were tested using the CAPL protocol.

RESULTS

Among boys and girls, the RAE was significantly associated with two and three of the four domain scores, respectively, after controlling for covariates. However, effect sizes were negligible for the comparisons between quarters of the year and physical literacy domains and overall scores. For the main effect of the relative age, boys and girls born in the first three months of the year were taller (F(3, 4074) = 57.0, p < 0.001, ƒ2 = 0.04 and F(3, 4107) = 58.4, p < 0.001, ƒ2 = 0.04, respectively) and demonstrated greater muscular strength (F(3, 4037) = 29.2, p < 0.001, ƒ2 = 0.02 and F(3, 4077) = 25.1, p < 0.001, ƒ2 = 0.02, respectively) compared with those born later in the same year.

CONCLUSIONS

Collectively, our results suggest that the RAE bias is mainly negligible with regard to the domain scores and overall CAPL scores in this large sample of children.

Relationships Between Measures of Physical Fitness Change When Age-Dependent Bias is Removed in a Group of Young Male Soccer Players

James, RS, Thake, CD, and Birch, SL. Relationships between measures of physical fitness change when age-dependent bias is removed in a group of young male soccer players. J Strength Cond Res 31(8): 2100-2109, 2017-Age-dependent bias is a key issue within talent identification of children, particularly when measures of physical fitness are used. Coaches in sport would benefit from a relatively straightforward method to remove age-dependent bias, enabling identification of children who are relatively high performers for their age. This study aimed to determine whether removal of age effects caused changes in the relationships between physical performance and anthropometric measures commonly used in talent identification and development systems. Sixty male soccer players, aged 11-17 years, underwent measures of anthropometry, muscular power, strength, sprint speed, and agility. Most absolute measures of performance were significantly correlated with each other, and all performance measures were significantly correlated with age. Age residuals were calculated, for all variables, to determine which players performed relatively well for their age and to investigate age-independent relationships between variables. In general, players with relatively fast sprint performance for their age were taller and had relatively high performance in jump power output and grip strength for their age (r > 0.25 and p < 0.025 in each case). Absolute sprint performance PC1 was significantly correlated with absolute agility performance PC1 (r = 0.473, p < 0.001). However, there was no significant relationship between age-independent measures of agility and any other measures. Usage of age residuals highlights performers that have relatively high physical fitness for their age. Such analyses may assist the talent identification and development processes as long as differential rates of physical development between players are also considered.

The relative age effect reversal among the National Hockey League elite

Like many sports in adolescence, junior hockey is organized by age groups. Typically, players born after December 31^st are placed in the subsequent age cohort and as a result, will have an age advantage over those players born closer to the end of the year. While this relative age effect (RAE) has been well-established in junior hockey and other professional sports, the long-term impact of this phenomenon is not well understood. Using roster data on North American National Hockey League (NHL) players from the 2008–2009 season to the 2015–2016 season, we document a RAE reversal—players born in the last quarter of the year (October-December) score more and command higher salaries than those born in the first quarter of the year. This reversal is even more pronounced among the NHL “elite.” We find that among players in the 90^th percentile of scoring, those born in the last quarter of the year score about 9 more points per season than those born in the first quarter. Likewise, elite players in the 90^th percentile of salary who are born in the last quarter of the year earn 51% more pay than players born at the start of the year. Surprisingly, compared to players at the lower end of the performance distribution, the RAE reversal is about three to four times greater among elite players.

Examining Relative Age Effects in Fundamental Skill Proficiency in British Children Aged 6-11 Years

Birch, S, Cummings, L, Oxford, SW, and Duncan, MJ. Examining relative age effects in fundamental skill proficiency in British children aged 6-11 years. J Strength Cond Res 30(10): 2809-2815, 2016-The relative age effect (RAE) suggests that there is a clustering of birth dates just after the cutoff used for sports selection in age-grouped sports and that in such circumstances, relatively older sportspeople may enjoy maturational and physical advantages over their younger peers. Few studies have examined this issue in nonselective groups of children, and none have examined whether there is evidence of any RAE in skill performance. The aim of this study was to assess whether there were differences in fundamental movement skill (FMS) proficiency within children placed in age groups according to the school year. Six FMS (sprint, side gallop, balance, jump, catch, and throw) were assessed in 539 school children (258 boys and 281 girls) aged 6-11 years (mean age ± SD = 7.7 ± 1.7 years). We examined differences in these FMS between gender groups and children born in different quarters of the year after controlling for age and body mass index (BMI). For balance, chronological age was significant as a covariate (p = 0.0001) with increases in age associated with increases in balance. Boys had significantly higher sprint mastery compared with girls (p = 0.012), and increased BMI was associated with poorer sprint mastery (p = 0.001). Boys had higher catching mastery than girls (p = 0.003), and children born in Q1 had significantly greater catching mastery than those born in Q2 (p = 0.015), Q3 (p = 0.019), and Q4 (p = 0.01). Results for throwing mastery also indicated higher mastery in boys compared with girls (p = 0.013) and that children born in Q1 had higher throwing proficiency than those born in Q4 (p = 0.038). These results are important if coaches are basing sport selection on measures of skilled performance, particularly in object-control skills. Categorizing children's skilled performance based on rounded down values of whole-year age may disadvantage children born relatively later in the selection year, whereas children born earlier in the selection year will likely evidence greater skill mastery and subsequent advantage for selection purposes.

National Strength and Conditioning Association Position Statement on Long-Term Athletic Development

There has recently been a growing interest in long-term athletic development for youth. Because of their unique physical, psychological, and social differences, children and adolescents should engage in appropriately prescribed exercise programs that promote physical development to prevent injury and enhance fitness behaviors that can be retained later in life. Irrespective of whether a child is involved in organized sport or engages in recreational physical activity, there remains a need to adopt a structured, logical, and evidence-based approach to the long-term development of athleticism. This is of particular importance considering the alarmingly high number of youth who fail to meet global physical activity recommendations and consequently present with negative health profiles. However, appropriate exercise prescription is also crucial for those young athletes who are physically underprepared and at risk of overuse injury because of high volumes of competition and an absence of preparatory conditioning. Whether the child accumulates insufficient or excessive amounts of exercise, or falls somewhere between these opposing ends of the spectrum, it is generally accepted that the young bodies of modern day youth are often ill-prepared to tolerate the rigors of sports or physical activity. All youth should engage in regular physical activity and thus should be viewed as "athletes" and afforded the opportunity to enhance athleticism in an individualized, holistic, and child-centered manner. Because of emerging interest in long-term athletic development, an authorship team was tasked on behalf of the National Strength and Conditioning Association (NSCA) to critically synthesize existing literature and current practices within the field and to compose a relevant position statement. This document was subsequently reviewed and formally ratified by the NSCA Board of Directors. A list of 10 pillars of successful long-term athletic development are presented, which summarize the key recommendations detailed within the position statement. With these pillars in place, it is believed that the NSCA can (a) help foster a more unified and holistic approach to long-term athletic development, (b) promote the benefits of a lifetime of healthy physical activity, and

Maturational and social factors contributing to relative age effects in school sports: Data from the London Youth Games

Few studies have investigated whether relative age effects (RAEs) exist in school sport. None have sought to test the competing maturational and social-agent hypotheses proposed to explain the RAE. We aimed to determine the presence of RAEs in multiple school sports and examine the contribution of maturational and social factors in commonplace school sports. We analyzed birth dates of n=10645 competitors (11-18 years) in the 2013 London Youth Games annual inter-school multisport competition and calculated odds ratio (OR) for students competing based on their yearly birth quarter (Q1-Q4). Multivariate logistic regression was used to determine the relative contribution of constituent year (Grade) and relative age in netball and football which used multiyear age groupings. In girls, RAEs were present in the team sports including hockey, netball, rugby union, cricket and volleyball but not football. In boys, RAEs were stronger in common team sports (football, basketball cricket) as well as athletics and rowing. In netball and football teams with players from two constituent years, birth quarter better-predicted selection than did constituent year. Relatively older players (Q1) from lower constituent years were overrepresented compared with players from Q3 and Q4 of the upper constituent years. RAEs are present in the many sports commonplace in English schools. Selection of relatively older players ahead of chronologically older students born later in the selection year suggests social agents contribute to RAEs in school sports.

Relative Age Effects in Dutch Adolescents: Concurrent and Prospective Analyses

The literature on relative age position effects is rather inconsistent. In this study we examined intra-classroom age position (or relative age) effects on Dutch adolescents' school progress and performance (as rated by teachers), physical development, temperamental development (fear and frustration), and depressive symptoms, all adjusted for age at the time of measurement. Data were derived from three waves of Tracking Adolescents' Individuals Lives Survey (TRAILS) of 2230 Dutch adolescents (baseline mean age 11.1, SD = 0.6, 51% girls). Albeit relative age predicted school progress (grade retention ORs = 0.83 for each month, skipped grade OR = 1.47, both p<.001), our key observation is the absence of substantial developmental differences as a result of relative age position in Dutch adolescents with a normative school trajectory, in contrast to most literature. For adolescents who had repeated a grade inverse relative age effects were observed, in terms of physical development and school performance, as well as on depressive symptoms, favoring the relatively young. Cross-cultural differences in relative age effect may be partly explained by the decision threshold for grade retention.

Prediction of habitual physical activity level and weight status from fundamental movement skill level

Fundamental movement skills (FMS) have been assessed in children in order to investigate the issues of the low proportion of children who meet physical activity (PA) guidelines and rising levels of obesity. The aim of this research was to identify whether previous or current FMS level is a better predictor of PA levels and weight status in children. In January 2012 (year 1), 281 children were recruited from one primary school in the West Midlands, UK. Children performed eight FMS three times, which were videoed and assessed using a subjective checklist. Sprint speed and jump height were measured objectively. Height and mass were measured to calculate the body mass index to determine the weight status. Skinfold calliper readings were used to calculate body fat percentage. One year later, in January 2013, all these tests were repeated on the same children, with the additional collection of PA data via the use of pedometers. Following multiple linear regression, it was identified that prior mastery in FMS was a better predictor of current PA, whereas current FMS was a better predictor of current weight status. Overall, FMS mastery is needed in childhood to be able to participate in PA and maintain a healthy weight status.