Stephen Cobley

Annual age-grouping and athlete development: a meta-analytical review of relative age effects in sport.

Annual age-grouping is a common organizational strategy in sport. However, such a strategy appears to promote relative age effects (RAEs). RAEs refer both to the immediate participation and long-term attainment constraints in sport, occurring as a result of chronological age and associated physical (e.g. height) differences as well as selection practices in annual age-grouped cohorts. This article represents the first meta-analytical review of RAEs, aimed to collectively determine (i) the overall prevalence and strength of RAEs across and within sports, and (ii) identify moderator variables. A total of 38 studies, spanning 1984–2007, containing 253 independent samples across 14 sports and 16 countries were re-examined and included in a single analysis using odds ratios and random effects procedures for combining study estimates. Overall results identified consistent prevalence of RAEs, but with small effect sizes. Effect size increased linearly with relative age differences. Follow-up analyses identified age category, skill level and sport context as moderators of RAE magnitude. Sports context involving adolescent (aged 15–18 years) males, at the representative (i.e. regional and national) level in highly popular sports appear most at risk to RAE inequalities. Researchers need to understand the mechanisms by which RAEs magnify and subside, as well as confirm whether RAEs exist in female and more culturally diverse contexts. To reduce and eliminate this social inequality from influencing athletes’ experiences, especially within developmental periods, direct policy, organizational and practitioner intervention is required.

Towards a unified understanding of relative age effects

Abstract When athletes are placed into annual age groups to organize and coordinate sport participation, certain (dis)advantages occur as a result of the subtle age differences within these groups. These differences, termed “relative age effects”, have been consistently related to youth and adult sport attainment. However, there has been a lack of consistency in the terminology used in this area of research. In this paper, we consider the operational terms used in relative age research, discuss appropriate applications of terminology, and suggest directions for future research. Importantly, we argue for a unified understanding of what “relative age” means, stressing the need for clarity in directing future advances in the field.

What do we know about early sport specialization? Not much!

In November 2005, the International Olympic Committees Medical Commission issued a statement on Training the elite child athlete recommending that “more scientific research be done to better identify the parameters of training the elite child athlete”. This paper focuses on a specific issue related to training the child athlete: early specialization. While associations between early specialization and expertise development are highlighted, much research also suggests early specialization is associated with a range of negative consequences affecting physical, psychological, and social development. Alternately, some researchers have proposed that an early diversification approach does not disadvantage athletes in acquiring expertise, and is important for the development of intrinsic motivation and skill transferability. However, this review suggests that inadequate evidence exists to resolve the issue in favor of either approach.

Relative age effects in professional German soccer: A historical analysis

Abstract Relative age effects (RAEs) refer to the specific selection, participation and attainment (dis)advantages which occur as a result of physical and cognitive differences within annual age-grouped cohorts. The present study tracked the existence of RAEs in professional German soccer by examining RAEs in players, head coaches and referees who represented professional soccer clubs or officiated in the Bundesliga from 1963/64 to 2006/07. An additional objective was to consider the social-cultural mechanisms responsible for RAEs, so for a similar period, population and soccer participation information was also obtained. When players were categorised into half decade groups, chi-square analyses predominantly showed RAEs across the history of the Bundesliga, irrespective of dates used for annual age grouping in junior/youth soccer. RAEs were also apparent for head coaches but not for referees. Participation data indicated consistent and progressive growth from 1950 to 1990. RAEs influence the likelihood of attaining professional player and coaching status in German soccer. With many coaches being former players, inequalities associated with annual age-grouping appear to extend beyond a playing career. Officiating was not affected, with referees suggested to emerge from an alternative development pathway. Increased popularity of soccer may have propagated RAEs over time, through intensification of competition and selection mechanisms.

Stressors, coping, and coping effectiveness: Gender, type of sport, and skill differences

Abstract The aim of this study was to examine stressors, coping, and coping effectiveness as a function of gender, type of sport, and skill. The sample consisted of 749 undergraduate athletes (455 males, 294 females) aged 18 – 38 years (mean = 19.8 years). Skill was classified as international/national, county, university, and club standard. Participants completed a stressor and coping concept map (Novak & Gowin, 1984). The results revealed gender, type of sport, and skill differences in relation to stressor frequencies, coping strategy deployment, and coping effectiveness. In contrast to previous research, females used a variety of problem-focused (e.g. planning, communication, technique-orientated coping) strategies more frequently than males. Team sport athletes reported a variety of sport-specific stressors relating to the demands of playing in a team environment. The group of national/international athletes reported using more planning, blocking, and visualization, and also reported that their coping was more effective than that of less-skilled athletes.

Relative age effects on physical education attainment and school sport representation

Background: The ‘Relative Age Effect’ (RAE) has consistently been demonstrated to influence attainment in various contexts. In education, RAE appears to provide an advantage to those born during initial months of an academic year, compared with those born in later months. A similar effect has been noted in many sports, with those born shortly after a ‘cut-off’ date being over-represented compared to those born later in the year. Purpose: To determine if ‘relative age’ influenced attainment in physical education (PE) as well as school sport representation in a Key Stage 3 secondary school setting. Participants and setting: For the year 2003–2004, PE attainment data and sport participation records of 621 pupils (317 male, 304 female) aged 11–14 years old, at a large secondary school in the North of England were collated and analyzed. The school contained over 1300 pupils enrolled across Key Stages 3 and 4. During 2004, the school was rated as ‘very good’ in its educational provision by The Office for Standards in Education (OFSTED). Pupil attainment across the core subjects of English, Maths and Science was reported as similar to national averages, while the schools Physical Education (PE) provision was rated as ‘above the national average’. Research design: The research design was cross-sectional in nature, with its goal of assessing present patterns of PE attainment and sport participation in a case-study school. Data collection: Following institutional ethical approval and school consent, annual school records relating to pupils in Key Stage 3 were collected and examined. These records documented social-demographic details including gender, date of birth as well as attainment records of the pupil. PE attainment in Key Stage 3 was based upon observational assessments by PE teachers, where mark allocations reflected the degree of pupil progress and attainment in the academic year. The school PE department was also asked to provide sport participation information. Specifically, which pupils had represented the school at least twice in the sports of soccer, rugby, netball and rounders. Data analysis: Date of birth was coded into quartiles (i.e. three-month categories) to represent relative age. A two-way between group analyses of covariance (ANCOVA) was used to examine the influence of birth date and year group on PE attainment, while Chi-square analyses examined the relationship between date of birth and school sport representation. Findings: Main effects for birth-date (i.e. quartile) and year group on attainment in PE were found as were interactions between gender and year group. Observations of school sport representation data found higher frequencies of pupils born in the first quartile were representing the school across gender and sports. Conclusions: Current age-grouping, assessment and selection strategies in school may be compounding RAEs inside and outside the classroom. School PE and sport environments may be facilitating attainment and representation for the relatively few older individuals in each year group, whilst simultaneously disaffecting a high proportion of relatively younger pupils.

Circumstantial development and athletic excellence: The role of date of birth and birthplace

Abstract Researchers are only beginning to understand how contextual variables such as date of birth and birthplace affect the development of elite athletes. This article considers the generality of birthplace and date-of-birth effects in varying sport contexts. The Study 1 examined how environmental factors associated with an athletes date-of-birth and size of birthplace predict the likelihood of becoming an Olympic athlete in Canada, the United States of America, Germany, and the United Kingdom. Study 2 examined date-of-birth and birthplace effects among athletes playing in the first professional league in Germany. Study 2 also examined the validity of birthplace as a proxy for early developmental environment by comparing birthplace with the place of first sports club in four German sports leagues. Results from both studies showed no consistent findings for date of birth. Findings from Study 2 also suggested incongruence between birthplace and location of first sports club as proxies for early developmental environment. Although there was some consistency suggesting elite athletes are less likely to come from very small or excessively large communities, exceptions occurred both within and across sport contexts. These results suggest that any developmental effects of date and place of birth are buffered by broader socio-cultural factors.

A longitudinal evaluation of anthropometric and fitness characteristics in junior rugby league players considering playing position and selection level

OBJECTIVES The current study provided a longitudinal evaluation of the anthropometric and fitness characteristics in junior rugby league players across three annual-age categories (i.e., under 13s, 14s and 15s) considering playing position and selection level. DESIGN Longitudinal design. METHODS Eighty-one junior rugby league players selected to a talent development programme were tracked over a two year period. Anthropometric (height, sitting height, body mass and sum of four skinfolds) and fitness (lower and upper body power, speed, change of direction speed and maximal aerobic power) characteristics were measured on three occasions (i.e., under 13s, 14s and 15s). Repeated measures multivariate analysis of variance (MANOVA) and multivariate analysis of covariance (MANCOVA; controlling chronological and maturational age) analysed changes across annual-age categories in relation to playing position and selection level. RESULTS Findings identified significant improvements in anthropometric and fitness characteristics across annual-age categories (p<0.001). MANOVA and MANCOVA analysis identified significant overall effects for playing position (p<0.001) and selection level (p<0.05) throughout the two year period. Interactions between playing position and time were identified for height, vertical jump and estimated V˙O2max (p<0.05). Selection level by time interactions were identified for 20m, 30m and 60m sprint (p<0.05). CONCLUSIONS This study demonstrates the improvement of anthropometric and fitness characteristics within junior representative rugby league players. Interactive effects for playing position and selection level by time highlight the variation in the development of characteristics that occur during adolescence. Tracking the progression of characteristics longitudinally during adolescence, instead of at one-off time points, may assist selection and/or performance assessments within rugby league and other youth sport contexts.

Born at the wrong time: selection bias in the NHL draft.

Relative age effects (RAEs) occur when those who are relatively older for their age group are more likely to succeed. RAEs occur reliably in some educational and athletic contexts, yet the causal mechanisms remain unclear. Here we provide the first direct test of one mechanism, selection bias, which can be defined as evaluators granting fewer opportunities to relatively younger individuals than is warranted by their latent ability. Because RAEs are well-established in hockey, we analyzed National Hockey League (NHL) drafts from 1980 to 2006. Compared to those born in the first quarter (i.e., January–March), those born in the third and fourth quarters were drafted more than 40 slots later than their productivity warranted, and they were roughly twice as likely to reach career benchmarks, such as 400 games played or 200 points scored. This selection bias in drafting did not decrease over time, apparently continues to occur, and reduces the playing opportunities of relatively younger players. This bias is remarkable because it is exhibited by professional decision makers evaluating adults in a context where RAEs have been widely publicized. Thus, selection bias based on relative age may be pervasive.

Variations in relative age effects in individual sports: Skiing, figure skating and gymnastics

Abstract In many sports, policy-makers and administrators employ annual cohorts to reduce differences between athletes during childhood and youth. Although well-intended, unintended relative age effects (RAEs) usually occur. RAEs refer to the specific selection, participation and attainment disadvantages associated with participants’ birthdates relative to an arbitrary ‘cutoff’ date used to group participants within annual age groups. To date, we have little understanding of RAEs in individual sports. In this article, Study 1 considered the presence of RAEs in 1474 ski jumping, 7501 cross-country skiing, 15,565 alpine skiing, 4179 snowboarders and 713 Nordic combined athletes. Chi-square analyses revealed significant RAEs for most of these contexts across sexes. In Study 2, RAEs in the aesthetic sports of figure skating (n=502) and female gymnastics (n=612) were considered. There was no effect for the figure skaters and an atypical effect for the gymnasts. The significant effects across most ski sports coupled with the null effects in figure skating and atypical effect in gymnastics suggest that sport-specific contextual factors are important elements in understanding the mechanisms of RAEs, although further work is necessary to validate these findings.