Background: Does early specialization facilitate later athletic excellence, or is early diversification better? This is a longstanding theoretical controversy in sports science and medicine. Evidence from studies investigating athletes’ starting age, childhood/adolescent progress, and amounts of coach-led practice and peer-led play in their main sport and in other sports has been mixed. Each participation variable was positively correlated with performance in some studies but uncorrelated or negatively correlated with performance in others. However, samples were heterogeneous in age, sports, and performance levels.Objective: This study aimed to establish robust, generalizable findings through a systematic review and meta-analysis. We investigated three questions: (1) did higher- and lower-performing athletes differ in childhood/adolescent progress, starting age, or amounts of main-sport or other-sports practice or play; (2) do effects differ between junior and adult athletes, compared performance levels, or types of sports; and (3) are effect sizes from different predictors associated with one another?Methods: We conducted a systematic literature search in SPORTDiscus, ERIC, ProQuest, PsycINFO, PubMed, Scopus, WorldCat, and Google Scholar until 28 February 2021. Selection criteria included original research studies comparing higher- versus lower-performing athletes regarding one or more of our predictor variables within defined age categories, sports, and sex, and reporting effect sizes or data needed to compute effects sizes. Mean meta-analytic Cohen’sdwas calculated for each predictor. Quality of evidence was evaluated using GRADE.Results: In total, 71 study reports met all eligibility criteria and included 262 international athlete samples, 685 effect sizes, and a total sample size of 9241 athletes from local to Olympic competition level and from diverse sports. The following findings emerged. (1) Compared with their national-class counterparts, adult world-class athletes had more childhood/adolescent multi-sport coach-led practice, a later main-sport start, less main-sport practice, and slower initial progress (|0.23|< $$\bar{d }$$d¯ <|0.50|; allp < 0.001). (2) The opposite was true for predictors of junior-age performance: higher-performing juniors had an earlier main-sport start, more main-sport practice, less other-sports practice, and faster initial progress (|0.23|< $$\bar{d }$$d¯ < |0.61|; allp < 0.001). (3) Main-sport or other-sports peer-led play had negligible effects (allp > 0.05). (4) Results were robust across types of sports. (5) Effect sizes from different predictors were associated with one another (|0.64|< r <|0.79|). A GRADE assessment revealed a low quality of evidence for peer-led play but a moderate to high quality of evidence for all other predictors.Discussion: Excess childhood/adolescent specialized practice may hinder athletes’ long-term development through overuse injury, burnout, suboptimal athlete–sport match, and limiting long-term learning capital. By contrast, adult world-class athletes’ childhood/adolescent multi-sport practice with reduced main-sport practice implied a relatively resource-preserving, cost-reducing, and risk-buffering pattern that yielded greater long-term sustainability and practice efficiency.

Background: To what extent does the pathway to senior elite success build on junior elite success? Evidence from longitudinal studies investigating athletes’ junior-to-senior performance development is mixed; prospective studies have reported percentages of juniors who achieved an equivalent competition level at senior age (e.g., international championships at both times) ranging from 0 to 68%. Likewise, retrospective studies have reported percentages of senior athletes who had achieved an equivalent competition level at junior age ranging from 2 to 100%. However, samples have been heterogeneous in terms of junior age categories, competition levels, sex, sports, and sample sizes. Objective: This study aimed to establish more robust and generalizable findings via a systematic review and synthesis of findings. We considered three competition levels—competing at a national championship level, competing at an international championship level, and winning international medals—and addressed three questions: (1) How many junior athletes reach an equivalent competition level when they are senior athletes? (2) How many senior athletes reached an equivalent competition level when they were junior athletes? The answers to these questions provide an answer to Question (3): To what extent are successful juniors and successful seniors one identical population or two disparate populations? Methods: We conducted a systematic literature search in SPORTDiscus, ERIC, ProQuest, PsychInfo, PubMed, Scopus, WorldCat, and Google Scholar until 15 March 2022. Percentages of juniors who achieved an equivalent competition level at senior age (prospective studies) and of senior athletes who had achieved an equivalent competition level at junior age (retrospective studies) were aggregated across studies to establish these percentages for all athletes, separately for prospective and retrospective studies, junior age categories, and competition levels. Quality of evidence was evaluated using the Mixed Methods Appraisal Tool (MMAT) version for descriptive quantitative studies. Results: Prospective studies included 110 samples with 38,383 junior athletes. Retrospective studies included 79 samples with 22,961 senior athletes. The following findings emerged: (1) Few elite juniors later achieved an equivalent competition level at senior age, and few elite seniors had previously achieved an equivalent competition level at junior age. For example, 89.2% of international-level U17/18 juniors failed to reach international level as seniors and 82.0% of international-level seniors had not reached international level as U17/18 juniors. (2) Successful juniors and successful seniors are largely two disparate populations. For example, international-level U17/18 juniors and international-level seniors were 7.2% identical and 92.8% disparate. (3) Percentages of athletes achieving equivalent junior and senior competition levels were the smallest among the highest competition levels and the youngest junior age categories. (4) The quality of evidence was generally high. Discussion: The findings question the tenets of traditional theories of giftedness and expertise as well as current practices of talent selection and talent promotion. A PRISMA-P protocol was registered at https://osf.io/gck4a/.

Background: Does younger involvement in talent promotion programs (TPPs) facilitate the attainment of higher performance levels? This question is the subject of the present meta-analysis. Many national sport systems have established TPPs such as federations’ junior squads (including under-age selection teams) and youth sport academies, and many are making expanding investments in TPPs. TPPs seek to select the most advanced youth high performers at young ages, around puberty or younger, and then strive to further accelerate their performance development. However, studies show 25–55% annual athlete turnover within TPPs. In this context, accelerated biological maturation (puberty, growth spurt), high relative age within one’s birth year, and intensified sport-specific childhood/adolescent practice may boost rapid junior performance, but the effects diminish or are reversed by adulthood. Moreover, expanded opportunity costs and risks (time demands, injury, burnout) imposed on young TPP participants may impair their long-term development and even prematurely terminate their career. Objective: We aimed to provide robust and generalizable evidence on the effects of early talent promotion on junior and senior performance through a systematic review and meta-analysis. Methods: A systematic literature search was conducted 18/03–03/04/2023 in SPORTDiscus, ProQuest, PsycINFO, PubMed, Scopus, WorldCat, and Google Scholar. We searched for original studies that compared athletes across defined higher and lower performance levels within defined types of sports, age categories, and sexes, regarding their age at commencement of TPP involvement and reported effect sizes or data needed to compute effects sizes. Mean meta-analytic Cohen’s $$\overline{d }$$d ¯ was computed separately for junior and senior athletes. Quality of evidence was evaluated using the mixed-methods appraisal tool. Results: The search yielded k = 51 effect sizes from N = 6233 athletes from a wide range of countries and sports, 82% male and 18% female, from 2009 to 2022. The central finding is that effects on short-term junior performance versus long-term senior performance are opposite, whereby higher-performing junior athletes began TPP involvement at younger ages than lower-performing junior athletes, $$\overline{d }$$d ¯ = − 0.53. In contrast, higher-performing senior athletes began TPP involvement at older ages than lower-performing senior athletes, $$\overline{d }$$d ¯ = 0.56. The findings are robust across different TPPs (federation’s junior squad/selection team, youth academy), individual and team sports, and performance levels compared (international, national, regional). The quality of primary studies was high. Discussion: The findings are consistent with recent meta-analytic evidence that participation patterns predicting early junior success versus long-term senior success are opposite (starting age, main-sport and other-sports practice amounts, age to reach performance ‘milestones’). We discuss theoretical and practical implications of potential selection and ‘treatment’ effects of TPPs. Conclusions: Consistent across different populations, early TPP involvement is positively correlated with short-term junior performance but is negatively correlated with long-term senior performance.

Background: To what extent does junior athletic performance predict senior athletic performance (i.e., in the highest, open-age category)? This question is the subject of a lively debate in the literature. Following traditional theories of giftedness and expertise, some researchers and practitioners have proposed that a high level of junior performance is a prerequisite for the development of a high level of later senior performance. Sceptics of this view hold that junior performance has limited predictive value for later senior performance, pointing to empirical evidence indicating that predictors (e.g., participation patterns) of junior performance and of senior performance differ. The straightforward way to resolve this controversy empirically is to test the correlation between junior and senior performance. Objective: To provide robust and generalizable evidence on this issue, we performed a systematic review and meta-analysis of relevant studies. The aim was to quantify the overall correlation between junior and senior performance and then test whether correlations vary across junior age categories and subsamples (e.g., types of sports). Methods: A systematic literature search was conducted in SPORTDiscus, Eric, ProQuest, PsychInfo, PubMed, Scopus, WorldCat, and Google Scholar from 27 January through 30 April 2022. We searched for original studies that recorded athletes’ junior and senior performance longitudinally and included measures of association between junior and senior performance. Quality of evidence was evaluated using the Mixed Methods Appraisal Tool version for nonrandomized studies. Results: The search yielded k = 129 effect sizes from N = 13,392 athletes from a wide range of Olympic sports, 62% male and 38% female, from 2006 to 2021. Four central findings emerged: (1) Overall, the meta-analytic pooled correlation between junior and senior performance was $$\overline{r }$$r ¯ = 0.148. That is, junior performance explained only 2.2% of the reliable variance in senior performance. (2) The finding was robust across types of sports, sexes, wider or narrower performance ranges, national or international samples, and binary or continuous performance measures. (3) Effects varied across junior age categories: the younger the junior age category, the lower the correlation between junior and senior performance, with $$\overline{{r} }$$r ¯ ranging from $$\overline{{r} }$$r ¯ = − 0.052 to $$\overline{{r} }$$r ¯ = 0.215. That is, across junior age categories, junior performance explained 0–4.6% of the reliable variance in senior performance. (4) The quality of primary studies was high. Discussion: The results suggest that junior performance has very little, if any, predictive value for senior performance. The findings run counter to claims from traditional theories of both giftedness and expertise. From an applied perspective, talent selection typically begins around puberty or younger—age ranges where youth performance is uncorrelated or negatively correlated with later senior performance. The evidence presented here raises serious questions about the use of junior performance for talent selection purposes. A PRISMA-P protocol was registered at https://osf.io/gck4a/.

Retiring professional athletes face multifaceted changes and potential issues of adjustment, occupational development, and well-being, which raises concerns around the world. The study systematically reviewed the available research investigating professional soccer players’ sport retirement from social sciences perspectives. The literature search in electronic databases and a “snowballing” procedure yielded 17 eligible studies investigating > 2,200 retired professional soccer players. The review followed the PRISMA statement. Nine studies focused on an early transition phase to retirement period; four studies investigated later periods of ten years or longer after retirement. Around half of the players reported involuntary retirement, often associated with declining performance and/or injury. Studies suggest issues of adjustment and mental health during early years after retirement, while psychological issues had apparently declined around 1–2 decades after retirement. However, available studies had notable limitations including lack of evidenced representative samples, report of measures’ reliability, and control for confounders. Furthermore, while theoretical models emphasise a holistic perspective, quantitative research often took a narrow rather than holistic perspective. In summary, available knowledge is fraught with some uncertainty regarding reliability and representativeness of the population of retired professional soccer players. We offer future directions to advance the development of a theory of sport retirement.

We explored associations of elite athletes’ multi-year efficiency of practice and improvement of performance with their current and earlier participation patterns. Participants were 80 adult German track-and-field national-squad athletes. Performance improvement was measured as development of athletes’ highest track-and-field championship level and placing from 19 to 25 years (t ₁-t ₂). Practice efficiency was defined as performance improvement per amount of coach-led athletics practice from t ₁ to t ₂. Participation variables included amounts of coach-led practice and peer-led play in athletics and other sports through t ₁ and t ₁-t ₂. Analyses involved an advanced machine learning procedure, XGBoost, allowing non-linear, multivariate exploration. We computed two models, one for performance improvement (“good” discriminative performance, AUC = 0.82) and one for practice efficiency (“fair”, AUC = 0.73). Four central findings emerged: 1. Childhood/adolescent coach-led multi-sport practice was a critical discriminator of adult practice efficiency and performance improvement. 2. Associations were non-linear, displaying a saturation pattern. 3. The likelihood of achieving high adult practice efficiency was greatest when combining ~1,000–2,500 track-and-field practice hours until t ₁ with ~1,250 other-sports practice hours until t ₁. 4. Peer-led engagement in any sport had negligible effects. Childhood/adolescent multi-sport coach-led practice apparently facilitated long-term sustainability of athletes’ development of adult practice efficiency and performance improvement in athletics.