Quantifying the Extent to Which Successful Juniors and Successful Seniors are Two Disparate Populations: A Systematic Review and Synthesis of Findings
Authors: Güllich Arne , Barth Michael , Macnamara Brooke N. , Hambrick David Z. 
Published: April 2023

Abstract
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/.