The core concept of the Fukuoka L-TID model revolves around the “Identification,” “Development,” and “Matching” of athletic potential among primary and secondary school students in Fukuoka Prefecture (15). The programme begins by providing all participants with detailed feedback based on physical fitness test results to promote future skill development and suggest suitable sports aligned with individual strengths. To maximise the opportunity for selected participants to progress to higher levels, they engage in a specialised Physical Ability Development Programme. The programme aims to cultivate athletic potential and develop the skills needed for high-level competition through three main components: the Physical Ability Development Programme (focuses on developing coordination and movement skills through diverse sport experiences including rugby, fencing, and judo), the Intellectual Ability Development Programme (enhances communication skills and logical thinking through lectures on topics such as sports nutrition and mental training), and the Parent Support Programme (equips parents with knowledge in nutrition and sports science to support the athlete's daily life). This comprehensive, multi-dimensional approach, developed in cooperation with various sports organisations, enables athletes to explore a wide range of sporting experiences and ultimately identify the sport that best matches their individual potential.

The Fukuoka L-TID cohort, similar to other Japanese L-TID initiatives, is composed of individuals who exhibit superior athletic ability compared to age-matched Japanese general peers (13, 14). This group is determined through a rigorous three-stage selection process, with physical fitness assessments integrated into each round. Considering that the number of applicants for the initial selection round has sometimes exceeded 50,000, from which approximately 30 athletes are ultimately selected (16), this process clearly functions as a highly competitive and advanced screening for athletic potential (Table 1).

Between 2005 and 2019, a total of 383 athletes (182 males and 201 females) graduated from Fukuoka L-TID programme. Among them, 31 (6 males, 25 females) advanced to the Elite stage by representing Japan at the senior level (defined as “elite athletes”), while the remaining 352 (176 males, 176 females) participated only at the Talent stage as “talented athletes” in accordance with the Japanese FTEM framework (11). Elite achievement was attained by 3.3% of male participants and 12.4% of female participants. The study received ethics approval from the first author's Institute Ethics Committee (Approval Number: 2022-012) and was conducted in accordance with the Declaration of Helsinki.

Initially, the anthropometric and physical fitness indices of the subjects, using measures comparable to the national standard, were compared with those of Japanese age-matched general peers to verify their level. Subsequently, this study examined the characteristics of athletes during elementary and junior high school at two developmental stages (i.e., Talent and Elite), focusing on the following aspects: (1) sporting history and sports transitioning; (2) RAE distribution by birth quarter; (3) anthropometric and physical fitness development.

Participants' sporting histories from elementary through high school were systematically recorded. The final main sport was defined as the most recently recorded sport in which the participants was actively engaged. Sports transitioning was categorised based on continuity between early and later sport participation: individuals were classified as having “continued in the same sport” if the sport engaged in during elementary school matched their final main sport, and as having “transitioned to a new sport” if these differed. Cases where early sport participation data was unavailable or unclear were categorized as “unconfirmed”.

The birth dates were recorded at the time of L-TID application, when they were in the 4th grade of elementary school. Birth months were grouped based on the Japanese fiscal year (Q1: April to May, Q2: June to September, Q3: October to December, and Q4: January to March), following Nakata & Sakamoto (17, 18) and Sasano et al. (19).

Physical and fitness measures were collected from 5th grade of elementary school to 3rd year of junior high school (9th grade), including height, body mass, 25-m sprint, standing broad jump, standing quintuple jump, rebound drop-jump, reaction time, and 20-m shuttle run. The testing were conducted in strict adherence to national standard protocols, the MEXT's New Physical Fitness Test Guidelines (20), were used for height, body mass, standing broad jump, and 20-m shuttle run. Validated protocols were used for the remaining measures (21–23). Trained physical education teachers and the programme graduates administrated all the measures under supervision to ensure standardisation. Sample sizes varied by measure, as not all athletes completed every test.

Hedges' g (24) was calculated to determine the effect sizes (ES) for differences between all subjects (entire cohort) and age-matched Japanese general peers (25). The resulting ES magnitudes were interpreted using Cohen's criteria (26), defining “medium” effects as 0.5 ≤ |g| < 0.8 and “large” effects as |g| ≥ 0.8. Frequencies and proportions were calculated for sporting history. Birth quarter distributions were compared against even distribution using a χ² goodness-of-fit test. Odds Ratios (OR) and 95% Confidence Intervals (95% CI) were computed. To identify ORs differentiating elite athletes (E) from talented athletes (T), logistic regression was conducted for each grade. The dependent variable was the elite status (Elite = 1, Talented = 0). Independent variables included: Sex (Female = 1, Men = 0), Sports transitioning (Yes = 1, No = 0), Birth month (Early = Q1 and Q2 = 1, Late = Q3 and Q4 = 0), Sport type (Individual = 1, Team = 0), Height, Body mass, 25-m sprint, Standing broad jump, Standing quintuple jump, Rebound drop-jump, Reaction time, and 20-m shuttle run. A forward stepwise selection method was employed to construct the most appropriate model for each grade level. The model goodness-of-fit was assessed using the Nagelkerke R² and Chi-square (χ²) statistics. The significance of individual predictors was evaluated using the Wald statistic. Results are presented as ORs with their corresponding 95% CI. Statistical significance was set at P < .05. The various statistical values were interpreted with references to previous research (26, 27).

The cgs sports investigated in this study (i.e., sports measured in centimeters, grams, or seconds) are characterised by a strong emphasis on physical capabilities and relatively lower technical and tactical requirements (28). This sports category is conceptually consistent with the notion of “late specialisation”, as it contrasts with early specialisation (e.g., gymnastics). Empirical evidence supports this view, indicating that intensive training adaptations during adolescence are crucial for attaining long-term athletic success (28, 29).

Elite athletes in this cohort achieved success primarily in a limited number of sports, with many reaching that level through “sports transition”. While logistic regression identified sports transitioning as a predictor of elite attainment in this study, this should be interpreted as a context-specific association within the Fukuoka L-TID programme rather than definitive evidence of deliberate optimal matching. This finding aligns with the value of diverse sporting experiences in childhood as a foundation for later success. In this context, sports transitioning should be viewed as a context-specific association where accumulated experiences across multiple sports could be leveraged to support long-term development.

Most elite athletes in this study transitioned to late-specialisation sports such as athletics, cycling, and rowing. Moesch et al. (28) argued that late specialization is advantageous in cgs sports, where physical and mental maturity are critical. It is likely that these athletes optimised their potential by gaining broad experiences early by focusing on their main sport later. Importantly, the higher success rate observed in these sports may reflect structural advantages, such as lower national participation density or reduced selection barriers for senior representation, rather than the superiority of the programme's matching mechanisms alone.

Moreover, the concentration of elite athletes in certain sports suggests that these sports benefitted from robust regional development environments. As emphasised by Henriksen & Stambulova (30), a supportive social context including family, schools, clubs, and federations likely functioned as a comprehensive development environment for elite success. It can also be inferred that these sports maintained well-established cooperative relationship with their National Federations (NFs). As De Bosscher & De Rycke (31) reported, the effectiveness of system-level talent development programmes heavily depends on collaboration with national governing bodies. Such partnerships likely facilitated structured athlete development pathways that supported talented individuals reaching elite status. Taken together, these findings indicate that in the specific sports where athletes achieved elite status in the L-TID case study, their success was supported by three key factors: diverse sporting experiences during childhood, late specialisation, and strong collaboration between the regional development environments and the NFs.

Our study demonstrates a strong RAE among L-TID graduates at the Talent stage, but this effect appears to diminish among senior elite athletes (Table 7). Furthermore, RAE was not identified as a predictive factor in logistic regression analysis (Table 8). This pattern is consistent with previous findings suggesting that RAE varies across developmental stages (32, 33). The pronounced RAE pattern observed at the Talent stage supports the widely accepted view that, within a given age group, relatively older children tend to be more physically mature and fit, giving them a selection advantage (32–35). In contrast, the diminished RAE among senior elite athletes suggests that the phenomenon does not persist throughout long-term development, a finding corroborated by several international researchers. For example, Kelly et al. (36) found that in men's rugby union, early-born athletes were overrepresented in youth academies, but this effect disappeared at the professional and national levels. Similarly, Brustio et al. (37) observed that in athletics, RAE was evident in the U18 category but absent at the senior level, with relatively younger athletes more likely to successfully transition to the senior elite stage. However, it must be acknowledged that the small elite sample size (n = 31) limited statistical power of the analysis, meaning that the presence of a small-to-moderate RAE effect cannot be definitively rule out.

Furthermore, the persistence and direction of RAE patterns can vary by sport and even by position. Jones et al. (38) reported a traditional RAE among elite cricket batters and rugby backs, but a reverse trend among rugby forwards, where late-born athletes were overrepresented. No RAE was found for cricket pace bowlers. These findings suggest that physical attributes that confer early advantages may become less critical at the elite level, where technical skills, tactical understanding, and psychological resilience become more decisive (35). Moreover, Sasano et al. (19) reported that highly skilled athletes may overcome initial selection biases during their development. As Mann & van Ginneken (33) suggested, the transparent presentation of athletes' birth-month data during junior selection processes could help mitigate RAE-related biases. Taken together, the findings from the L-TID case study indicate that while RAE strongly influences initial selection at the Talent stage, its effect diminishes or disappears among senior elite athletes who progress through athlete development pathways. Consequently, while RAE did not emerge as a significant predictor among senior elite athletes in this study, this finding remains inconclusive due to the limited statistical power of the small elite sample. Therefore, RAE should not be definitively ruled out as a potential influence on long-term development.

The present study identified two consistent predictors of elite attainment from the Talent and Elite stages: sex (female) and sports transitioning (Table 8). Notably, being female showed a significant statistical association with elite status within this cohort. However, the exceptionally high ORs (e.g., 127.696 in 9th grade) and the wide 95% CIs for these estimates likely reflect statistical instability and uncertainty due to the small elite sample size and cohort imbalance. Therefore, these findings should be interpreted as programme-specific observations rather than generalized trends. Sports transitioning also maintained a significant and positive effect across all models, with high ORs observed in the upper elementary grades (e.g., 27.047 in 5th grade; 7.140 in 6th grade).

The strong association between female athletes and elite attainment within the L-TID programme (Table 8) is particularly significant when contrasted with well-documented challenges surrounding female sport engagement and retention in Japan. The decline in sport and physical activity participation among females becomes particularly evident during the transition between educational stages (25). For example, the time spent on physical activity outside compulsory physical education classes decreases significantly from upper elementary to junior high school. Consequently, the sport participation rate among females drops sharply in their 20s–40s (39). Data from national sport organizations also reveal that the gender disparity in participation rates, already present in youth categories, significantly widens in adulthood (40, 41). This cumulative decline represents a substantial talent loss in the female athlete talent pipeline during adolescence.

The reasons behind this female disengagement from sport participation are multifaceted, rooted in socio-cultural factors and systemic issues within the sporting environment. Previous study indicated that barriers such as aversion to sun exposure, discomfort from sweat or fatigue, and fear of negative social evaluation, or competition/ranking (42). In addition, limited understanding among coaches of female-specific developmental and physiological factors contribute to higher dropout rates (43, 44). Surveys consistently show that women report greater feelings of exercise deficiency than men across multiple age groups, highlighting a broader public health concern (45).

Therefore, the exceptionally high ORs observed for females (e.g., OR = 127.696 in 9th grade) are best interpreted as the result of a favorable confluence between the external environmental factors within the Japanese sporting context (i.e., the current status of female sport participation and retention.) and the programme's structural factors (e.g., talent selection concept, multi-sport strategy, and coach/guardian's competency, etc.). While the programme's structure is designed to offer equivalent opportunities to both sexes, this design appears to have mitigated some structural and socio-cultural barriers (e.g., coaching practices, societal expectations) that typically lead to high dropout rates among female athletes in Japan. Within the specific context of this programme, this association suggests it may be particularly beneficial for talented female athletes, enabling their continued participation and progression to elite status by addressing the gender-specific challenges prevalent in the Japanese sports environment.

The consistent and strong positive predictive relationship between sporting history and talent identification reinforces the programme's emphasis on non-early specialization (Table 8). This approach aligns with established Long-Term Athlete Development models advocating for multi-sport participation in early years to build a broad movement skill foundation and enhance physical literacy (11, 46). The exceptionally high ORs observed in upper elementary grades (e.g., OR = 27.047 in 5th grade) suggest that early exposure to diverse sports prior to specialisation is a critical foundation for developing high-level athletic potential. Such diversity enhances adaptability, reduces the risk of overuse injuries and burnout associated with early specialisation (47), and subsequently supports athletes' natural alignment with sports best suited to their matured physical and psychological profiles. The TID programme's capacity to identify late-emerging talent through sports transitioning, rather than favoring early performers, represents a key structural strength that maximises the potential of overall athlete pool.

This study has several limitations. First, the limited sample size of the elite athlete group (n = 31) resulted in wide 95% CIs for the key ORs, leading to residual uncertainty in the precision of these estimations. While the consistent direction and significance of the ORs across grades offer strong evidence, future studies with larger cohorts are necessary to enhance the precision of these results. Furthermore, the low number of athletes who successfully transitioned from the L-TID programme to senior elite representation, along with the fact that this study is based on a case study from a single region (prefecture), limits the generalizability of our findings (48, 49). However, the current findings are valuable for providing new perspectives to L-TID practitioners in comparable settings.

Second, although we focused on anthropometric and fitness characteristics, sports performance is also influenced by psychological skills, technical proficiency, and tactical awareness (50, 51). Thus, future research should adopt a more holistic, multidisciplinary approach than what currently exists (49, 52).

Third, identifying and developing talent among elementary and junior high school athletes remains inherently challenging task, as long-term success at the Talent stage is difficult to predict, raising questions about the cost-effectiveness of such programmes (53–56). However, within the context of Japanese sporting culture, educational and personal-development outcomes such as life skills, interpersonal skills, and social competence may justify these TID programmes beyond performance outcomes.

Furthermore, extrapolation of these findings to other geographical regions or TID systems requires verified application that explicitly considers differences in sport composition and institutional design. Future research should explore how cultural contexts and diverse of TID philosophies across nations shape the broader objectives and roles of these programmes. It is also important to examine how specific experiences within TID programmes influence the long-term performance trajectories of elite athletes.

Based on these findings, the following recommendations are proposed for the L-TID practitioners and broader policy makers:

Recommend support for female athletes and sports transitioning: Given their significant influence across all developmental stages, future strategies should prioritise structural support for female athlete retention and integrate initiatives that promote multi-sport experience and deliberate talent transfer/optimisation.