Talent development in childhood: Early specialization or sampling? From an either… or… question to a 2 × 2 × 3 question cuboid

Abstract

A central, yet still unresolved, question about optimal youth talent development asks whether children should specialize and train systematically in one sport—early specialization—or gain different playful experiences in several sports—early sampling. Based upon theoretical considerations, we problematize dichotomous discussions and offer a complex 2 × 2 × 3 question cuboid differentiating between two goals (performance in adulthood and positive youth development), two continuum-based dimensions (task-specificity and exercise mode), and three perspectives (nomothetic, group-specific, and idiographic). Accordingly, resolving the question about optimal youth talent development involves assembling answers derived from 12 different questions. Through our theoretical contribution, we identified several nomothetic principles offering stakeholders initial recommendations and orientations to estimate the appropriate need for high task-specificity and exercise mode in relation to each goal. We suggest adapting these recommendations according to group-specific characteristics, such as sport and age, and idiographic fine-tuning according to children's biopsychosocial characteristics.

Keywords

Developmental model of sport participation expertise multi-sport play positive youth development practice

Introduction

One premise of developmental science includes childhood experiences influencing what happens later in life.¹ It raises a central, yet still unresolved, question about optimal youth talent development: whether children should specialize and train systematically in one sport—early specialization—or gain different playful experiences in several sports—early sampling.^2,3 Each approach represents different answers to the question of optimal talent development in childhood—a different “story” we believe guides our choices and recommendations. Each story has several proponents and entails arguments emanating from two theoretical frameworks: the developmental model of sport participation (DMSP²) and the deliberate practice (DP³) framework (Table 1).

Table 1.

Two stories of talent development in childhood (early sampling and early specialization) and their origins, hypotheses, and proponents.

	Story
	Early sampling	Early specialization
Origin	Developmental model of sport participation (DMSP²)	Deliberate practice (DP) framework³
Hypotheses	1. Sustainability:⁴ with multi-sport training, children are less prone to injury, dropout, and burnout and more motivated long-term. 2. Multiple-sampling-and-functional-matching:⁴ with multi-sport training, every child finds the sport best suited for them. 3. Transfer-as-preparation-for-future-learning:⁴ the greatest possible variation in learning experiences creates a broad foundation that increases future learning capacity and adaptability.	1. The-law-of-practice: the more you practice specifically, the better you become. 2. Biological necessity: children who start DP early reap benefits missed by those who start later. 3. System-related necessity: children who do not start early will not have access to talent development programs, thus little chance of success.
Proponents	^2,4–12	^13–21

When people believe different stories, conflict results.²² For instance, proponents of early sampling blame the early specialization approach for jeopardizing positive youth development (PYD) through biopsychosocial health problems, such as injury,²³ burnout,²⁴ social problems,²⁵ and compromising long-term, joyful sport participation.²⁶ In reply, proponents of early specialization point out the lack of evidence for such health problems^27,28 and explain such findings with implementation issues, instead of content-related ones. For example, there might be no risk with early specialization per se, and adverse consequences could actually only result from wrongful training methods, implementation, and management.²⁹ In fact, biopsychosocial health problems might also arise as a potential consequence of the DMSP approach in later career stages: individuals who sampled in childhood have a shorter specialization period spanning from 12 to 18 years (in contrast to 0 to 18 for DP). This condensed timeframe may require them to engage in more demanding training, both in terms of volume and intensity, in order to catch up with those who started earlier. In turn, such endeavor to catch up might increase their risks of injury, burnout, and social isolation.

To sum up, one question captures the debate about early specialization or early sampling pathways: which story—which answer—is better for optimal talent development in childhood?³⁰ However, an increasing number of dissenting researchers doubt we can reach consensus (see e.g. for swimming,³¹ gymnastics,³² ice hockey,^33–35 basketball,³⁶ and soccer^37–39). In response, the present conceptual paper questions the dichotomous—either–or—nature of the proposed choices and introduces an analytical framework. This framework will show that each story provides necessary but insufficient information for theorizing optimal talent development in childhood. Building our analytical framework required restructuring three considerations from current understandings:

Two explicit goals, instead of an unclear mix of three implicit goals

Two continuum-based dimensions, not one dichotomous dimension

Nomothetic “laws,” group-specific “laws,” and idiographic fine-tuning rather than just nomothetic laws

Theoretical restructuring

Considering two explicit goals instead of an unclear mix of three implicit goals

The dichotomous debate between two stories tends to cover three goals³⁰ and implicitly expects one story to rule them all:

Performance—success maximization at peak performance age (in adulthood)

Personal development in the sense of PYD—self-esteem, social skills, and well-being

Participation—attrition versus long-term engagement

However, such expectations can result in conflicting findings and difficulties making informed decisions. Which story should we recommend if one goal is better achieved by the early specialization story, yet the other two goals by the early sampling story? In which order of importance should we rank the three goals? For instance, the DP framework clearly makes recommendations toward one explicit goal—performance—and disregards the other two goals. In contrast, DMSP includes all three goals in its reflections, yet seems to rank the latter two—PYD and participation—higher than performance.

Since DP and DMSP rank goals differently, we argue the problems they investigate are distinctive. Unsurprisingly, the answers they recommend for policymakers are different. Similarly, as different youth sport departments (e.g. elite versus non-elite), researchers, parents, or coaches have varying interests, they probably rank the three goals differently. Although there are plenty of goal-mixing recommendations about what might be best for the child overall,^40,41 we are not aware of any study providing clear recommendation for explicitly specified problem.

Our interest lies with stakeholders working in elite youth sport talent development. Their fundamental problem involves leading children through optimal support to international levels, such as earning Olympic medals, at ages of peak performance.⁴² Consequently, they prioritize¹ the maximizing performance goal, yet—undoubtedly—must consider PYD for ethical and pedagogical reasons aligned with recent, legitimate discussions.^43–45 In contrast, they likely allocate minor importance to the goal of lifelong sport participation (i.e. health promotion and non-elite sports issues for the general population).⁴² As such, in elite youth sport talent development, we suggest that only two goals really matter: performance and PYD.⁴⁵

Considering two continuum-based dimensions instead of one dichotomous dimension

From one to two dimensions

Four constructs—early specialization, DP, sampling, and play—usually describe training characteristics. Typically, they come in pairs.^46,47 For instance, Côté et al.³⁰ used “the term sampling to define an early environment in sport that included both deliberate play activities and involvement in several sports” (p. 579). Similarly, in their systematic review about “what defines early specialization,” Mosher et al.⁴⁸ noted that several authors “suggested it is the type of participation (i.e. deliberate practice) that is a key marker of early specialization” (p. 2). However, criticism emerged against such one-dimensional, “paired” conceptualization because it underestimates the complexity of training realities.⁴⁹ For instance, what if children perform only one sport (specialization), yet play that sport frequently, or, inversely, if they perform several sports (sampling), yet they practice deliberately in all of them? In short, such situations call for considering two dimensions instead of just one involving two questions: are children playing or do they practice deliberately and are children collecting experiences in one (specialization) or more sports (sampling)?^29,50,51

From dichotomies to continuums

Usually, the four constructs describing training characteristics are understood as (either–or) dichotomies: we speak about sampling versus specialization (cf. titles from^23,24) or practice versus play as if pure, clearly separate forms. However, boundaries are blurrier than previously thought; we suggest the presence of continuums (instead of dichotomies) and hybrid, in between forms (instead of a mirage of space between dichotomized constructs). Thus, sampling can be more or less “specialized” and practice more or less “playful.” Such continuum-based conceptualizations respond to Baker et al.'s⁵² recent call for rejecting “false dichotomies” (p. 6) to expand the discourse around talent development.

Specialization versus sampling. Accordingly, we advise viewing specialization and sampling as two poles of a continuum. Taking football as example, we believe the combination of football and futsal, football and other invasion games (e.g. basketball), or football and non-games sport (e.g. alpine skiing and artistic gymnastic) does not represent the same kind of sampling but different degrees of specialization.

Practice versus play. We offer the same advice for practice versus play. Instead of thinking of play and practice as dichotomous, we suggest acknowledging infinite nuances between them: children play football on the street with their friends² or practice with a playful attitude⁵³ or deliberately practice specific technical skills with their coaches.³

Toward a theoretical framework with two continuum-based dimensions

Aligned with such expansive reasoning, Sieghartsleitner et al.⁵¹ deserve credit for three main additions to the discourse. First, they structured the specialize–sample debate with two continuum-based dimensions. On the abscissa in Figure 1, their model considers the dimension “performance orientation”—from play to practice. On the ordinate, it displays the dimension “domain-specificity”—from sampling to specialization. Second, they illustrate that the most popular and scientific contributions to the debate often only address the two extreme poles—low versus high degree of expression in both axes—DMSP² versus DP framework.³ And third, they link a third path to success in adulthood in football⁵¹ and ice hockey³⁵: the path of specialized sampling. As depicted in Figure 1, this third path gathers within-sport experiences across the whole spectrum of the performance orientation continuum—play and practice.

Figure 1.

Original two-dimensional model of training approaches in childhood (Sieghartsleitner et al.⁵¹ p. 9). Source: Reprinted with permission from the authors and the publisher Frontiers.

However, fully following the model's two-dimensional continuum-based idea theoretically suggests not three, but infinite, possible paths to success. To fill undefined gaps in the model and provide more orientation, we modified it and expanded its terminology (Figure 2).

Figure 2.

Our modified two-dimensional model of training approaches in childhood.

Task-specificity continuum. Some degree of task-specificity possibly diverges from “specialized sampling” and (any) random sampling—instead corresponding to something in between—suggesting the label “task-related sampling” (Figure 2). Task-related sampling refers to partially diversified training, with several sports within a certain group of sports with some similarities with the targeted sport. In football, basketball, or tennis, it possibly corresponds with ball-related sampling, whereas in artistic gymnastics or figure skating possibly acrobatics-related sampling.

Exercise mode continuum. Similarly, some degree of exercise mode possibly diverges from “play” and “practice”—again corresponding somewhere in between—suggesting the label “playful practice”^49,54 (Figure 2). On the one hand, playful practice means learners experience playfulness even when training is more structured, less fun-oriented, and less self-regulated than “play.” On the other hand, learners feel they are practicing to improve, yet the training is more fun-oriented, less structured, and less coach-led and characterized by fewer explicit instructions and feedback compared with the traditional construct of “practice.”

Considering nomothetic laws, group-specific laws, and idiographic fine-tuning instead of only nomothetic laws

Waldron et al.⁴¹ critically reviewed and summarized different position statements from several major medical organizations regarding early specialization. For instance, the American Medical Society for Sports Medicine (AMSSM) concluded “early sport specialisation may not lead to long-term success in sports, and may increase risk for overuse injury and burnout”⁴⁰ (p. 12) and the American Academy of Pediatrics posited “young athletes who specialize too soon are at risk of physical, emotional, and social problems”²⁵ (p. 5). Similarly, when asked “what makes a champion?,” Güllich et al.⁴ responded “early multidisciplinary practice, not early specialization” (p. 6). These position statements are nomothetic—unspecific to situations or people, yet concerning everyone—supposing all children and all sports function the same and encapsulating one-size-fits-all expectations regarding PYD and performance goals. As such, like most contributions to the sample-or-specialize discussion (see^{26,41,55–57}), they reduce a complex debate into a simple, tendentious dichotomy of “specialization is bad, sampling is good” for everyone.⁵⁸ However, nomothetic perspectives are insufficient for understanding an individual's development.⁵⁹ In the developmental sciences, three kinds of “laws” (or perspectives)—nomothetic, group-specific, and idiographic—are established for understanding human development. They trace back to Kluckhohn and Murray's⁶⁰ (1948) insight that “all people are like all other people, all people are like some other people, and each person is like no other person” (cited by Lerner,⁶¹ p. 7).

Nomothetic perspective is an appropriate starting point for generating general guidelines. However, since each sport has unique training and competition requirement profiles and different cultures⁶² and each athlete has unique characteristics, such as genotypes, environmental characteristics, and phenotypes,⁶³ seeking only an absolute, nomothetic winner story is designed to fail, such as contending training A is better than training B for all people.

Ideally, group-specific laws—with goals, sports, and ages considered and defined—complement nomothetic laws. For example, training A is better than training B for group C. Initial group-specific analytical attempts exist, yet remain rare and incomplete. For instance, researchers considered training content in relation to sport-specificity and compared different sport category types, yet disregarded age-specificity.^4,64 Conversely, others considered age-specificity in theoretical models, such as the Youth Physical Development (YPD) model (see^44,65–67), yet omitted sport-dependent adjustment recommendations. In brief, we need more precise developmental theoretical guidelines combining sport- and age-specificity.

Finally, while nomothetic and group-specific recommendations provide a big picture, idiographic fine-tuning—adjusting to individual biopsychosocial characteristics—accommodates details. The International Olympic Committee (IOC) consensus⁶⁸ stresses “youth athlete development is contingent on an individually unique and constantly changing base of normal physical growth, biological maturation and behavioral development, and therefore it must be considered individually” (p. 8). However, how to apply idiographic fine-tuning remains unknown.

The 2 × 2 × 3 questions cuboid

We started with a two-sided coin toss to answer only one question: is the “sampling and playing” or “specializing and deliberate practice”, story better? The question reflects the traditional goal-mixing, one-dimensional, dichotomized, nomothetic, either–or thinking from current talent development discourse. However, our considerations demonstrate a substantial “unit of analysis” change. It seems we actually deal with a complex 2 × 2 × 3 question cuboid² (Figure 3) made of two explicit main goals for talent development, two continuum-based dimensions, and three perspectives.

Figure 3.

The 2 × 2 × 3 question cuboid of optimal training in childhood within the context of talent development (PYD: positive youth development).

Taken together, 12 questions emerge across nomothetic, group-specific, and idiographic perspectives.

Nomothetic perspective

What degree of task-specificity leads to maximum success at peak performance age?

What degree of exercise mode leads to maximum success at peak performance age?

What degree of task-specificity leads to PYD?

What degree of exercise mode leads to PYD?

Group-specific perspective

What degree of task-specificity leads to maximum success at peak performance age given the “type of sport” and “age” group-specific characteristics?

What degree of exercise mode leads to maximum success at peak performance age given the “type of sport” and “age” group-specific characteristics?

What degree of task-specificity leads to PYD given the “type of sport” and “age” group-specific characteristics?

What degree of exercise mode leads to PYD given the “type of sport” and “age” group-specific characteristics?

Idiographic perspective

What degree of task-specificity leads to maximum success at peak performance age given the group-specific characteristics and the child's biopsychosocial situation?

What degree of exercise mode leads to maximum success at peak performance age given the group-specific characteristics and the child's biopsychosocial situation?

What degree of task-specificity leads to PYD given the group-specific characteristics and the child's biopsychosocial situation?

What degree of exercise mode leads to PYD given the group-specific characteristics and the child's biopsychosocial situation?

When determining an individual's optimal training, we must assemble all answers from the 12 questions. Next, we analyze each perspective to uncover such answers.

Nomothetic perspective

Nomothetic laws are interindividual commonalities generalized for all humanity⁶⁹ (for developmental sciences, see Lerner and Lerner⁶³). From our standpoint, we present nomothetic principles most relevant—without claiming completeness—to answer questions 1 to 4. The principles serve orienting purposes to understand what circumstances alter task-specificity and exercise mode.

Goal 1: Performance

For the performance goal, we identified six principles from multidisciplinary literature (Table 2).

Table 2.

Nomothetic principles to define the degree of task-specificity and exercise mode for the performance goal.

Nomothetic principle	Field of study	Recommendations
Orthogenetic	Developmental psychology	The older/more experienced the child, the higher the task-specificity and exercise mode.
Plasticity	Motor development, biology	The higher the plasticity in an early developmental phase (compared to others) of motor learning, the higher the need for an earlier increase in task-specificity.
Peak performance age	Biology, sociology	The earlier the age range of peak performance, the earlier the increases in task-specificity and exercise mode.
Supply–demand	Sociology	The more demand and the less supply for a place in a talent development program, the higher the task-specificity and exercise mode.
Transfer	Motor learning, physiology, and psychology	The more transfer-pessimistic, the higher the need for higher task-specificity for functional sampling.
Technical requirement and condition variability	Motor learning	The higher the technical requirement, the higher the task-specificity and exercise mode. The more standardized the condition, the higher the task-specificity and exercise mode.

The orthogenetic principle

The orthogenetic principle applies to any variable regarded as developing, such as training.⁷⁰ Formulated over 60 years ago by Werner,⁷¹ it stipulates “whenever development occurs, it involves changes from globality to differentiation”⁶³ (p. 65). In alignment, YPD prescribes changes from globality to differentiation on both the task-specificity—from global fundamental motor skills to more differentiated sport-specific skills—and exercise mode continuums, from unstructured to structured approach, as a function of age. The older or more experienced the child, the higher the task-specificity and exercise mode.^66,67

The plasticity principle

Humans can change—they are plastic⁷²—and must change to reach certain task levels. Researchers analyzing human plasticity investigate questions, such as how do specific experiences modify our brain circuits; does the timing of experiences—too early or late in life—matter for ultimate attainment; and do critical or sensitive period exist where plasticity heightens? Different research paradigms—the deprivation paradigm (e.g. feral children⁷³) and the impoverished and enriched environment paradigm—shed light on how we change and develop with no, low-, or high-quality environmental input at given developmental times.⁷⁴ For instance, can we walk or talk “normally” as adults if we are only exposed to animal habits or confined in a small room deprived of human contact until a certain age,⁷³ can we reach language proficiency in adulthood with little or no exposure to specific language training until a certain age,⁷⁵ and can we reach musical proficiency, such as absolute pitch, with little or no exposure to musical training until a certain age?⁷⁶ Similarly, sport science asks whether we can reach sport or motor proficiency with little or no exposure to task-specific and performance-oriented training until a certain age. On some levels, the aformentioned question capture the essence of the specialize–sample debate.

Regarding plasticity of motor skills, the sensitive period hypothesis suggests the central nervous system matures at an accelerated rate—implying heightened neural plasticity—during childhood. Lloyd et al.⁷⁷ described “a non-linear decrease in the volume of gray matter in the brain with age, especially after the onset of puberty as the process of synaptic pruning takes place, thus making the ability to learn new motor skills more challenging as children become older” (p. 107). If the sensitive period hypothesis is true—which does not seem to be the case for sport-related movement acquisition so far—^78,79 an early increase in task-specificity may be neurologically necessary for some sports. In other words, starting learning too late is a risk, especially if the goal is an Olympic medal. Such risks are not isolated cases in the fields of animal and human development. For instance, “a number of sensitive periods seem to end as animals approach sexual maturity for example, heightened plasticity in the sound localization pathway in barn owls, song learning in some songbirds, and certain aspects of language learning in humans decline as juveniles approach adulthood”⁸⁰ (p. 1419). Until proven otherwise, if the fields of language⁸¹ and musical learning⁷⁶ are somewhat affected by such a phenomenon, why should motor learning be an exception? Thus, the higher the plasticity in an early developmental phase (compared with others), the higher the need for an earlier increase in task-specificity.

Interestingly, in current neurosciences discourse, Anderson and Mayo⁸² noted, “the question shifted from whether sensitive periods exist to what process opens them, keeps them open, closes them, and allows them to reopen” (p. 224). As such, some “windows” may only open later in life or remain widely open lifelong, reducing the necessity of high task-specificity in early childhood. For instance, with regard to the plasticity of functional capacities, such as endurance,^83,84 the trigger hypothesis⁸⁵ claims plasticity is reduced among children compared with adults. If true—depending on the authors, we are either close⁸³ or far from it⁸⁶—an early increase in task-specificity is possibly physiologically pointless in certain sports; starting too early results in no gain. In alignment, the YPD model recognizes specific training for certain functional capacities can occur after childhood.⁶⁶ Thus, the lower the plasticity in an early developmental phase (compared with others), the later the need for an increase in task-specificity.

The peak performance age principle

The question of when to start task-specific and performance-oriented training depends on the age of peak performance minus the years needed to build corresponding expertise. If two sports demand an equal amount of training years to attain expertise, it can be inferred that the sport with the lower peak performance age would necessitate an earlier starting age. Thus, the earlier the age range of peak performance, the earlier the increases in task-specificity and exercise mode.⁵⁷

The supply–demand principle

Generally, the lower the availability of an object and the higher the demand, the higher the price to pay—a principle that does not apply differently when the object is a place in a talent development program. Since performing well in the short-term is crucial for selection, the fewer places offered within a system and the higher the number of applicants—from sport popularity or selection pressure—the more required the task-specificity and exercise mode.^35,87

The transfer principle

Motor learning is always based on previous experiences and thus, to some extent, on transfer effects.⁸⁸ The two extremes (DMSP versus DP) differ in their position on the continuum of task-specificity (low versus high) because of their different understandings of transfer—the former approach seems highly transfer-optimistic,^4,26 while the latter seems rather transfer-pessimistic.^3,20 A transfer-optimistic approach assumes “the benefit of other-sports practice is not moderated by the degree of relatedness of the other sports with one's main sport”⁴ (p. 17). Presupposing every (random) sporting experience counts and helps future learning capacity (and better career outcomes), it follows children should sample as broadly as they can during childhood. A transfer-pessimistic approach refers to Henry's specificity hypothesis⁸⁹; it suggests transfer effects are so small they can be neglected.⁹⁰ Such a hypothesis implies children should train in highly specialized manners for later success.

Since recent literature reviews give no clear-cut answers prioritizing either transfer-optimistic or transfer-pessimistic approaches,^91,92 we now speculate on a range of transfer opportunities using the century-old, yet still well-recognized, law of identical elements.⁹³ The law of identical elements considers each sports-related movement metaphorically as a kind of a building constructed from fundamental elements—also called modules.^94–97 The law of identical elements expects transfer if the same elements are found and trained in two buildings or sports-related movements, such as serving in volleyball and tennis. If not the case, no transfer occurs, such as no overlap from the modular architecture of road cycling and javelin throwing. At its core, the law challenges the idea of every movement experience as useful by seeing “functional sampling” as the only kind of sampling to facilitate the performance goal, such as sport with the degree of congruence with sporting tasks in the main sport or “donor sports.”⁹⁸

Since physiological capabilities, such as the “aerobic capacity” element, seem trainable more unspecifically in many sports (e.g. cross-country skiing, road cycling, track and field, soccer, basketball, and tennis),⁹⁹ their opportunities for functional sampling are possibly wider, suggesting endurance-based sports more transfer-optimistic. Inversely, technical skills, such as the “serving in tennis” element, are likely trained in more task-specific situations,^88,89 implying more transfer pessimism, suggesting sports with high technical requirements need higher task-specificity in order for sampling to be functional, that is, at least task-related or specialized sampling.⁹⁸ Thus, the more transfer-pessimistic, the higher the need for higher task-specificity.

The technical requirement and condition variability principle

Just like for language learning, sport requires play and practice, so individuals who only learn by playing never fully master specific intricacies, such as sport-specific movement execution. In contrast, individuals who only practice specific movements, such as only 13-m goal kicks in football, encounter difficulties activating and applying their knowledge in diverse game contexts.⁸⁸ However, the importance placed on play or practice varies depending on specific aspects, such as the technical requirements specific to each sport, which can range from low to high, and the variability of conditions in each sport, which can range from standardized to variable.

It seems plausible to assume that the higher the technical requirements of a sport, the more required the practice. Contrastingly, a stronger focus on play may fit more variable conditions.⁸⁸ Thus, if a sport possesses a high degree of expression for only one of two aspects, a particular focus on play or practice possibly dominates. For instance, artistic gymnastics is characterized by high technical requirements under standardized conditions (low variability),¹⁰⁰ suggesting a focus on practice. Conversely, alpine skiing might be characterized by relatively lower technical requirements, but it takes place under constantly changing conditions (high variability), suggesting a greater focus on play compared to aristic gymnastics.¹⁰¹ If a sport possesses a high degree of expression for two aspects, a focus remains undetermined (e.g. ice hockey³⁵ or football⁵¹), suggesting specialized sampling as depicted in Figure 1. Finally, if a sport shows low expression for both factors (e.g. bobsleigh), no focus is necessary. In this case, based on diversity principle (see below), we suggest play rather than practicing deliberately.

Goal 2: PYD

Regarding the goal of PYD, we identified two principles from the literature; we named them diversity principle and implementation principle. The former suggests what degree of task-specificity and exercise mode is preferable for PYD. If implemented, the latter suggests how each theoretically possible degree of task-specificity and exercise mode facilitate or hinder PYD.

The diversity principle

In Baker et al.'s⁵⁸ foundational paper, they reported “since 2017, there have been three systematic reviews and 10 narrative reviews/editorials about the negative implications of specialization in sport” (p. 179). So, the scientific community seems to have converging opinions about what is better for children's biopsychosocial health. The lower the exercise mode and task-specificity, the more diverse the training approach and the lower the risk of jeopardizing the goal of PYD.⁴⁰ Simply put, diversity over monotony is preferred.

On the task-specificity continuum, when moving from bottom (low) to top (high), the range of experiences becomes narrower and thus less diverse and more prone to monotony. More specifically, the range of opportunities for an open future and diversified athletic identity becomes narrower,¹⁰² risk for overload injury increases from lack of biomechanical diversity,²³ and risk of burnout increases from lack of psychological diversity.²⁴ Therefore, as task-specificity increases, the risks of neglecting important aspects of PYD also increase. On the exercise mode continuum, practice is less diverse than play; it is more serious, coach-led, repetitive, goal-directed, and intensive and, thus, the kind of training where children are likely stressed, pressured, criticized, or deprived of autonomous choice¹⁰³—in other words, possibly negatively impacting PYD.^30,104 Such reasoning increases awareness of valid arguments regarding probabilities of negative or positive consequences as functions of early sport specialization, sampling, play, and practice. However, Baker et al.⁵⁸ warn the scientific community by asking a ground-breaking question: “is it too early to condemn early sport specialization?” (p. 179). In response, we contend it is premature because of the implementation principle.

The implementation principle

The labels “early specialization,” “sampling,” “practice,” and “play” have no fixed implementation. Under all degrees of task-specificity and exercise mode, the training can be delivered in ways that are better (or worse) than others to promote physical and psychosocial health.⁵⁸

Risks of negative physical consequences surely differs if coaches treat children as “miniature adults” or as children,¹⁰⁵ if they plan training based on short- or long-term success expectations, if they integrate aspects related to injury prevention programs or not,⁵⁶ and if they adapt training load according to experience or maturity or not.^56,106–110

Risks of negative psychosocial consequences also surely differ according to psychosocial context. According to Vallerand and Losiers's motivational sequence,¹¹¹ the social microsystem involved in training and evaluating the performance acts on basic psychological needs for competence, autonomy, and relatedness,¹¹² which then influences one's intrinsic motivation and leads to different consequences, such as well-being, dropout, and burnout. Accordingly, it definitely matters whether “unsupervised play” takes place with same age peers, younger or older children, or with or without bullies. Similarly, different coaching styles during coach-led deliberate practice, such as controlling or autonomy-supportive;¹¹³ different motivational climates, such as ego- or task-oriented;^114,115 and different pedagogical approaches, such as with or without self-concept promoting teaching principles,^116,117 represent different contexts, which impact children's basic psychological needs, motivations, and thus PYD differently.¹¹⁸

Thus, although some correlation between a specific label and risk for PYD is possible, the correlation is likely weak. In fact, correlation is likely spurious, resulting from the fact that unfavorable implementations occur more frequently—yet not necessarily—in training contexts characterized by both high degree of exercise mode and task-specificity. So, blaming a given degree of task-specificity and exercise mode by defining it with a good or bad fixed implementation is inappropriate. Consequently, we suggest researchers reflect upon what kinds of early specialization are “healthier,” sampling “unhealthier,” practice “healthier,” and play “unhealthier” than others. When considering such possible nuances, we agree with Baker et al.⁵⁸: it remains unclear whether the risk of early specialization and the protective value of early sampling are as high as usually claimed. Therefore, as Lerner et al.¹¹⁹ stated, “scholars, practitioners, and policy makers may always remain optimistic about finding some intervention to reduce problem behaviours” (p. 12).

Group-specific perspective

In the previous section, we highlighted nomothetic principles steering the degree of expression of each dimension either downward or upward. However, in view of the goal of performance, different sports and ages possibly possess different properties regarding orthogenetic development, plasticity-related situations, peak performance ages, supply–demand constellations, transfer opportunities, reliance on technical requirements, and condition variability. For instance, peak performance ages possibly differ between cgs and artistic composition sports, and plasticity-related situations likely also differ for children aged 3 or 11 years. In view of PYD-goal, distinctive sport and age differences regarding inherent diversity potential and implementing training content exist. For instance, ranges of within-sport opportunities for diversity are probably narrower for 100-m sprint compared with ice hockey and narrower for children aged 3 or 11 years. Similarly, regarding typical training implementation, various factors such as age (e.g. age-related biopsychosocial stress resistance) and cultural sport differences play a role. For example, freestyle skiing may appear to be more autonomy-supportive, while artistic gymnastics and figure skating may have a more traditional and controlling atmosphere.^120,121 Thus, it makes sense to look for a group-specific theoretical guideline—a guideline considering sport- and age-specificity. To our knowledge, no such guideline exists. Therefore, as texture to complement our theoretical contribution, we reached out to sport federations to seek their perspective on this issue: where do they position themselves in Figure 2 across various age groups? This question relates to questions 5 and 6 mentioned in the cuboid—what degrees of task-specificity and exercise mode lead to maximum success at peak performance age given the group-specific characteristics, “type of sport,” and “age”? Additionally, we investigated how such degrees are possibly problematic regarding PYD (questions 7 and 8). Please note that our interest lies primarily in the positions of sport federations, not in the voices of individual participants. Thus, we see our contribution as theoretical enriched with empirical supplements, not an empirical contribution.

Perspective of sport federations

Participants: between February and April 2022, we interviewed chairs of youth elite sports from 11 sports federations in Switzerland. We aimed to cover different groups of sports occupying central roles in the debate^4,64—cgs sports, games sports, and artistic composition sports (Table 3). As leaders within their respective sports federations, our interviewees hold the responsibility of shaping talent development concepts and embody the perspective of their federation.

Table 3.
Sports federation experts interviewed sport categories.

Cgs sports Games sports Artistic composition sports

Rowing, alpine skiing, mountain biking, road cycling, and track and field Football, ice hockey, floorball, and tennis Figure skating and freestyle skiing

Data collection and analysis: Each interview lasted ∼90 min. The interviews were conducted, analyzed, and critically discussed with explicit reference to Sieghartsleitner et al.'s⁵¹ (2018) model (Figure 1) as part of a post-graduate course that we supervised on the “sampling versus early specialization” topic. The post-graduate course included nine students, spanned 12 weeks from February to June 2022, with weekly meetings of four discussion hours each. In June 2022, we presented our results on sport- and age-specific positions within Figure 2 at a national symposium jointly organized by Swiss Olympic and the University of Bern. The symposium brought together 70 key stakeholders from elite sport in Switzerland, including around 40 chairs of youth elite sports from different sports federations. After the results presentation, the symposium participants were divided into three workshop groups corresponding to their area of expertise: cgs, games, and artistic composition sports (as shown in Table 3). These workshop groups allowed for critical expert discussions (45 min), enabling us to triangulate diverse perspectives and seek consensus on the findings. The original positions remained largely unchanged after the workshops, indicating validation by the community.

Member check: We presented our results to our 11 interviewees three times to ensure communicative validation and trustworthiness of the findings.^122,123 Firstly, we contacted the interviewees by telephone two weeks before the symposium in May 2022 to address any uncertainties in interpretation. Secondly, during the expert workshops in June 2022, the interviewees had the opportunity to share their expertise and make any necessary modifications to the results after discussing with other chairs of youth development. Lastly, in September 2022, we sent the results to the interviewees for their final consent and validation. All interviewees provided written informed consent for their participation.

Overview

Figure 4 displays the positions specific to each sport and age group. The positions are shown in three separate graphs, one for each sport group. The colors in the graphs represent the time axis, with darker colors indicating older children. Regarding performance goal, almost all specifications between DP and DMSP appear to be success-promoting (Figure 4), yet neither DP nor DMSP is applied in pure form from starting age (at least) until the end of childhood. There is a vacuum in the bottom right part of the model, suggesting high exercise mode with low task-specificity as an unfavorable or nonsensical strategy in all sports and ages. Regarding the PYD-goal, our interviewees reported biopsychosocial problems as more frequent in sports and ages with higher degrees of task-specificity and exercise mode compared with lower ones. They also indicated a lack of age- and sport-specific information regarding kinds of training implementation, which possibly helps mitigate or eliminate such problems.

Figure 4.
Group-specific perspective on the question of optimal degree of task-specificity and exercise mode according to age and sport from the point of view of the heads of national youth development of selected Swiss sport federations.

Cgs sports

With the exception of alpine skiing, cgs sports possess a slower orthogenetic tempo: they remain at lower levels of task-specificity and exercise mode for an extended period of time. The lower the technical–coordinative demands of the sport considered, the more pronounced the trend seems—for example, the lower position for road cycling compared with mountain cycling. Since cgs sports are often primarily determined by functional capacities, their (relatively lower) age-specific positions on the task-specificity continuum compared with the other sport groups are possibly explained by (supposedly) lower plasticity-related properties in early childhood and/or more transfer-optimistic view and/or more worries to guarantee PYD from inherent lower diversity potential. Relatively lower age-specific positions of cgs sports on the exercise mode continuum are possibly explained by their low expression on both factors of the technical requirements and condition variability principle—meaning no focus between play and practice is necessary. For this reason and considering the diversity principle, children should preferably play.

Game and artistic composition sports

For both game sports and artistic composition sports, faster orthogenetic tempo and higher positions in both dimensions at earlier ages were considered necessary. More specifically, considering factors such as high technical requirements, plasticity potential, peak performance age, and supply–demand ratio, experts in game and artistic composition sports recommended prioritizing experiences including transferable elements in early training stages, such as ball-related and acrobatic-related experiences, respectively. Such a “higher” starting position on the continuum (task-related sampling on Figure 2) is then rapidly followed with a move toward specialized sampling. Accordingly, experts in game sports, artistic composition sports, and alpine skiing tend to lean toward a transfer-pessimistic viewpoint, and this pessimism seems to increase as children mature.

The relatively high age-specific position of artistic composition sports on the exercise mode continuum can be attributed to their high technical requirements and standardized condition variability. Small differences between figure skating and freestyle skiing are possibly attributed to differences in condition variability, with freestyle skiing being less standardized. In contrast, game sports score high on technical requirement and condition variability factors from their complex and unpredictable nature. Consequently, interviewees positioned game sports across the entire range of the exercise mode continuum (implying undetermined focus).

Idiographic perspective

So far, we based the group-specific recipe—for pragmatic reasons—on a homogeneity assumption: Figure 4 displays the success paths of a hypothetical, interchangeable individual with a given age in a given sport. However, individuals are not interchangeable members of a single age- or group-specific class—they are not structurally and functionally equivalent machines devoid of individuality.¹²⁴ On the contrary, each person possesses different genetic,¹²⁵ biological,¹²⁶ psychological,¹²⁷ and sociological¹²⁸ profiles and thus different probabilities for experiencing negative or positive consequences if they find themselves in specialized, sampling, practice- or play-oriented settings during childhood. As a result, idiographic adjustments of group-specific perspective seem necessary. To our knowledge, only Hohmann et al.¹²⁹ discussed the individually fine-tuned relationship between specialization and diversification in youth training. They highlighted the dual dependence of this relationship, considering both the sport's versatility and the individual's athletic versatility. Due to the limited guidance available for researchers and practitioners in compiling information into individualized programs of optimal training for a specific individual, we discuss some issues next.

In principle, to achieve success at peak performance age, increases of task-specificity and exercise mode occur as early as necessary. However, risks associated with delayed task-specificity and exercise mode may be—at least to some extent—compensated (or aggravated) by other factors. For instance, children differ in their plasticity for genetic,¹³⁰ biological,¹³¹ or experience-related reasons.^78,132 Thus, some can start later or train differently to reach the same future performance levels. Furthermore, training content during childhood is not the only predictor of future success. Other dimensions of the “talent” phenomenon increase or decrease chances for future professional careers,^133,134 such as psychological characteristics^135,136 or family support.^137,138

Similarly, and in principle, to promote PYD, increases of task-specificity and exercise mode training occur as late as possible. However, risks associated with high task-specificity and exercise mode may be—at least to some extent—compensated (or aggravated) by other factors, such as functional and dysfunctional factors for talent development.¹³⁹ For instance, “athletes’ entourages […] matter in a variety of ways in athletes’ socialization toward refraining from risking their health in pursuit of greater achievement and outstanding performance” (p. 1).¹⁴⁰ Children specializing in one sport with parents with a background in pedagogy and coaches with jobs independent of short-term success possibly possess lower risk for biopsychosocial problems than children sampling different sports with parents and coaches pushing for short-term success. Furthermore, despite early specialization criticism as “too narrow”^26,30 and sampling praised for its breadth,¹¹ not all children react identically to “narrower” developmental opportunities or react negatively. For instance, a minority of children appears to know their preferences early on.¹⁴¹ Such children do not feel emotionally disturbed if they specialize instead of being “forced to” experience a wide range of activities.¹⁴² In fact, a narrow focus on their passion possibly satisfies their basic needs for autonomy and increases their DP motivation.^143,144 Similarly, if children with strong perfectionist tendencies diversify training too much, they perhaps become good at many sports but not very good at any of them, which possibly jeopardizes basic needs for competence and leads to negative emotions, such as frustration.¹¹¹ Such scenarios align with the IOC consensus statement, which states “Appropriate diversity and variability of athletic exposure within a single sport […] can be acceptable and healthy, so long as the youth athlete is enjoying and benefitting fully from the experience” (p. 8).⁶⁸ It follows some children need more play or more sampling than others to experience their sporting career as meaningful and motivating. Accordingly, the challenge is to find what specific training approach in what specific context at what specific times in the life span affects what specific outcomes for what specific individuals.¹⁴⁵

Conclusion

Our conceptual work followed two steps. First, the starting point began with a popular question: should children specialize in one sport and train systematically in it—early specialization—rather than gain different playful experiences in several sports—early sampling? So far, researchers disagree on the best answer; the disagreement mainly emanated from one-dimensional, goal-mixing, either–or dichotomic, one-size-fits-all thinking. Second, after elaborating about the need for a new, non-dogmatic approach—a two-dimensional, goal-oriented, non-dichotomous, continuum-based, multi-perspectivist view—we introduced and discussed the 2×2×3 question cuboid. Our analysis suggests three recommendations for future research related to goal-oriented thinking, non-dichotomous and two-dimensional thinking, and nomothetic, group-specific, and idiographic thinking.

Goal-oriented thinking or ranking different goals in different orders of importance means dealing with different problems. Since different problems require different solutions, future studies should state explicitly what goal interests them and what kind of problem they investigate precisely. In talent development, two goals are deemed relevant: performance and PYD.

Non-dichotomous and two-dimensional thinking responds to a recent call from Baker et al.⁵² for distancing from the “focus on false dichotomies” (p. 6) and needing to openly and critically challenge existing approaches” (p. 7). We addressed the need by strengthening the idea of two dimensions (task-specificity and exercise mode), not one, and the idea of continuums (random sampling, task-related sampling, specialized sampling, specialization; play, playful practice, practice), not pure dichotomies. We suggest future studies investigate how to objectively define each continuum position.

Nomothetic, group-specific, and idiographic thinking highlighted 12 questions in the debate. From a nomothetic perspective, six performance-oriented (orthogenetic, plasticity, peak performance age, supply–demand, transfer, and technical requirement and condition variability) and two PYD-oriented principles (diversity and implementation) guide understandings about what is generally better for all. Nomothetic principles need to be re-evaluated according to group-specific characteristic—such as answers to questions like what is best in a given sport at a given age—and according to idiographic characteristics, such as what is best for a specific individual.

We recommend future studies investigate our conceptual analysis and address the lack of research in several areas of the 2 × 2 × 3 question cuboid, such as developing the body of knowledge about the three perspectives, two dimensions, and two goals, validating our proposal of sport- and age-specific localization within our adapted model and extending it to other sports, and considering other group-specific aspects modulating such localization. For example, since supply–demand ratio possibly differs between same-aged boys and girls in some sports such as football,¹⁴⁶ add sex-specific aspects. Similarly, since sport characteristics, such as technical requirements, peak performance ages, or supply–demand characteristics, likely change over time from technological innovations or political decisions, consider cohort-specific aspects. Future studies might also consider creating a roadmap for idiographic fine-tuning,¹²⁹ for instance, with the help of a person-oriented approach.¹⁴⁷ Such methodological approach helps identify a type of person—with particular biopsychosocial and training characteristics—as more likely to develop on low-, moderate-, or high-risk paths for biopsychosocial health problems and/or (non-)achievement of performance-related goals.¹⁴⁸

Finally, we suspect a 13th question remains—one we purposely unattended, yet should be addressed in the future. Are goals one (performance) and two (PYD) always compatible or perhaps somewhat limited by a trade-off? In other words, does maximizing one goal only happen at the expense of another? If divergent answers emerge, thinking about goal prioritizing and sequencing is essential: if we seek international success, what costs are we ready to let children pay for⁴¹? If risking PYD appears necessary in some sports to maximize success probabilities, yet societally, medically, and ethically unacceptable, should our political system promote such a sport at all?

Cgs sports	Games sports	Artistic composition sports
Rowing, alpine skiing, mountain biking, road cycling, and track and field	Football, ice hockey, floorball, and tennis	Figure skating and freestyle skiing

Footnotes

Acknowledgements

The authors thank (a) Swiss Olympic for their support organizing the symposium; (b) interviewees for their expertise and their time; (c) participants in the Master of Science seminar (Valentin Berra, Manuel Burger, Jasmin Hermann, Julia Hernandez, Nina Kaczmarek, David Kurz, Dario Querciagrossa, Yannik Schürch, and Jonas Siegrist) for their input and cooperation in the empirical illustration; (d) Merlin Örencik, Michael Schmid, and Ernst-Joachim Hossner for their helpful comments on an earlier draft of the manuscript; and (e) Kristin Marie Bivens for her editing work and guidance on our manuscript.

Author contributions

All authors substantially, directly, and intellectually contributed to the work and approved it before publication.

Declaration of conflicting interests

The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

ORCID iD

Bryan Charbonnet

Notes

References

1.
Lerner RM (ed). Individuals as producers of their own development: the dynamics of person-context coactions. New York: Routledge, 2021.

2.
Côté J Baker J Abernethy B . Practice and play in the development of sport expertise. In: Tenenbaum G Eklund RC (eds) Handbook of sport psychology. Hoboken: John Wiley & Sons, 2007, pp.184–202.

3.
Ericsson KA Krampe RT Tesch-Römer C . The role of deliberate practice in the acquisition of expert performance. Psychol Rev 1993; 100: 363–406.

4.
Güllich A Macnamara BN Hambrick DZ . What makes a champion? Early multidisciplinary practice, not early specialization, predicts world-class performance. Perspect Psychol Sci 2021; 17: 1745691620974772.

5.
Baker J Côté J Deakin JM . Expertise in ultra-endurance triathletes early sport involvement, training structure, and the theory of deliberate practice. J Appl Sport Psychol 2005; 17: 64–78.

6.
Barreiros A Côté J Fonseca AM . From early to adult sport success: analysing athletes’ progression in national squads. Eur J Sport Sci 2014; 14: S178–S182.

7.
Bridge MW Toms MR . The specialising or sampling debate: a retrospective analysis of adolescent sports participation in the UK. J Sports Sci 2013; 31: 87–96.

8.
Güllich A . Many roads lead to Rome–developmental paths to Olympic gold in men’s field hockey. Eur J Sport Sci 2014; 14: 763–771.

9.
Güllich A . International medallists’ and non-medallists’ developmental sport activities - a matched-pairs analysis. J Sports Sci 2017; 35: 2281–2288.

10.
Soberlak P Côté J . The developmental activities of elite ice hockey players. J Appl Sport Psychol 2003; 15: 41–49.

11.
Côté J Vierimaa M . The developmental model of sport participation: 15 years after its first conceptualization. Sci Sports 2014; 29: S63–S69.

12.
Moesch K Elbe A-M Hauge M-LT , et al. Late specialization: the key to success in centimeters, grams, or seconds (cgs) sports. Scand J Med Sci Sports 2011; 21: e282–e290.

13.
Helsen WF Hodges NJ Kel J , et al. The roles of talent, physical precocity and practice in the development of soccer expertise. J Sports Sci 2000; 18: 727–736.

14.
Helsen WF Starkes JL Hodges NJ . Team sports and the theory of deliberate practice. J Sport Exerc Psychol 1998; 20: 12–34.

15.
Hodge T Deakin JM . Deliberate practice and expertise in the martial arts: the role of context in motor recall. J Sport Exerc Psychol 1998; 20: 260–279.

16.
Hodges NJ Starkes JL . Wrestling with the nature of expertise: a sport specific test of Ercisson, Krampe and Tesch-Römer’s (1993) theory of “deliberate practice”. Int J Sport Psychol 1996; 27: 400–424.

17.
Law MP Côté J Ericsson KA . Characteristics of expert development in rhythmic gymnastics: a retrospective study. Int J Sport Exerc Psychol 2007; 5: 82–103.

18.
Starkes JL Deakin JM Allard F . Deliberate practice in sports: what is it anyway? In: Ericsson KA (eds) The road to excellence: the acquisition of expert performance in the arts, sciences, sports and games. Mahwah: Erlbaum, 1996, pp.81–106.

19.
Ward P Hodges NJ Starkes JL , et al. The road to excellence: deliberate practice and the development of expertise. High Ability Studies 2007; 18: 119–153.

20.
Newell A Rosenbloom PS . Mechanism of skill acquisition and the law of practice. In: Anderson JR (eds) Cognitive skills and their acquisition. Hillsdale: Erlbaum, 1981, pp.1–55.

21.
Balyi I Way R Higgs C . Long-term athlete development: a guide to developing a philosophy of sport for life, training framework and consistently successful organization. Champaign, IL: Human Kinetics, 2013.

22.
Harari YN . Homo Deus: a brief history of tomorrow. London: Signal Books, 2016.

23.
Carder SL Giusti NE Vopat LM , et al. The concept of sport sampling versus sport specialization: preventing youth athlete injury: a systematic review and meta-analysis. Am J Sports Med 2020; 48: 2850–2857.

24.
Giusti NE Carder SL Vopat L , et al. Comparing burnout in sport-specializing versus sport-sampling adolescent athletes: a systematic review and meta-analysis. Orthop J Sports Med 2020; 8: 2325967120907579.

25.
Brenner JS . Sports specialization and intensive training in young athletes. Pediatrics 2016; 138: 251–257.

26.
Goodway JD Robinson LE . Developmental trajectories in early sport specialization: a case for early sampling from a physical growth and motor development perspective. Kinesiol Rev 2015; 4: 267–278.

27.
Emmet D Roberts J Yao KV . Update on preventing overuse injuries in youth athletes. Curr Phys Med Rehabil Rep 2022; 10: 248–256.

28.
Smith AD Alleyne JMK Pitsiladis Y , et al. Early sports specialization: an international perspective. Curr Sports Med Rep 2017; 16: 439–442.

29.
Mosher A Till K Fraser-Thomas J , et al. Revisiting early sport specialization: what’s the problem? Sports Health 2022; 14: 13–19.

30.
Côté J Allan V Turnnidge J , et al. Early sport specialization and sampling. In: Tenenbaum G Eklund RC (eds) Handbook of sport psychology. 4th ed. Hoboken, NJ: Wiley, 2020, pp.578–594.

31.
Larson HK Young BW McHugh T-LF , et al. Markers of early specialization and their relationships with burnout and dropout in swimming. J Sport Exerc Psychol 2019; 41: 46–54.

32.
Downing C Redelius K Nordin-Bates S . Early specialisation among Swedish aesthetic performers: exploring motivation and perceptions of parental influence. Int J Sport Exerc Psychol 2022; 20: 1013–1032.

33.
Forsman H Blomqvist M Davids K , et al. The role of sport-specific play and practice during childhood in the development of adolescent Finnish team sport athletes. Int J Sports Sci Coach 2016; 11: 69–77.

34.
Ross KA Fried JW Bloom DA , et al. The effect of specialization and level of competition on injury in elite male ice hockey players. Phys Sportsmed 2022; 50: 295–300.

35.
Stegmann P Sieghartsleitner R Zuber C , et al. Successful talent development in popular game sports in Switzerland: the case of ice hockey. Int J Sports Sci Coach 2021; 16: 710–721.

36.
Meisel PL DiFiori JP Côté J , et al. Age of early specialization, competitive volume, injury, and sleep habits in youth sport: a preliminary study of US youth basketball. Sports Health 2022; 14: 30–44.

37.
Ford PR Hodges NJ Broadbent D , et al. The developmental and professional activities of female international soccer players from five high-performing nations. J Sports Sci 2020; 38: 1432–1440.

38.
Hendry DT Hodges NJ . Early majority engagement pathway best defines transitions from youth to adult elite men’s soccer in the UK: a three time-point retrospective and prospective study. Psychol Sport Exerc 2018; 36: 81–89.

39.
Zibung M Conzelmann A . The role of specialisation in the promotion of young football talents: a person-oriented study. Eur J Sport Sci 2013; 13: 452–460.

40.
DiFiori JP Benjamin HJ Brenner JS , et al. Overuse injuries and burnout in youth sports: a position statement from the American Medical Society for Sports Medicine. Br J Sports Med 2014; 48: 287–288.

41.
Waldron S DeFreese JD Register-Mihalik J , et al. The costs and benefits of early sport specialization: a critical review of literature. Quest 2020; 72: 1–18.

42.
Conzelmann A Zibung M Zuber C . Talente finden und fördern im Sport [Finding and promoting talent in sport]. In: Ritz A Thom N (eds) Talent Management: Talente identifizieren, Kompetenzen entwickeln, Leistungsträger erhalten. 3 ed. Wiesbaden: Springer Gabler, 2018, pp.87–104.

43.
Benson PL Scales PC Hamilton SF , et al. Positive youth development: theory, research, and applications. In: Damon W Lerner RM (eds) Handbook of child psychology. Hoboken: John Wiley & Sons, 2007, pp.894–941.

44.
Lloyd RS Oliver JL Faigenbaum AD , et al. Long-term athletic development, part 1: a pathway for all youth. J Strength Cond Res 2015; 29: 1439–1450.

45.
Rongen F McKenna J Cobley S , et al. Are youth sport talent identification and development systems necessary and healthy? Sports Med Open 2018; 4: 18.

46.
Bell DR Snedden T Biese K , et al. Consensus definition of sport specialization in youth athletes using a Delphi approach. J Athl Train 2021; 56: 1239–1251.

47.
Ford PR Ward P Hodges NJ , et al. The role of deliberate practice and play in career progression in sport: the early engagement hypothesis. High Ability Studies 2009; 20: 65–75.

48.
Mosher A Fraser-Thomas J Baker J . What defines early specialization: a systematic review of literature. Front Sports Act Living 2020; 2: 596229.

49.
Voigt L Hohmann A . Expert youth coaches’ diversification strategies in talent development: a qualitative typology. Int J Sports Sci Coach 2016; 11: 39–53.

50.
Eccles DW Leone EJ Williams AM . Deliberate practice: what is it and how can I use it? J Sport Psychol Action 2022; 13: 16–26.

51.
Sieghartsleitner R Zuber C Zibung M , et al. “The early specialised bird catches the worm!” ─ a specialised sampling model in the development of football talents. Front Psychol 2018; 9: 1–12.

52.
Baker J Johnston K Wojtowicz M , et al. What do we really know about elite athlete development? Limitations and gaps in current understanding. Br J Sports Med 2022; 56: 1331–1332.

53.
Tan CWK Chow JY Davids K . ‘How does TGfU work?’: examining the relationship between learning design in TGfU and a nonlinear pedagogy. Phys Educ Sport Pedagogy 2012; 17: 331–348.

54.
Anderson DI Steel KA . It’s not the type of practice that matters, it’s the attitude: the impact of playful practice on motor skill learning. BJMB 2022; 16: 179–193.

55.
Côté J Lidor R Hackfort D . ISSP position stand: to sample or to specialize? Seven postulates about youth sport activities that lead to continued participation and elite performance. Int J Sport Exerc Psychol 2009; 7: 7–17.

56.
Herman DC Nelson VR Montalvo AM , et al. Systematic review of health organization guidelines following the AMSSM 2019 youth early sport specialization summit. Sports Health 2022; 14: 127–134.

57.
Kliethermes SA Nagle K Côté J , et al. Impact of youth sports specialisation on career and task-specific athletic performance: a systematic review following the American Medical Society for Sports Medicine (AMSSM) collaborative research network’s 2019 youth early sport specialisation summit. Br J Sports Med 2020; 54: 221–230.

58.
Baker J Mosher A Fraser-Thomas J . Is it too early to condemn early sport specialisation? Br J Sports Med 2021; 55: 179–180.

59.
Baltes PB Lindenberger U Staudinger UM . Life span theory in developmental psychology. In: Damon W Lerner RM (eds) Handbook of child psychology. Hoboken: John Wiley & Sons, 2007, pp.569–664.

60.
Kluckhohn C Murray HA . Personality in nature, society, and culture. New York: Knopf, 1948.

61.
Lerner RM . Developmental science, developmental systems, and contemporary theories of human development. In: Damon W Lerner RM (eds) Handbook of child psychology. Hoboken: John Wiley & Sons, 2007, pp.1–17.

62.
Schlesinger T Löbig A Ehnold P , et al. What is influencing the dropout behaviour of youth players from organised football? Ger J Exerc Sport Res 2018; 48: 176–191.

63.
Lerner RM Lerner JV . The development of a person: a relational-developmental systems perspective. In: McAdams DP Shiner RL Tackett JL (eds) Handbook of personality development. New York: The Guilford Press, 2019, pp.59–78.

64.
Barth M Güllich A Macnamara BN , et al. Predictors of junior versus senior elite performance are opposite: a systematic review and meta-analysis of participation patterns. Sports Med 2022; 52: 1399–1416.

65.
Chaabene H Lesinski M Behm DG , et al. Performance - and health-related benefits of youth resistance training. Sports Ortho Traum 2020; 36: 231–240.

66.
Lloyd RS Oliver JL . The youth physical development model: a new approach to long-term athletic development. J Strength Cond Res 2012; 34: 61–72.

67.
Pichardo AW Oliver JL Harrison CB , et al. Integrating models of long-term athletic development to maximize the physical development of youth. Int J Sports Sci Coach 2018; 13: 1189–1199.

68.
Bergeron MF Mountjoy M Armstrong N , et al. International Olympic Committee consensus statement on youth athletic development. Br J Sports Med 2015; 49: 843–851.

69.
Windelband W . Geschichte und Naturwissenschaft [History and natural science]. 3rd ed. Strassburg: Heitz, 1904.

70.
Raeff C . Exploring the dynamics of human development: an integrative approach. New York: Oxford University Press, 2016.

71.
Werner H . The concept of development from a comparative and organismic point of view. In: Harris DB (eds) The concept of development. Minneapolis: University of Minnesota Press, 1957, pp.125–148.

72.
Lövdén M Bäckman L Lindenberger U , et al. A theoretical framework for the study of adult cognitive plasticity. Psychol Bull 2010; 136: 659–676.

73.
McNeil MC Polloway EA Smith JD . Feral and isolated children: historical review and analysis. Educ Train Ment Retard 1984; 19: 70–79.

74.
Gabard-Durnam L McLaughlin KA . Sensitive periods in human development: charting a course for the future. Curr Opin Behav Sci 2020; 36: 120–128.

75.
Werker JF Hensch TK . Critical periods in speech perception: new directions. Annu Rev Psychol 2015; 66: 173–196.

76.
Penhune VB . Sensitive periods in human development: evidence from musical training. Cortex 2011; 47: 1126–1137.

77.
Lloyd RS Moeskops S Granacher U . Motor skill training for young athletes. In: Lloyd RS Oliver JL (eds) Strength and conditioning for young athletes: science and application. 2nd ed. New York: Routledge, 2020, pp.103–130.

78.
Solum M Lorås H Pedersen AV . A golden age for motor skill learning? Learning of an unfamiliar motor task in 10-year-olds, young adults, and adults, when starting from similar baselines. Front Psychol 2020; 11: 538.

79.
van Hooren B de Ste Croix M . Sensitive periods to train general motor abilities in children and adolescents: do they exist? A critical appraisal. J Strength Cond Res 2020; 42: 7–14.

80.
Knudsen EI . Sensitive periods in the development of brain and behavior. J Cogn Neurosci 2004; 16: 1412–1425.

81.
Hartshorne JK Tenenbaum JB Pinker S . A critical period for second language acquisition: evidence from 2/3 million English speakers. Cognition 2018; 177: 263–277.

82.
Anderson DI Mayo AM , et al. Windows of optimal development. In: Baker J Cobley S Schorer J (eds) Routledge handbook of talent identification and development in sport. London: Routledge, 2017, pp.221–235.

83.
Rowland TW . The ‘trigger hypothesis’ for aerobic trainability: a 14-year follow-up. Pediatr Exerc Sci 1997; 9: 1–9.

84.
Rowland TW . Physiological aspects of early specialized athletic training in children. Kinesiol Rev 2015; 4: 279–291.

85.
Katch VL . Physical conditioning of children. J Adolesc Health Care 1983; 3: 241–246.

86.
Armstrong N Barker AR . Endurance training and elite young athletes. Med Sport Sci 2011; 56: 84–96.

87.
Ford PR Williams AM , et al. Sport activity in childhood: early specialization and diversification. In: Baker J Cobley S Schorer J (eds) Routledge handbook of talent identification and development in sport. London: Routledge, 2017, pp.117–132.

88.
Hossner EJ Künzell S . Einführung in die Bewegungswissenschaft [Introduction in movement science]. Wiebelsheim: Limpert, 2022.

89.
Henry FM . Specificity vs. generality in learning motor skill. In: Brown RC Kenyon GS (eds) Classical studies on physical activity. Englewood Cliffs: Prentice Hall, 1968, pp.33–340.

90.
Hossner EJ Kredel R Franklin D . Practice. In: Hackfort D Schinke RJ (eds) The Routledge international encyclopedia of sport and exercise psychology. London: Routledge, 2020, pp.532–554.

91.
Oppici L Panchuk D . Specific and general transfer of perceptual-motor skills and learning between sports: a systematic review. Psychol Sport Exerc 2021; 59: 102118.

92.
Kliethermes SA Marshall SW LaBella CR , et al. Defining a research agenda for youth sport specialization in the United States: the AMSSM youth early sport specialization summit. Clin J Sport Med 2021; 31: 103–112.

93.
Woodworth RS EL T . The influence of improvement in one mental function upon the efficiency of other functions. Psychol Rev 1901; 8: 247–261.

94.
d’Avella A . Modularity for motor control and motor learning. Adv Exp Med Biol 2016; 957: 3–19.

95.
Fodor JA . The modularity of mind. Cambridge: MIT Press, 1983.

96.
Hossner EJ . Module der Motorik [Motor skills modules]. Schorndorf: Hofmann, 1995.

97.
Wolpert DM . Computational approaches to motor control. Trends Cogn Sci 1997; 1: 209–216.

98.
Wormhoudt R Savelsbergh GJ Teunissen J , et al. The athletic skills model: optimizing talent development through movement education. Oxon: Routledge, 2017.

99.
Hottenrott K Neumann G . Methodik des Ausdauertrainings [Methods for endurance training]. 2nd ed. Schnorndorf: Hofmann, 2010.

100.
Schärer C Reinhart L Hübner K . Age-related differences between maximum flight height of basic skills on floor, beam and vault and physical condition of youth female artistic gymnasts. Sports 2023; 11: 100.

101.
Schweizer Radio und Fernsehen. Vater Odermatt: Persönlicher Statistiker für den Sohn [Father Odermatt: personal statistician for the son] , https://www.srf.ch/play/tv/beijing-heute/video/vater-odermatt-persoenlicher-statistiker-fuer-den-sohn?urn=urn:srf:video:b675a0a4-cf87-4b51-a909-ddf0e46581cb (accessed 6 June 2022).

102.
Bailey R , et al. The child’s right to an open sporting future. In: Bailey R Agans JP Côté J (eds) Physical activity and sport during the first ten years of life. New York, NY: Routledge, 2021, pp.124–138.

103.
Haraldsen HM Nordin-Bates SM Abrahamsen FE , et al. Thriving, striving, or just surviving? TD learning conditions, motivational processes and well-being among Norwegian elite performers in music, ballet, and sport. Roeper Rev 2020; 42: 109–125.

104.
Erickson K Côté J Turnnidge J , et al. Play during childhood and the development of expertise in sport. In: Hambrick DZ Campitelli G Macnamara BN (eds) The science of expertise: behavioral, neural and genetic approaches to complex skill. New York/London: Routledge, 2018, pp.398–416.

105.
Faigenbaum AD Meadors L . A coaches dozen: 12 FUNdamental principles for building young and healthy athletes. J Strength Cond Res 2010; 32: 99–101.

106.
Lloyd RS Cronin JB Faigenbaum AD , et al. National strength and conditioning association: position statement on long-term athletic development. J Strength Cond Res 2016; 30: 1491–1509. www.nsca.com (2016).

107.
Jayanthi N Saffel H Gabbett T . Training the specialised youth athlete: a supportive classification model to keep them playing. Br J Sports Med 2021; 55: 1248–1249.

108.
Jayanthi N Schley S Cumming SP , et al. Developmental training model for the sport specialized youth athlete: a dynamic strategy for individualizing load-response during maturation. Sports Health 2021; 14: 19417381211056088.

109.
Lloyd RS Faigenbaum AD Stone MH , et al. Position statement on youth resistance training: the 2014 International Consensus. Br J Sports Med 2014; 48: 498–505.

110.
Myer GD Lloyd RS Brent JL , et al. How young is too young to start training? ACSM’s Health and Fitness Journal 2013; 17: 14–23.

111.
Vallerand RJ Losier GF . An integrative analysis of intrinsic and extrinsic motivation in sport. J Appl Sport Psychol 1999; 11: 142–169.

112.
Deci EL Ryan RM . Intrinsic motivation and self-determination in human behavior. New York: Plenum, 1985.

113.
Occhino JL Mallett CJ Rynne SB , et al. Autonomy-supportive pedagogical approach to sports coaching: research, challenges and opportunities. Int J Sports Sci Coach 2014; 9: 401–415.

114.
Weiss MR (ed). Developmental sport and exercise psychology: a lifespan perspective. Morgantown: Fitness Information Technology, 2004.

115.
White SA . Parent-created motivational climate. In: Jowett S Lavallee D (eds) Social psychology in sport. Champaign: Human Kinetics, 2007, pp.131–143.

116.
Conzelmann A Schmidt M Valkanover S . Persönlichkeitsentwicklung durch Schulsport: Theorie, Empirie und Praxisbausteine der Berner Interventionsstudie Schulsport (BISS): [Personality development through school sport: theory, empiricism and practical components of the Bern Intervention Study School Sport (BISS)]. Bern: Hans Huber, 2011.

117.
Schmidt M Valkanover S Roebers C , et al. Promoting a functional physical self-concept in physical education: evaluation of a 10-week intervention. Eur Phy Educ Rev 2013; 19: 232–255.

118.
Dunn R Tamminen K . A scoping review of the use of theory in positive youth development and athlete transition literature. Int Rev Sport Exerc Psychol 2023: 1–24.

119.
Lerner RM Almerigi JB Theokas C , et al. Positive youth development: a view of the issues. J Early Adolesc 2005; 25: 10–16.

120.
Gutzwiller R . Skandal im Schweizer Sport: Die erschreckende Wahrheit der Magglingen-Protokolle - Wie Spitzenturnerinnen gebrochen werden [Scandal in Swiss sport: the shocking truth of the Magglingen protocols: how top gymnasts are broken]. Aargauer Zeitung, 1 November 2020.

121.
Gertsch C Krogerus M . Misshandlungen im Schweizer Sport: Die Magglingen-Protokolle [Abuses in Swiss sport: the Magglingen Protocols]. Tagesanzeiger, 31 October 2020.

122.
Steinke I . Gütekriterien qualitativer forschung. In: Flick U von Kardorff E Steinke I (eds) Qualitative Forschung: Ein Handbuch. 8th ed. Hamburg: Rowholts, 2010, pp.319–331.

123.
Lincoln YS Guba EG . Naturalistic inquiry. Newbury Park: Sage, 1985.

124.
Richters JE . Incredible utility: the lost causes and causal debris of psychological science. Basic Appl Soc Psych 2021; 43: 366–405.

125.
Plomin R . Blueprint: how DNA makes us who we are. London: Allen lane, 2018.

126.
Cumming SP Sherar LB Pindus DM , et al. A biocultural model of maturity-associated variance in adolescent physical activity. Int Rev Sport Exerc Psychol 2012; 5: 23–43.

127.
Zuber C Sieghartsleitner R Zibung M , et al. Who made it to the pros?” A 5-year longitudinal study on the role of achievement motivation in football. Int J Sport Psychol 2022; 53: 75–82.

128.
Spence JC Lee RE . Toward a comprehensive model of physical activity. Psychol Sport Exerc 2003; 4: 7–24.

129.
Hohmann A Singh A Voigt L . Konzepte erfolgreichen Nachwuchstrainings (KerN): Abschlussbericht zum Forschungsprojekt “Langfristiger Leistungsaufbau im Nachwuchsleistungssport” [Concepts of successful youth training (KerN): final report on the research project “Long-term performance development in youth elite sport”]. Hellenthal: Sportverlag Strauss, 2017.

130.
Bouchard C An P Rice T , et al. Familial aggregation of VO(2max) response to exercise training: results from the HERITAGE family study. J Appl Physiol (1985) 1999; 87: 1003–1008.

131.
Malina RM . Youth sports: readiness, selection and trainability. In: Duquet W Day JAP (eds) Kinanthropometry IV. London: E & FN Spon, 1993, pp.252–266.

132.
Lindenberger U Lövdén M . Brain plasticity in human lifespan development: the exploration–selection–refinement model. Annu Rev Dev Psychol 2019; 1: 197–222.

133.
Baker J Schorer J Wattie N . Compromising talent: issues in identifying and selecting talent in sport. Quest 2018; 70: 48–63.

134.
Höner O Murr D Larkin P , et al. Nationwide subjective and objective assessments of potential talent predictors in elite youth soccer: an investigation of prognostic validity in a prospective study. Front Sports Act Living 2021; 3: 638227.

135.
Wachsmuth S Feichtinger P Bartley J , et al. Psychological characteristics and future success: a prospective study examining youth soccer players at different stages within the German talent development pathway. J Appl Sport Psychol 2023: 1–25: 638227.

136.
Schmid MJ Charbonnet B Conzelmann A , et al. More success with the optimal motivational pattern? A prospective longitudinal study of young athletes in individual sports. Front Psychol 2021; 11: 606272.

137.
Lenze L Zibung M Zuber C , et al. International performance level in adult ice hockey: the role of the talent environment in youth. J Sports Sci 2023; 41: 1–12.

138.
Zibung M Conzelmann A . National youth team football players between the conflicting priorities of sports success and vocational training. Eur J Sport Soc 2014; 11: 127–150.

139.
Hauser L-L Harwood CG Höner O , et al. Talent development environments within sports: a scoping review examining functional and dysfunctional environmental features. Int Rev Sport Exerc Psychol 2022: 1–27.

140.
Kristensen JÅ Skilbred A Abrahamsen FE , et al. Performance-enhancing and health-compromising behaviors in youth sports: a systematic mixed-studies review. Perform Enhanc Health 2022; 10: 100237.

141.
Juul J . Dein selbstbestimmtes Kind: Unterstützung der Eltern, deren Kindern früh nach Autonomie streben [Your self-determined child: supporting parents whose children strive for autonomy at an early age]. München: Kösel, 2020.

142.
Harris JJ Collins D Nash C . Let’s hear it from the kids! Examining the experiences, views, and needs of highly committed children involved in youth sport. Sport Psychol 2023; 37: 1–11.

143.
Verner-Filion J Vallerand RJ Amiot CE , et al. The two roads from passion to sport performance and psychological well-being: the mediating role of need satisfaction, deliberate practice, and achievement goals. Psychol Sport Exerc 2017; 30: 19–29.

144.
Vallerand RJ Mageau GA Elliot AJ , et al. Passion and performance attainment in sport. Psychol Sport Exerc 2008; 9: 373–392.

145.
Bornstein MH . The specificity principle in acculturation science. Perspect Psychol Sci 2017; 12: 3–45.

146.
Peters CM Hendry DT Hodges NJ . A scoping review on developmental activities of girls’ and women’s sports. Front Sports Act Living 2022; 4: 903886.

147.
Bergman LR Magnusson D El-Khouri BM . Studying individual development in an interindividual context: a person-oriented approach. London: Psychology Press, 2003.

148.
Zuber C Zibung M Conzelmann A . Holistic patterns as an instrument for predicting the performance of promising young soccer players─a 3-years longitudinal study. Front Psychol 2016; 7: 1–10.