4.1 Volume of Sport-Specific Practice and Training
Despite wide variation across sports, most junior elite, elite and super-elite athletes have accumulated enormous volumes of organized practice and training [
149,
230,
241‐
260]. Extensive sport-specific deliberate practice (DP) is thus a pre-requisite to world-class performance in sports with a large participant base.
A widely held view, based on seminal work in chess [
261] and music [
262], is that 10 years and 10,000 h of DP are necessary and sufficient to reach expert level [
27,
31]. Indeed, many elite and super-elite athletes have been practicing and training for ten years or longer [
230,
241,
243‐
245,
248]. In discussing his DP framework, however, Ericsson [
263] has recently emphasized he did not intend for his original (i.e. 1993 [
262]) conclusions to constitute a 10,000 h ‘rule’. In fact, there is considerable variation within and across sports at elite and super-elite level [
10,
23,
264], with some data suggesting an average time from novice to senior national representation of just 7.5 years, and even Olympic level in just 14 months [
265]. Evidence at super-elite level suggests as few as 4400 h may lead to Olympic Gold in field hockey [
236], and 4500 h to representing the German national soccer team [
266], with just 4000 h sufficient to reach elite and super-elite levels in basketball, field hockey and netball [
241]. Interestingly, organized practice/training has been shown at junior elite [
267] and super-elite level [
266] to comprise considerable non-DP activity (e.g. play).
DP theory also asserts [
262] that the more DP accumulated, the higher the performance attained. There is evidence that more successful athletes have averaged larger amounts of organized sport-specific practice/training. These observations are based on comparisons of non-elite athletes with: junior elite athletes in cricket and soccer [
246,
259,
260]; elite athletes in basketball, cricket, field hockey, handball, soccer, swimming, triathlon and wrestling [
243,
248,
250,
255,
260]; and super-elite athletes in basketball, darts, field hockey and netball [
241,
245], and also on comparisons of adolescent elite with super-elite rhythmic gymnasts [
254]. Additionally, elite Australian Rules footballers with better perceptual/decision-making skills performed more domain-specific practice than less skilled players [
244]. Differences in the amounts of organized domain-specific practice/training were, however, only significant in these studies for data referring to training in late adolescence and adulthood, not training at younger ages (except rhythmic gymnastics [
254]).
Such differences have not been observed between super-elite and elite athletes in field hockey, soccer, tennis, swimming [
203,
236,
253,
266] and across all Olympic sports (including athletics, badminton, basketball, fencing, figure skating, gymnastics, judo, rowing, soccer, swimming, table tennis and wrestling) [
20,
230]. The opposite effect has also been noted, with super-elite field hockey players training significantly less than their elite peers [
258]. No consistent differences have been reported with regard to the volume of competition experienced between different success levels [
241,
244‐
246,
259].
Although the DP framework has gained popularity in sport science and in popular literature, its applicability to high-performance sport may be limited. The suggestion of 10 years/10,000 h was originally based on: (a) musicians, not outstanding athletes; and (b) a strict interpretation of DP, excluding intrinsically enjoyable activities, team practice, play, competition, non-organized sporting activities, and also ruling out implicit (improved task performance in the absence of conscious awareness) and incidental learning (learning in the absence of an intention to learn). DP also implies full attention and concentration, while research indicates that full concentration does not always generate optimal learning/performance. Increasing conscious awareness may even result in poorer performance (e.g. paralysis by analysis [
268]; the regression hypothesis [
176]—(i.e., regressing to a performance level akin to earlier learning). Evidence at non-elite level [
176,
269] also indicates that implicit learning leads to more robust performance under pressure. Finally, evidence at junior elite [
246,
259,
260,
270], elite [
242,
244] and super-elite level [
241,
245,
266] demonstrates that organized and non-organized play is an important component of (early) experiences of developing sporting experts.
With moderate/high study design, moderate consistency and high direct relevance (up to super-elite level), the quality of evidence that extensive DP is an important contributor to the development of super-elite performance in sport is high to moderate, while high/moderate quality of evidence suggests that the applicability of the 10 years/10,000 h rule is limited and that DP alone does not guarantee sporting success. Additionally, the contribution of practice/training to the development of sporting expertise may only apply to domain-specific practice accrued during late adolescence or adulthood, with practice volume not discriminating elite from super-elite athletes. Finally, there is some low quality evidence to suggest that automaticity and implicit learning may contribute to the development of sporting expertise. We therefore recommend that policy makers and practitioners continue to promote deliberate practice, but consider the present evidence before routinely increasing practice volumes with junior athletes, and acknowledge the potential benefits of automaticity, implicit learning and also enjoyment in practice and play. The links between early sport-specific practice/training and short- and long-term outcomes are a research priority. How is intensified specific training related to long-term enjoyment, motivation, stress-recovery and prolonged involvement? Future research should also further explore the roles of explicit and implicit/incidental learning in the development of expert performance. This implies scrutiny of the intentions and specific activities performed during practice/training and play, their combinations, variability, potential interactions and relative influence through different developmental age ranges.
4.2 Early Specialization Versus Sampling and Play
Where peak performance in sport is achieved before biological maturity, early specialization may be necessary to reach elite level. For example, super-elite athletes in artistic composition sports (artistic gymnastics, figure skating, platform diving and rhythmic gymnastics [
230]) performed three to seven times more sport-specific training until age 10 years compared to all other types of Olympic sports. Their volumes of practice/training did not, however, differ from their elite counterparts
within their respective sports. A super-elite sample of rhythmic gymnasts also experienced reduced involvement in other sports compared to their elite counterparts [
254]. However, evidence at non-elite, junior elite, elite and super-elite level suggests that many athletes have not progressed exclusively within one discipline, but have practiced multiple sports during childhood and adolescence [
230,
236,
241‐
244,
260,
270‐
274]. Further, evidence from non-elite and super-elite data [
254,
275‐
278] points to the potential costs and risks associated with early specific practice, training and competitions (e.g. less enjoyment, time demands, restricted activities outside sport, exhaustion, overuse injuries and increased risk of dropout). Comparisons between super-elite and elite athletes from field hockey, soccer, tennis and 47 Olympic sports [
203,
230,
236,
266] have even demonstrated larger volumes of practice/training and/or play in other sports among the super-elite, mostly associated with a later start in their main sport and a later specialization.
There is also evidence at non-elite, junior elite, elite and super-elite level that many athletes have spent considerable time in non-organized play during childhood [
39,
241,
244,
246,
255,
259,
260,
270]. A positive relationship between non-organized play and junior elite [
246,
260] and super-elite success [
266] has been noted, but equally other studies have noted no differences between performance levels, with some demonstrating more play among non-elite compared with elite/super-elite athletes [
236,
241,
244,
245,
255,
259,
260]. Elite and non-elite soccer players [
279] could be differentiated by a
combination of above-average volume of organized soccer training/practice with
either above-average involvement in other sports
or above-average non-organized soccer play.
With moderate study design, moderate (early sampling of diverse sports, late specialization)/low (play) consistency, and high direct relevance (up to super-elite level), the quality of the evidence that early specialization or sampling represent the best route to the development of super-elite performance in sport is moderate. Both early specialization and sampling (and play) may be routes to expertise under optimal conditions. However, the probability of attaining elite or super-elite level may be enhanced by the coupling of a large volume of intensive, organized specific training/practice in the main sport with appreciable amounts of organized training/practice and competitions in other sports and/or non-organized play in the main or other sports. We thus recommend policy makers and practitioners to draw on this evidence, bearing in mind the need to minimize the potential hazards of early specialization when such specialization is necessary, and with regard to promoting opportunities for young athletes to experience non-organized play and sampling in a variety of sports. Future research is needed to understand how participation in various sports benefits super-elite performance in one main sport. Further, how does the process of late specialization following prior diversification or ‘talent transfer’ proceed? Are there certain sports or clusters that lay the best foundation for super-elite success in a final sport?