Table 4.
Definitions provided for all studies.
| References | Definition provided | Year round | Intense training | Single sport | Exclusion of other sports | Young age | Deliberate practice |
|---|---|---|---|---|---|---|---|
| American Academy of Pediatrics (2000) | None | ||||||
| Anderson and Mayo (2015) | Exclusive participation in a single sport on a year-round basis, with a primary focus on training and development in that sport. | Yes | Yes | Yes | Yes | ||
| Arede et al. (2019) | None | ||||||
| Baker and Robertson-Wilson (2003) | Limiting sport participation to a single sport with the specific goal of guiding the child athlete to top achievement | Yes | Yes | ||||
| Baker et al. (2005) | A shift from activities that are play like in nature to more structured and effortful training activities. In addition, the number of sport-specific training hours dramatically increases from initial involvement in the sampling years to committed involvement in the investment years | ||||||
| Baker et al. (2009) | Four specific parameters: early start age in sport; early involvement in one sport (as opposed to participating in several sports); early involvement in focused, high intensity training; and early involvement in competitive sport | Yes | Yes | Yes | |||
| Baker (2003) | To limit their childhood sport participation to a single sport, with a deliberate focus on training and development in that sport | Yes | Yes | ||||
| Beese et al. (2015) | Year-round participation in a single sport to the exclusion of other sports and activities | Yes | Yes | Yes | |||
| Bell et al. (2016) | Year-round intensive training in a single sport at the exclusion of other sports | Yes | Yes | Yes | Yes | ||
| Bell et al. (2018c) | Participation in a single sport at the exclusion of other sports | Yes | Yes | ||||
| Bell et al. (2018b) | Year-round participation in sport at the exclusion of other sports | Yes | Yes | Yes | |||
| Bell et al. (2018a) | Intense, year-round training in a single sport and may include the exclusion of other sports | Yes | Yes | Yes | Yes | ||
| Bell (2018) | None | ||||||
| Black et al. (2019) | Participation in ice hockey at the exclusion of other sports at or before the age of 12 years | Yes | Yes | Yes | |||
| Blagrove et al. (2017) | Training routines that focus on intensive training in a single sport (for 0.8 mo/y), or a total weekly training volume which exceeds the athletes' age in years, until late adolescence | Yes | Yes | ||||
| Bodey et al. (2013) | Emphasizes focused training in a single sport on a year-round basis | Yes | Yes | ||||
| Branta (2010) | None | ||||||
| Brenner (2016) | An athlete focuses on only 1 sport, usually at the exclusion of any other and often year-round | Yes | Yes | Yes | |||
| Bridge and Toms (2013) | Continual year-round training and development in a single sport between the ages of 6 and 12 years | Yes | Yes | Yes | |||
| Brooks et al. (2018) | Specialize in a single sport at the exclusion of other sports | Yes | Yes | ||||
| Brylinsky (2010) | None | ||||||
| Buckley et al. (2017) | intense, year-round [8 months/year] training in a single sport with the exclusion of other sports | Yes | Yes | Yes | Yes | ||
| Buhrow et al. (2017) | Engaging in year-round training in one regulated, competitive sport at the elimination of all other sports | Yes | Yes | Yes | |||
| Callender (2010) | None | ||||||
| Capranica and Millard-Stafford (2011) | As the age or point in time in an athlete's development when sports training and competition is restricted to and focused upon a single sport in the pursuit of elite performance | Yes | |||||
| Carson et al. (2010) | None | ||||||
| Coakley (2010) | Year-round specialization in a single sport | Yes | Yes | ||||
| Côté and Hancock (2016) | None | ||||||
| Côté et al. (2009) | Investing in one sport on a year round basis from a young age with the goal of developing expertise | Yes | Yes | Yes | |||
| Côté et al. (2009) | A high volume of deliberate practice and a low amount of deliberate play in one sport and focuses on performance as early as age six or seven | Yes | Yes | ||||
| Coutinho et al. (2015) | An early start age in doing one specific sport and an early investment in deliberate practice (i.e., highly structured and intensive activities, with the explicit goal of improving performance) | Yes | Yes | Yes | Yes | ||
| Cupples et al. (2018) | Single-sport involvement, low deliberate play and progressive investment in deliberate practice with age | Yes | Yes | ||||
| DePhillipo et al. (2018) | Intense training year-round in a specific sport starting at a young age | Yes | Yes | Yes | Yes | ||
| DiCesare et al. (2019) | A year- or near year-round commitment to one sport at the exclusion of others | Yes | Yes | Yes | |||
| DiFiori et al. (2017) | None | ||||||
| DiFiori et al. (2014) | Intensive, year-round training in a single sport at the exclusion of other sports | Yes | Yes | Yes | Yes | ||
| DiSanti and Erickson (2019) | Intensive year-round training in a single sport at the exclusion of other sports | Yes | Yes | Yes | Yes | ||
| DiStefano et al. (2018) | Only participate in 1 sport at an early age, with goals of achieving elite athletic success | Yes | Yes | ||||
| Fabricant et al. (2016) | Year-round intensive training in a single sport at the exclusion of other sports | Yes | Yes | Yes | Yes | ||
| Feeley et al. (2016) | Intensive, year-round training in a single sport to the exclusion of other sports | Yes | Yes | Yes | Yes | ||
| Ferguson and Stern (2014) | Intense year round training in a specific sport with the exclusion of other sports at a young age | Yes | Yes | Yes | Yes | Yes | |
| Ford et al. (2012) | Begin during childhood in relatively high intensity practice and competition in their primary sport. They engage in relatively little play activity in the primary sport and in relatively few or no other sports during this period. It usually also involves identification and selection into a talent development programme in the primary sport during childhood | Yes | Yes | Yes | |||
| Fransen et al. (2012) | Enter their primary sport at an early age and participate in a high amount of deliberate practice in their primary sport with almost no deliberate play in any other sports | Yes | Yes | ||||
| Gallant et al. (2017) | Early sport specializers (i.e., high OPA level, low UPA level, and participation in 1 sport only) | Yes | |||||
| Geisler (2019) | Three primary criteria: (1) intensive training or competition in organized sports for more than 8 months per year, (2) participating in one sport to the exclusion of participation in others, and (3) involving pre-pubertal aged children prior to 12 years | Yes | Yes | Yes | Yes | ||
| Ginsburg et al. (2014) | Which necessitates a high volume of deliberate practice in a single sport as early as six or seven years of age and a purposeful focus on training and skill development | Yes | Yes | Yes | |||
| Gonçalves et al. (2012) | None | ||||||
| Goodway and Robinson (2015) | Focused involvement in one sport and a large number of hours of deliberate practice with the goal of improving sport skills and performance outcomes during childhood | Yes | Yes | Yes | |||
| Gould (2010) | None | ||||||
| Griffin (2008) | None | ||||||
| Güllich (2014) | Reinforced intensity and expansion of domain-specific practice, | Yes | |||||
| Güllich (2017) | Early concentration in one sport with reinforced sport specific DP/training that is subsequently expanded through all age periods | Yes | Yes | Yes | |||
| Güllich and Emrich (2014) | None | ||||||
| Güllich and Emrich (2013) | Represent the poles of a continuum differing in exclusivity and intensity of early, sport-specific practice/training, involvement in different sports and non-organized sport activities. | Yes | Yes | Yes | |||
| Hall et al. (2015) | With intense year-round training in a single sport at the exclusion of other sports or activities | Yes | Yes | Yes | Yes | ||
| Hastie (2015) | Intense, year-round training in a single sport with the exclusion of other sports | Yes | Yes | Yes | Yes | ||
| Haugaasen and Jordet (2012) | High amount of deliberate practice, low deliberate play, one sport | Yes | Yes | ||||
| Huxley et al. (2017) | High volumes of domain specific deliberate practice in one sport from an early age | Yes | Yes | Yes | |||
| Hill (1993) | Limited their participation to one sport which they practiced trained and competed in year round | Yes | Yes | ||||
| Horn (2015) | None | ||||||
| Jayanthi et al. (2015) | Year-round intensive training in a single sport at the exclusion of other sports | Yes | Yes | Yes | Yes | ||
| Jayanthi and Dugas (2017) | Year-round intense training in a single sport with the exclusion of other sports | Yes | Yes | Yes | Yes | ||
| Jayanthi et al. (2013) | Intense, year-round training in a single sport with the exclusion of other sports | Yes | Yes | Yes | Yes | ||
| Jayanthi et al. (2018) | Intensive, year-round training in a single sport at the exclusion of other sports | Yes | Yes | Yes | Yes | ||
| Kaleth and Mikesky (2010) | This practice typically involves children (ages 6 to 12) who commit almost exclusively to a single sport, train and compete year-round, and have high internal—and often external—expectations | Yes | Yes | Yes | |||
| Landers et al. (2010) | Specialization in one sport or in one position in a sport, at increasingly younger ages, in order to compete at the highest levels | Yes | Yes | ||||
| LaPrade et al. (2016) | 1. Participation in intensive training and/or competition in organized sports > 8 months per year (essentially year round) 34 2. Participation in 1 sport to the exclusion of participation in other sports (limited free play overall) 33 3. Involving pre-pubertal (seventh grade or roughly age 12 years) children. | Yes | Yes | Yes | Yes | Yes | |
| Larson et al. (2019) | (a) involving pre-pubertal children; who (b) participate in one sport to the exclusion of others, with limited free play overall; and (c) participate in intensive training and/or competition in organized sports for more than 8 months/year | Yes | Yes | Yes | Yes | ||
| Leite and Sampaio (2012) | Involved targeted involvement in a single sport | Yes | |||||
| Leite et al. (2009) | A shift from activities that are play-like in nature to more structured and effortful training activities. In addition, the number of sport-specific training hours dramatically increases from initial involvement in the sampling years to committed involvement in the investment years | ||||||
| Leite et al. (2013) | Limit their childhood sport participation to a single sport, with a deliberate focus on training and development in that sport | Yes | |||||
| Livingston et al. (2016) | Deliberate practice or training with the purpose of improving skills | Yes | |||||
| Malina (2010) | Specialized, systematic training in a single sport at a relatively young age with the goal of attaining elite status | Yes | Yes | ||||
| Martin et al. (2017) | Participate in a single sport on a year-round basis, with a focus on training and development in that single sport | Yes | Yes | ||||
| Mattson and Richards (2010) | Characterized by participation in specific, intense training for a single sport at a competitive level at an early age | Yes | Yes | Yes | |||
| Matzkin and Garvey (2019) | Intensive year-round training in a single sport at the exclusion of other sports | Yes | Yes | Yes | Yes | ||
| McDonald et al. (2019) | Intensive training/competition in organized sports >8 months per year, participation in one sport with the exclusion of all other sports, and involvement of children who are pre-pubertal or ~12 years of age | Yes | Yes | Yes | Yes | ||
| McFadden et al. (2016) | Specialize in one sport before the age of 12, youth engage in high amounts of deliberate practice in a single sport | Yes | Yes | Yes | |||
| McGuine et al. (2017) | None | ||||||
| McLeod et al. (2019) | Extensive year-round training in a single sport at the exclusion of others | Yes | Yes | Yes | |||
| Mendes et al. (2018) | Young children may have an early starting age in highly structured and intensive activities with the explicit goal of improving performance in a sport | Yes | |||||
| Miller et al. (2017) | Year-round intensive training in a single sport at the exclusion of other sports | Yes | Yes | Yes | Yes | ||
| Moesch et al. (2013) | Early involvement in the main sport, often occurring in early to middle childhood, with very little or no involvement in other sports | Yes | Yes | Yes | |||
| Moesch et al. (2011) | Normally occurring in early to middle childhood, with little or no involvement in other sports. Additionally, the importance of a high amount of deliberate practice is stressed during all ages | Yes | Yes | Yes | Yes | ||
| Moseid et al. (2019) | The time when the athlete defined one sport as being more important than other sports | ||||||
| Mostafavifar et al. (2013) | Year-round sport-specific training, participation on multiple teams of the same sport and focused participation in a single sport | Yes | Yes | ||||
| Myer et al. (2015) | Intensive year-round training in a single sport at the exclusion of other sports | Yes | Yes | Yes | Yes | ||
| Myer et al. (2016) | Including year-round sport-specific training, participation on multiple teams of the same sport, and focused participation in a single sport | Yes | Yes | ||||
| NASPE Staff (2006) | None | ||||||
| Noble and Chapman (2018) | None | ||||||
| Normand et al. (2017) | Intense, year-round training program in a single sport at the exclusion of other activities | Yes | Yes | Yes | Yes | ||
| Padaki et al. (2017a) | Focusing on a sport to the exclusion of other sports and playing and training in the sport more than 8 months per year prior to the age of 12 | Yes | Yes | Yes | |||
| Padaki et al. (2017b) | The combination of playing and training in a single sport for > 8 months per year, playing a single sport “to the exclusion of participation in other sports,” and starting this commitment prior to age 12 years | Yes | Yes | Yes | |||
| Pantuosco-Hensch (2006) | Athletes limiting their participation to one sport which is practiced, trained for and/or competed in on a year round basis | Yes | Yes | ||||
| Pantuosco-Hensch (2010) | Athletes limit their athletic participation to one sport which is practiced, trained for, and competed in throughout the year | Yes | Yes | ||||
| Pasulka et al. (2017) | Year-long, intensive training in a single sport at the exclusion of other sports | Yes | Yes | Yes | Yes | ||
| Patel and Jayanthi (2018) | Intense, year-round training in a single sport with exclusion of other sports | Yes | Yes | Yes | Yes | ||
| Post et al. (2017c) | Year-round intensive training in a single sport at the exclusion of other sports | Yes | Yes | Yes | Yes | ||
| Post et al. (2017b) | Year-round participation in a single sport at the exclusion of other sports | Yes | Yes | Yes | |||
| Post et al. (2017a) | Year-round, intensive training in a single sport at the exclusion of other sports | Yes | Yes | Yes | Yes | ||
| Read et al. (2016) | As early age involvement in one chosen sport during the period of early-to middle childhood (up to age 13 years) with no subsequent participation in the other sports or activities available | Yes | Yes | Yes | |||
| Reider (2017) | Specializing in one sport to the exclusion of all others | Yes | Yes | ||||
| Rugg et al. (2018) | Intensive year-round training in a single sport at the exclusion of other sports | Yes | Yes | Yes | Yes | ||
| Russell (2014) | Limited their participation to one sport which they practiced trained and competed in year round | Yes | Yes | ||||
| Russell and Limle (2013) | Limited their participation to one sport which they practiced trained and competed in year-round | Yes | Yes | ||||
| Russell and Molina (2018) | Limited their participation to one sport, which was practices for and competed in throughout the year, to the exclusion of other activities | Yes | Yes | Yes | |||
| Santos et al. (2015) | These categories follows the guidelines of the Long-Term Athlete Development model | ||||||
| Santos et al. (2017) | Specialized participation in early childhood, promoting highly structured training as the answer to current competitive demands | Yes | |||||
| Sieghartsleitner et al. (2018) | Whether young talents should focus on a single sport specific domain early | Yes | Yes | ||||
| Sluder et al. (2017) | An athlete participating in a single main sport on a year-round basis (>8 months per year) and/or quitting all other sports to focus on a single sport | Yes | Yes | Yes | |||
| Smith (2015) | Limiting participation to one sport which is practiced, trained for and/or competed in on a year-round basis | Yes | Yes | ||||
| Smith et al. (2017) | None | ||||||
| Smucny et al. (2015) | Intensive, year-round training in a single sport at the exclusion of other sports | Yes | Yes | Yes | Yes | ||
| Stewart and Shroyer (2015) | None | ||||||
| Storm et al. (2012) | None | ||||||
| Strachan et al. (2009) | Investing at least 15 h per week in their respective sports and involved from a young age | Yes | |||||
| Sugimoto et al. (2019) | Year-around (more than 8 months per year) and quitting other sports in order to focus on one sport | Yes | Yes | Yes | |||
| Sugimoto et al. (2017) | Year-round, high-intensity training specialized to a single sport at an early age | Yes | Yes | Yes | Yes | ||
| Swindell et al. (2019) | Year-round training and participation in a single sport at the exclusion of other sports | Yes | Yes | Yes | |||
| Torres (2015) | A practice in which young athletes commit to train and compete almost exclusively in a single sport | Yes | Yes | ||||
| Waldron et al. (2019) | High intensity, year-round training in a single sport, with the exclusion of other sports | Yes | Yes | Yes | Yes | ||
| Wall and Côté (2007) | Intense training in one sport at a young age | Yes | Yes | Yes | |||
| Walters et al. (2018) | None | ||||||
| Weiss (2015) | None | ||||||
| Wiersma (2000) | Year-round training in a single sport at the exclusion of other sport or non-sport activities | Yes | Yes | Yes | |||
| Wilhelm et al. (2017) | Intense, year-round training in a single sport with the exclusion of other sports | Yes | Yes | Yes | Yes | ||
| Williams (2018) | Participation in a single sport and reporting more than 8 months per year training for that sport | Yes | |||||
| Wilson (2006) | Year-round training in a single sport at the exclusion of other activities | Yes | Yes | Yes | |||
| Zibung and Conzelmann (2013) | None | Yes | Yes |