Table 1.

Summary of the studies included in the systematic review.

Study	Team Sport	Gender	N and Characteristics of the Sample	QS
Raab et al. [36]	Handball	Female and male	69 high-level players (M: n = 19; F: n = 10), medium-level (M: n = 13; F: n = 9), and low-level (M: n = 8; F: n = 10)	0.77
Vaeyens et al. [37]	Football	Male	n = 87, 13.0–15.8 yo (1)elite (n = 21; 14.7 ± 0.5 yo); (2)sub-elite (n = 21; 14.6 ± 0.3 yo); (3)regional (n = 23; 14.6 ± 0.6 yo) control group (n = 22; 14.5 ± 0.4 yo)	0.86
Den Hartigh et al. [38]	Football	Male	N = 88; 49 of them invited to practice at one of the five regional football schools, age: 10.91 ± 0.3 yo; and 39 non-invited, age: 10.55 ± 0.4 yo	0.73
Diaz del Campo et al. [39]	Football	Female and male	N = 129; from 7 to 14 yo; 55 high-level and 74 low-level players	0.77
French et al. [40]	Baseball	Female and male	N = 159; 28 of 7 yo; 44 of 8 yo; 45 of 9 yo; and 42 of 10 yo	0.68
Keller et al. [27]	Football	Male	N = 62; age: 17.0 ± 0.6 yo	0.77
Woods et al. [41]	Australian football	ND	N = 50; 25 talent-identified with 17.8 ± 0.5 yo; 25 non-talent-identified with 17.3 ± 0.6 yo	0.68
Bennett et al. [6]	Football	Male	N = 328 (n = 119, age = 12.1 ± 2.6 yo; n = 171, age = 13.2 ± 1.7 yo; n = 38, age = 14.2 ± 1.5 yo).	0.82
Raab et al. [42]	Handball	Female and male	54 (27 male and 27 female) handball players (age = 15.27 ± 1.65 yo) of different ability levels (high-level: n = 16; medium-level: n = 20; and low-level: n = 18).	0.73
Schorer et al. [43]	Handball	Male	(1)sub-youth (n = 8, 14.4 ± 0.5yo); (2)youth (n = 5, 16.8 ± 1.1yo); (3)junior (n = 9, 19.2 ± 1.6yo); (4)adult (n = 8, 27.3 ± 5.8yo), (5)senior (n = 3, 46.7 ± 3.8yo)	0.68
Sevil Serrano et al. [25]	Football	Male	N = 186; ages: between 8 and 19 yo	0.73
Gonçalves et al. [44]	Football	Male	N = 54; 18 players with 9.86 ± 0.2 yo; 18 players with 12.87 ± 0.2 yo; and 18 players with 14.89 ± 0.3 yo	0.73
Machado et al. [45]	Football	Male	N = 48; 24 with a 13.06 ± 1.5 yo; 24 with a 16.89 ± 0.1 yo	0.77
Musculus et al. [46]	Football	Male	N = 97; 48 younger, age: 8.76 ± 1.2 yo; 49 older, age: 12.18 ± 0.9 yo	0.77
González-Víllora et al. [47]	Football	Male	N = 57; 14 players with less than 8 yo; 13 players with less than 10 yo; 14 players with less than 12 yo; and 16 players with less than 14 yo	0.68
Gil-Arias et al. [48]	Volleyball	Female	N = 8; age: 14.75 ± 0.70 yo	0.86
Gil-Arias et al. [49]	Basketball	Male	N = 11; age: 12.7 ± 50.65 yo	0.86
Navarro et al. [50]	Football	Female	N = 20; age: 17.3 ± 2.8 y	0.82
Panchuk et al. [22]	Basketball	Female and male	N = 20; age: 17.0 ± 0.6 yo	0.82
Pizarro et al. [30]	Futsal	Male	N = 8; age: 15.38 ± 0.6 yo	0.77
Praxedes et al. [51]	Football	ND	N = 19; from which 10 average skill-level–age: 10.55 ± 0.5 yo and 9 low skill-level–age: 10.66 ± 0.5 yo	0.82
Praxedes et al. [52]	Football	Male	N = 19; experimental group had 10 players with 10.55 ± 0.5 yo and a control group with 9 players with 11.77 ± 0.7 yo	0.73
Praxedes et al. [29]	Football	ND	N = 19; age: 10.63 ± 0.5 yo	0.77
Romeas et al. [53]	Football	Male	N = 23; age: 21.67 ± 0.5 yo	0.73
Hohmann et al. [54]	Handball	Female and male	N = 20; age: born in 1993 N = 30; age: 14.89 ± 0.8 yo	0.77
Fortes et al. [55]	Volleyball	Male	N = 33; age: 16 ± 0.6 yo	0.86

QS: quality score; ND: not defined; yo: years old.