Table 5. Study design and sample characteristics.

Author (date)	Country	Study design	Participants			Intervention			Maturity assessment
			N (sex)	Age (years)	Competitive Level	Compared groups	Type	Duration
Abbott et al. (2019)	UK	Repeated-measures crossover	25 M	12.7 ± 1.0	Soccer academy players	BB vs. CA	11v11	4 x 20 min 2 matches (1 CA + 1 BB)	Khamis–Roche (1994) method
Arede et al. (2024)	Portugal	Repeated-measures crossover	116 M	U13: 12.2±0.3 U14:13.2±0.4	Soccer academy players	BB vs. CA	7v7	20 min 8 matches (4 CA + 4 BB)	Khamis–Roche (1994) method
Lüdin et al. (2022)	Switzerland	Randomized cross-over repeated	65 M	11.7-13.7	Elite youth soccer clubs players	BB vs. CA	9v9	2 x 35 min 2 matches (1 CA + 1 BB)	Mirwald et al. (2002) method
Romann et al. (2020)	Switzerland	Repeated-measures crossover	60 M, 2 F	U13: 12.2±0.3 U14: 13.2±0.4	Elite youth soccer clubs players	BB vs. CA	9v9	20 min 8 matches (4 CA + 4 BB)	Mirwald et al. (2002) method
Towlson et al. (2021a)	UK	Repeated measures	32 M	12.9 ± 0.9	Soccer academy players	BB vs. MM	4v4 SSGs	5 min, 96 matches (48 MM + 48 BB)	Khamis–Roche (1994) method
Towlson et al. (2021b)	UK	Repeated measures	72 M	11-14	Soccer academy players	BB vs. MM	4v4 SSGs	5 min, 15 matches (5 MM + 10 BB)	Khamis–Roche (1994) method; Fransen et al. (2018) method
Towlson et al. (2022)	UK	Repeated measures	72 M	11-14	Soccer academy players	BB vs. MM	4v4 SSGs	5 min 15 matches (5 MM + 10 BB)	Khamis–Roche (1994) method; Fransen et al. (2018) method
Salter et al. (2023)	UK	Repeated measures	55 M	13.8 ± 1.4	Soccer academy players	BB vs. CA	6v6 SSGs,	5 min 30 matches (15 CA + 15 BB)	Khamis–Roche (1994) method
Salter et al. (2025)	UK	Repeated-measures crossover	139 M	12-16	Junior Premier League players	BB vs. CA	11v11	20 min 6 matches (3 CA + 3 BB)	Khamis–Roche (1994) method
King et al. (2025)	UK	Cross-sectional repeated-measures	53 M	13.4 ± 0.9	Soccer academy players	BB vs. MM	4v4, 5v5, and 6v6 SSGs	5 min 72 matches (36 MM + 36 BB)	Fransen et al. (2018) method
Robinson et al. (2025)	UK	Cross-sectional repeated-measures	118 M	13.7 ± 0.8	Junior Premier League players	BB vs. CA	11v11	20 min 6 matches (3 CA + 3 BB)	Khamis–Roche (1994) method
De Macedo et al. (2025)	Brazil	Repeated measures	20 M	11.8 ± 1.15	Soccer academy players	BB vs. CA	5v5 SSGs	4 x 5 min 6 matches (2 CA + 4 BB)	Mirwald et al. (2002) method
Barrett et al. (2022)	UK	Repeated measures	32 M	12.9 ± 0.9	Soccer academy players	BB vs. MM	4v4 SSGs	5 min 12 matches (6 CA + 6 BB)	Khamis–Roche (1994) method

Abbreviations: N, number; M, male; F, female; BB, Bio-banded; CA, chronological age; MM, Mixed-maturity (surrogate control); SSGs, small-sided games.