Table 2. Characteristics of included studies (n = 29). Data extracted from included RCTs. Study (Year) n Age Sex Intervention Tier Duration Sessions Barra-Moura (2024) 21 15.3 ± 1.1 M/F CBT vs TST Tier 2 6weeks 3 Dhull (2025) 30 22.9 ± 1.5 M CBT vs TST Tier 3 4weeks 2 Gallego-Sendarrubias (2021) 24 25.5 ± 4.2 M CBT vs STG Tier 3 2weeks 2 Gómez (2023) 21 21.2 ± 3.0 M CBT vs HIIT Tier 3 4weeks 2 Liu (2024) 51 16.3 ± 0.6 M PT vs CBT Tier 2 8weeks 4 Nonnato (2022) 16 23.0 ± 4.0 F PT vs TST Tier 3 12weeks 4 Quan (2024) 21 17.7 ± 1.7 M CBT vs TST Tier 2 4weeks 2 Sagelv (2020) 38 23.2 ± 2.6 M FT vs STG Tier 3 6weeks 2 Sammoud (2024) 27 12.3 ± 0.5 M PT vs TST Tier 2 8weeks 2 Yang (2025) 45 15.7 ± 0.5 F PT vs TST Tier 2 6weeks 2 Zhu (2025) 46 16.5 ± 0.5 M PT vs TST Tier 2 6weeks 2 Brahim (2025) 32 19.1 ± 0.7 M FT vs STG Tier 3 8weeks 2 Sedano Campo (2009) 20 22.9 ± 2.7 F PT vs STG Tier 3 12weeks 3 Fischetti (2019) 28 26.6 ± 6.1 F PT vs TST Tier 3 12weeks 3 Maciejczyk (2021) 15 19.6 ± 2.4 F STG vs TST Tier 3 4weeks 2 Ozbar (2014) 18 18.2 ± 2.3 F PT vs TST Tier 2 8weeks 1~3 Sperlich (2011) 17 13.5 ± 0.4 M HIIT vs TST Tier 3 5weeks 3~4 Ferrari Bravo (2008) 26 21.1 ± 5.1 M HIIT vs TST Tier 3 7weeks 2 Mujika (2009) 20 18.3 ± 0.6 M HIIT vs STG Tier 3 7weeks 1 Tønnessen (2011) 20 16.4 ± 0.9 M HIIT vs TST Tier 3 10weeks 1 Pecci (2023) 20 20.5 ± 2.6 F PT vs TST Tier 3 6weeks 2 Sanchez-Sanchez (2019) 22 22.5 ± 2.2 M HIIT vs FT Tier 2 5weeks 2 Buchheit (2010) 15 14.5 ± 0.5 M HIIT vs PT Tier 3 10weeks 1 Los Arcos (2015) 15 15.5 ± 0.6 M HIIT vs TST Tier 2 6weeks 2 Hammami (2019) 40 15.9 ± 0.3 M CBT vs PT Tier 2 8weeks 4~5 McKinlay (2018) 41 12.5 ± 0.6 M STG vs PT Tier 2 8weeks 3 Vera-Assaoka (2020) 76 13.0 ± 1.5 M PT vs TST Tier 2 7weeks 2 de Hoyo (2015) 33 17.5 ± 1.0 M FT vs TST Tier 3 10weeks 1~2 Coratella (2019) 40 23.0 ± 4.0 M FT vs STG Tier 3 8weeks 1 Note: Tier classification followed the Participant Classification Framework Tier 1 = recreationally active, Tier 2 = trained/developmental, Tier 3 = highly trained/national level. Youth players were defined as ≤18 years, whereas adult players were defined as >18 years. TST: Traditional soccer training, FT: Flywheel Resistance Training, STG: Traditional Strength Training, PT, Plyometric Training, CBT, Combined Training, SSG: Small-Sided Games Training, RST: Repeated Sprint Training, HIIT: High-Intensity Interval Training. The intervention column presents the direct comparison evaluated in each study. Duration = intervention period in weeks; Frequency = number of training sessions per week.