Supplementary Table S2. Characteristics of the studies included in the meta-analysis. Author Country Year Age (mean ± SD) Sample size (test group / control group) Intervention Details Control Outcome Gao F. China 2023 19.3 ± 3.5 15/15 10 weeks Speed Training Regular Training 30 m sprint Little T. UK 2006 24 ± 3 18/18 3 times/week Flexibility Training Regular Training 20 m sprint COD test Sayers A.L. USA 2008 19.35 ± 0.99 20/20 1 week Flexibility Training Regular Training 30 m sprint Sánchez-Sánchez J. Spain 2024 22.9 ± 3.5 10/13 16 weeks Plyometric Jump Training Regular Training CMJ test COD test Hostrup M. Denmark 2019 22.8 ± 2.2 12/10 10 weeks, 3 times/week Endurance Training Speed Training 30 m sprint Nobari H. Iran 2023 23.1 ± 2.8 10/9 13 weeks Speed Training Plyometric Jump Training 20 m sprint, 30 m sprint COD test Wallenta C. Germany 2016 18.3 ± 2.0 6/6 6 weeks, 2 times/week Speed Training Traditional Strength Training CMJ test 5 m sprint Rønnestad B.R. Norway 2011 22 ± 2 7/7 10 weeks, 2 times/week Traditional Strength Training Regular Training 40 m sprint 1RM test Rønnestad B.R. Norway 2006 23 ± 2 6/7 7 weeks, 2 times/week Traditional Strength Training Regular Training 1RM test, SJ test, CMJ test 30 m sprint Rey E. Spain 2016 23.6 ± 2.7 10/9 6 weeks, 2 times/week Traditional Strength Training Speed Training CMJ test 30 m sprint López-Segovia M. Spain 2010 18.43 ± 0.6 19/18 16 weeks, 4 times/week Traditional Strength Training Regular Training CMJ test, 20 m sprint 30 m sprint Moran J. UK 2024 22.3 ± 2.7 8/8 8 weeks, 2 times/week Speed Training Regular Training CMJ test COD test Gee T.I. UK 2021 17.1 ± 0.6 9/8 10 weeks, 2 times/week Traditional Strength Training Speed Training 40 m sprint COD test Pareja-Blanco F. Spain 2017 23.8 ± 3.5 8/8 6 weeks, 3 times/week Traditional Strength Training Regular Training 1RM test, CMJ test 30 m sprint Loturco I. Brazil 2015 23.4 ± 3.6 12/11 4 weeks, 2 times/week Speed Training Plyometric Jump Training SJ test, 5 m sprint 20 m sprint Loturco I. Brazil 2017 21.7 ± 2.4 11/11 5 weeks, 2 times/week Speed Training Plyometric Jump Training 5 m sprint, 20 m sprint 30 m sprint, COD test SJ test, CMJ test Iaia F.M. Italy 2015 18.5 ± 1 6/7 3 weeks, 3 times/week Speed Training Endurance Training 20 m sprint 40 m sprint Enright K. UK 2015 17 ± 2 8/7 5 weeks, 2 times/week Traditional Strength Training Endurance Training 1RM test, SJ test CMJ test Kobal R. Brazil 2017 18.9 ± 0.6 9/9 8 weeks, 2 times/week Traditional Strength Training Speed Training CMJ test, 20 m sprint COD test Soares-Caldeira L.F. Brazil 2014 22.6 ± 6.7 6/7 4 weeks, 2 times/week Speed Training Regular Training SJ test CMJ test Keiner M. Germany 2022 17.45 ± 0.52 11/11 40 weeks, 2 times/week Traditional Strength Training Speed Training 1RM test, 20 m sprint COD test Milanović Z. Serbia 2014 18.5 ± 0.4 66/66 12 weeks, 4 times/week Speed Training Regular Training 20 m sprint Chelly M.S. Tunisia 2010 19.1 ± 0.7 12/11 8 weeks, 2 times/week Speed Training Regular Training SJ test CMJ test Bettariga F. Italy 2022 25.4 ± 4.9 12/12 6 weeks, 2 times/week Plyometric Jump Training Regular Training 5 m sprint, 20 m sprint 30 m sprint Silva-Neto M.E. Brazil 2023 19 ± 0.8 12/12 2 weeks Flexibility Training Traditional Strength Training CMJ test 30 m sprint Dupont G. France 2004 20.2 ± 0.7 22/22 10 weeks Speed Training Regular Training 40 m sprint McMorrow B.J. Ireland 2019 24.0 ± 3.6 7/6 6 weeks, 1–2 times/week Speed Training Traditional Strength Training 5 m sprint, 20 m sprint COD test Hammami M. Tunisia 2020 16.4 ± 0.2 14/12 10 weeks, 2 times/week Plyometric Jump Training Regular Training 5 m sprint, 20 m sprint 30 m sprint, 40 m sprint COD test, SJ test, CMJ test Hammami M. Tunisia 2018 16.1 ± 0.5 14/12 8 weeks, 2 times/week Traditional Strength Training Regular Training SJ test, CMJ test, COD test, 1RM test 5 m sprint, 40 m sprint Hammami M. Tunisia 2018 16.8 ± 0.2 16/12 8 weeks, 2 times/week Traditional Strength Training Regular Training COD test, SJ test, CMJ test, 1RM test 5 m sprint, 20 m sprint 30 m sprint, 40 m sprint Hammami M. Tunisia 2017 16.2 ± 0.6 19/12 8 weeks, 2 times/week Traditional Strength Training Regular Training COD test, SJ test, CMJ test, 1RM test 5 m sprint, 20 m sprint 30 m sprint, 40 m sprint Participants in all studies were soccer players. Data are presented as mean ± standard deviation (SD). Intervention Details specify the duration and weekly frequency of the training programs. Intervention and Control groups are categorized according to the specific nodes used in the network meta-analysis: Traditional Strength Training (high-load resistance), Plyometric Jump Training (ballistic/jump exercises), Speed Training, Endurance Training, Flexibility Training, and Regular Training. Outcomes include linear sprint times (5-40 m), vertical jump height (SJ = Squat Jump; CMJ = Countermovement Jump), maximal strength (1RM = One-Repetition Maximum), and change of direction ability (COD).