Objectives Investigating the effects of different training modes on the physical fitness of soccer players. Methods A comprehensive and systematic search was performed to identify studies that met the inclusion criteria, including randomized controlled trials (RCTs), with a cutoff date of November 2025. A random-effects network meta-analysis (NMA) was performed within a frequency-based framework. Results A total of 52 studies involving 1,320 participants were included. Regarding aerobic capacity, SUCRA rankings indicated that High-Intensity Interval Training (HIIT) had the highest probability of being the most effective intervention for improving VO2max levels (SUCRA = 74.3; SMD = 0.53, 95% CI [0.15, 0.91], p = 0.007). Regarding anaerobic capacity, HIIT ranked first for improving 20-m sprint test performance (SUCRA = 90.6; SMD = -0.51, 95% CI [-0.80, -0.22], p = 0.001), Change of direction (COD) (SUCRA = 81.2; SMD = -0.83, 95% CI [-1.22, -0.43], p < 0.001), and Repeated sprint ability (RSA) (SUCRA = 73.2; SMD = -0.94, 95% CI [-1.86, -0.03], p = 0.043). Low-intensity continuous training (LICT) presented the highest probability of effectiveness for the 30-m sprint test (SUCRA = 99.3; SMD = -1.26, 95% CI [-2.03, -0.50], p = 0.001) and Countermovement jump (CMJ) (SUCRA = 90.9; SMD = 0.96, 95% CI [0.16, 1.76], p = 0.019). Small-sided games (SSG) also yielded significant improvements in CMJ (SMD = 0.40, 95% CI [0.03, 0.77], p = 0.033) and COD (SMD = -0.51, 95% CI [-0.94, -0.09], p = 0.018). Notably, the HIIT + SSG group (HSG) was associated with a decrease in 20-m sprint test performance (SMD = 1.84, 95% CI [0.69, 2.99], p = 0.002). No training modality showed significant effects on 10-m sprint test performance. For soccer-specific endurance (SSE), HIIT emerged as the intervention with the highest probability of effectiveness for improving Yo-Yo Intermittent Recovery Test level 1 (Yo-Yo IR1) performance (SUCRA = 86.2; SMD = 0.78, 95% CI [0.33, 1.22], p = 0.001). Conclusions Current evidence indicates that HIIT presents the highest probability of effectiveness for enhancing soccer players` aerobic capacity and soccer-specific endurance (SSE). Furthermore, HIIT was associated with significant improvements across most indicators of anaerobic capacity. From a practical perspective, these findings suggest the potential value of integrating diverse training modalities in a personalized manner, tailored to specific objectives, to optimize physical fitness outcomes.
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