Purpose: Soccer players frequently experience exercise-induced muscle damage (EIMD) due to the high-intensity, eccentric demands of training and match-play. This systematic review and meta-analysis aimed to quantify the pooled effect of soccer-specific exercise training on serum CK levels and to examine the moderating roles of post-exercise assessment timing (≤ 25 vs. > 25 hours), participant age (≤ 20 vs. > 20 years), and VO₂max (≤ 57 vs. > 57 mL/kg/min).
Method: A systematic search of PubMed/MEDLINE, Scopus, and Web of Science was conducted from inception to 2026. Twenty-nine eligible studies were included. Random-effects meta-analyses and subgroup analyses were performed.
Results: Exercise training significantly elevated CK levels (SMD = 0.553, 95% CI: 0.249 to 0.856; P = 0.001), with substantial heterogeneity (I² = 71.07%; τ² = 0.558). Subgroup analyses revealed that CK elevations were significant when measured within 25 hours post-exercise (SMD = 0.65, 95% CI: 0.27 to 1.04; P = 0.001) but not beyond 25 hours (SMD = 0.47, 95% CI: −0.06 to 0.99; P = 0.082). Younger players (≤ 20 years) demonstrated substantially larger effects (SMD = 1.26, 95% CI: 0.28 to 2.24; P = 0.012) compared to older players (> 20 years; SMD = 0.42, 95% CI: 0.13 to 0.70; P = 0.004). VO₂max showed the strongest moderating trend, with higher VO₂max (> 57 mL/kg/min; k = 5) associated with markedly larger CK elevations (SMD = 2.42, 95% CI: 0.61 to 4.24; P = 0.009) compared to lower VO₂max (≤ 57 mL/kg/min; SMD = 0.44, 95% CI: 0.16 to 0.72; P = 0.002), although this between-subgroup difference did not reach statistical significance (Q = 4.63, P = 0.099).
Conclusion: Soccer-specific training induces moderate-to-large CK elevations. VO₂max emerged as the most promising moderating factor and warrants further investigation with larger, well-controlled studies.