Effects of creatine supplementation on serum CK concentration
According to our analysis on 25 trials, in overall, creatine consumption had significant effect on CK concentration: (WMD = -30.94; 95% CI: -53.19, -8.69; P = 0.006). There was significant heterogeneity among the articles (P = 0.000, I2 = 99.8 %) (Figure 2) . Subgroup analysis was coducted to investigate if the effect of creatine supplementation on serum CK is different according to follow-ups after exercise, dose of creatine, duration of studies and train status (Figure 2 and Table 3 ). Some of subgroup analysis showed that creatine consumption resulted in a significant reduction in CK concentrations in trials with 48, 72 and 96 hours measurement of CK after exercise, >20 g/day creatine consumption, ≤1 trial duration and studies on untrained participant.