Eligibility Criteria
Articles were elected using criteria of Population-Intervention-Comparator-Outcomes-Study design (PICOS) (25) including: 1) healthy subjects received oral creatine supplementation, as a nutritional strategy; 2) original randomized-controlled trial researches; 3) reporting at least one measurement of muscle damage indices (creatine kinase (CK) and lactate dehydrogenase (LDH)); 4) provided muscle damage indices data as mean and standard deviation (SD) in both intervention and placebo groups. Also, criteria for exclusion were: 1) using a mixture of creatine in intervention group only (vitamins, Coenzyme Q10 and etc.); 2) semi experimental, trials without control groups and nonrandomized trials; 3) animal studies; 4) reviews and case reports