Introduction
It is well known that various types of exercise induce muscle damage. Exercise-induced muscle damage (EIMD) is recognized as the outcome of intense to moderate physical activity (1, 2). This damage manifests itself as a temporary decrease muscle function, increases in serum creatine kinase (CK) and lactate dehydrogenase (LDH) concentrations, increases in myoglobin and delayed onset muscle soreness (DOMS) (3). The basic feature of skeletal muscle damage without cell necrosis is the muscle fiber disruptions, chiefly the basal lamina sheath. Regarding mechanical stimuli, especially intense physical activity, it is understood that it can increase micro damage in muscle fibers imposed by eccentric contractions, according to the volume and length the damage degree and DOMS may be persist chronically over time (4, 5). The symptoms of DOMS which include muscle pain, strength loss, tenderness, swelling and stiffness have been suggested to happen within 24 hours of muscle damage and last beyond five days (6). Degradation of contractile proteins appears to relate to reduces in muscular force about one week to one month after eccentric exercise (7). Due to EIMD and DOMS that follows intense, unaccustomed or eccentrically biased exercise, a focus on recovery strategies that attenuate these unwanted effects should be pursued. Recently, some studies indicated that creatine consumptin might reduce post-exercise muscle damage via mechanisms regulating mitochondrial permeability and stabilizing the sarcolemma (8-10).
Newly, many athletes have consumed ergogenic aids to enhancing recovery, maintain body conditioning and physiological adaptations during long-term exercise programmes. Thus, the efficacy of ergogenic aids has always attracted great attention, and many researchers have sought to combine exercise training programmes and ergogenic aid to reinforce the benefits of exercise (11, 12). Creatine is a popular and favorite ergogenic aid at all levels among athletes that is synthesized endogenously from the amino acids glycine, methionine and arginine or intaked from the diet (8, 13). Articles studing the creatine supplementation effects have demonstrated improved performance in various exercise under a variety of different testing situation (14, 15) , although this has not been shown in all studies (16, 17). Theoretically, enhancing the availability of phosphocreatine would augment cellular bioenergetics of the phosphagen system (18, 19) in addition to the high-energy phosphates shuttling between the cytosol and mitochondria via the creatine phosphate shuttle (20). Also, there is evidence that supplementation with creatine may provide benefits for patients with diversity of neuromuscular diseases (21, 22) and metabolic disorders (23, 24). These results have showed that creatine supplementation may provides a ergogenic aid for individuals and also may present some therapeutic advantage for special populations.
In this regard, all related articles have been gathered in this study and as far as the studies quality allows and the creatine effects on EIMD have been evaluated. This systematic review and meta-analysis summarizes a detailed analysis about the hypothesis that creatine consumption can ameliorate EIMD and DOMS.