**2. Materials and Methods**

According to the purpose of the research, a search was performed in MEDLINE, PubMed, Scopus, the Directory of Open Access Journals and Science Direct databases; the keywords used included physical exercise, creatine supplementation, and oxidative stress. Our focus was on English articles published from 2008 to 2020. As shown in Figure 1, in the first stage, 341 articles were reviewed, and after removing duplicate articles and articles unrelated to the research objectives in several stages, 8 articles were selected for full study of their findings. After selecting articles and reviewing their findings on physical activity and creatine supplementation, information was collected focusing on the research objectives (Figure 1).

**Figure 1.** Flowchart of the study selection.
