Behavior profile of cytokines submitted to combat sports. A systematic review

Introduction. - Combat sports trigger biological reactions responsible for altering plasma levels of pro and anti-inflammatory cytokines. Thus, although participation in moderate intensity activities can improve the immune function above sedentary levels, excessive and high intensity exercises can damage the immune system, requiring detection of a diagnostic nature in specific sporting scenarios, to enable the planning of adequate periodization. Objectives. - To synthesize and analyze the effects of combat sports on cytokine behavior; and provide quantitative estimates of the alterations in these markers. Methods. - The Embase, MEDLINE/PubMed, Central, Scielo, and SPORTDiscus databases were searched from the oldest records until May/2020. The search strategy included keywords related to the terms "cytokines'' and "combat sport''. To be included, studies were required to: (1) evaluate combat sports; (2) evaluate the behavior of cytokines in response to sport; and (3) have an observational design. The search and data extraction processes were carried out by two independent researchers, who followed a standardized form. Results. - In total, 11 studies (n = 189 participants, all male) met the inclusion criteria. The combat sports investigated in the studies included: wrestling, judo, karate, kick boxing, MMA, and boxing. With respect to the cytokines, the following were evaluated: IL-1, IL-2, IL-4, IL-5, IL-6, IL-8, IL-10, IL-13, IL-17, TNF-alpha and IFN. The outcomes demonstrated that there was an increase after exercise in TNF-alpha, IL-1, IL-6, IL-17, and IFN, whereas IL-8 and IL-10 demonstrated inconclusive outcomes, since the behavior of these cytokines was distinct between the studies. For IL-9, IL-2, IL-5, IL-4, and IL-13 the levels were not detectable. Conclusions. - The presented outcomes could be useful and relevant to understanding the necessary physiological demands in combat sports and enabled us to conclude that, regardless of the level of conditioning, volume, and modality practiced, there is a circumstance that indicates an acute level of stress in response to combat sports in men. (C) 2021 Elsevier Masson SAS. All rights reserved.