A computerized search was performed in PubMed, Google Scholar and ScienceDirect (up to February 2016) for English-language, peer-reviewed investigations using the terms "boxing", "taekwondo", "karate", or "kickboxing" alone and together with "hormonal response", and "stress". Particularly, the most widely used hormones to quantify athletes’ stress per se during competitions are testosterone (T) and cortisol (C). Furthermore, evaluation of hormonal changes is also used to quantify the internal combat load during striking combat sports competitions 16-18. Striking combat sports (i.e., karate, taekwondo, boxing and kickboxing) are widely practised around the world 1-7. The greatest increase of the bloodstream levels of noradrenaline concentration in karate could indicate a higher level of aggression in karate. However, further studies are necessary to draw binding conclusions on the contribution of the emotional load of specific combat sport disciplines to the hormonal response. On the other hand, the increase of the blood cortisol level following competition was similar in all groups analyzed. The karate fighters studied here had the highest levels of hormones related to aggressive behavior; in contrast, earlier data on Polish sportsmen indicated that karate athletes were the least aggressive group compared to boxers, ju-jitsu fighters, and nontraining subjects . Furthermore, when comparing the stress response between genders after an official taekwondo competition, male athletes show higher absolute values, but a smaller increase (73%) between pre-bout and peak sC values than their female counterparts (199%) . From the quantitative studies, four studies examined the C responses to striking combat sports competitions; four studies investigated the T response; two studies assessed the adrenaline and noradrenaline responses; one study assessed the IGF-1 response; and finally one study measured the HGH response. Additionally, a meta-regression was also performed to examine whether the age of athletes may predict alterations in C and T levels following striking combat sports events/competitions. This study is the first one to compare the hormonal response to competition in different combat sports. Performance in competitions and demanding work activities indicates that the concomitant measurement of hormonal and psychological parameters offers a unique possibility to achieve a more comprehensive evaluation of the stress responses of the practitioners 18,25. The type of combat sports practised, participants’ gender, and the nature of competition contests (i.e., official vs simulation) did not moderate the relationship between competition and hormonal response. The aims of this systematic review and meta-analysis were to discuss the hormonal responses related to striking combat sports competitions and to investigate the moderator and mediator variables of the hormonal response-competition/outcome relationship. These data provide sufficient ground to conclude that there are no fundamental differences in the physical capacity among athletes from various combat sports. The requirements for sports with marking techniques, with karate and partly taekwondo being examples, are different than for a real physical contact fight (e.g., judo, kick-boxing, and wrestling). So, in sports which involve kata and faking techniques, the athletes show lower preparedness to a real physical struggle with an opponent than do athletes in other combat sport disciplines . Most karate and taekwondo competition involves predesigned attack, defense, and counterattack (kata) demonstration forms. Another study showed that Polish wrestlers were more aggressive than karate fighters. Litwic-Kamińska suggests that taekwondo and judo athletes from the Polish population are characterized by high resiliency, which makes them more resistant to stress. It seems likely that differences in the increase of noradrenaline level between the groups do not reflect the physical load of the exercise itself but rather the different emotional engagement/aggression levels in the respective disciplines. These hormonal changes reflect the neuroendocrine adaptation to competition-related exercise as well as aggression level and cognitive functioning. We found a rise in the blood BDNF level following the fight, similar for all the combat sport disciplines studied. To the best of our knowledge, our study is the first to investigate the effect of a short but very intense exercise during a combat sport fight on BDNF concentration. In this paper, the T/C indices were similar in all groups, which indicates a similar physical load in all combat sports analyzed.
