ReviewHormonal Paper responses and combat sports https://doi.org/10.5114/biolsport.2018.71601 Hormonal responses to striking combat sports competition: a systematic review and meta-analysis 1 2 1 3 AUTHORS: Maamer Slimani , Armin Huso Paravlic , Helmi Chaabene , Philip Davis , Karim Corresponding author: Chamari4, Foued Cheour5 Maamer Slimani Research Laboratory “Sports Performance Optimization” 1 Research Laboratory “Sports Performance Optimization”, National Centre of Medicine and Science in Sports National Centre of Medicine (CNMSS), Tunis, Tunisia and Science in Sports (CNMSS) Tunis, Tunisia 2 Science and Research Centre, Institute for Kinesiology Research, Garibaldijeva 1, 6000 Koper, Slovenia Phone: + 216-97067695 3 Combat Sports Performance, Braintree, Essex, United Kingdom E-mail: [email protected] 4 Athlete Health and Performance Research Centre, ASPETAR, Qatar Orthopaedic and Sports Medicine Hospital, Doha, Qatar 5 Higher Institute of Applied Biology of Médenine, Medenine, Tunisia ABSTRACT: Striking combat sports are challenging, commonly stressing the endocrinological system based on a mixture of body-contact actions and physiological efforts. 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. Three electronic databases (i.e., PubMed, Google Scholar and ScienceDirect) were systematically searched (up to February 2016) followed by a manual search of retrieved papers. The data showed a moderate increase in cortisol (C) (ES = 0.79; 95% CI 0.31–1.28; p = 0.001), an extremely large increase in adrenaline (ES = 4.22; 95% CI 2.62–5.82; p < 0.001), and a very large increase in noradrenaline (ES = 3.40; 95% CI 1.03–5.76; p = 0.005) and human growth hormone (HGH) levels (ES = 3.69; 95% CI 1.96–5.42; p < 0.001) immediately following the combat events, compared to the control condition i.e., “pre-combat”. Furthermore, amateur athletes had a larger increase in C levels compared to highly trained athletes (ES = 2.91 [very large] vs ES = 0.56 [small]), while evening events showed greater alterations in C levels compared to morning events (ES = 1.91 [large] vs ES = 0.48 [small]), without significant differences between them (p = 0.26 and p = 0.06, respectively). The present meta-analysis also showed a small, insignificant increase in testosterone (T) (ES = 0.47 [small]; 95% CI -0.45–0.99; p = 0.074) and a decrease in insulin-like growth factor 1 levels (ES = -0.20 [trivial]; 95% CI -0.78–0.37; p = 0.486) immediately following the combat events, compared to the control condition. 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. Additionaly, sub-analysis results showed a significant difference between younger and older athletes (Q = 4.05, p = 0.044), suggesting that after combat, younger individuals (less than 17 years of age) had a small decrease in T levels (ES = -0.58), compared with the moderate increase observed in older individuals (ES = 0.76). In conclusion, irrespective of striking combat sports types, the results showed that both official and simulated bouts are a real stressor of the hormonal system of practitioners. Coaches and applied practitioners should adopt “pre-competitive cognitive/coping strategies” to improve the psychological state that mediates the hormonal changes-competition/outcome relationship of their athletes in order to mitigate athletes’ stress. Key words: Combat sports Competition Slimani M, Paravlic AH, Chaabene H et al. Hormonal responses to striking combat sports competition: CITATION: Stress a systematic review and meta-analysis. Biol Sport. 2018;35(2):121–136. Hormones Moderators Received: 2017-01-01; Reviewed: 2017-08-13; Re-submitted: 2017-08-23 Accepted: 2017-10-14; Published: 2017-11-23. Mediators INTRODUCTION Striking combat sports (i.e., karate, taekwondo, boxing and kickbox- taken and to monitor athletes’ stress per se. To date, many studies ing) are widely practised around the world [1-7]. Competition is the have examined physiological responses (e.g., heart rate, blood lactate) most remarkable stressor situation for the physiological, hormonal to karate [11,12], boxing [13] and kickboxing competitions [14-15] and psychological aspects of the individual [8-10]. However, there as a method to quantify the internal combat load. Furthermore, are several methods used by coaches and strength and conditioning evaluation of hormonal changes is also used to quantify the internal specialists to evaluate the internal and external combat loads under- combat load during striking combat sports competitions [16-18]. BIOLOGY OF SPORT, VOL. 35 NO2, 2018 121 Maamer Slimani et al. The acute endocrine/hormone response to exercise bouts, training thermore, a summary of the studies related to striking combat prac- and competition has received considerable attention in recent titioners would offer essential knowledge with regards to effectively years [16,19-23]. Particularly, the most widely used hormones to monitoring training load as well as the acute changes in stress-relat- quantify athletes’ stress per se during competitions are testosterone ed parameters, avoiding the development of non-functional over- (T) and cortisol (C). Testosterone is a steroid hormone secreted by reaching conditions or, the most importantly, overtraining syn- the Leydig cells of the testes under hypothalamic and pituitary con- drome [9,12]. In view of the non-consensual studies available in the trol defining the hypothalamo-pituitary-testicular (HPT) axis [23]. scientific literature, a systematic review and meta-analysis that pre- Testosterone has many physiological roles within the body, all of cisely summarize and investigate the effects of striking combat sports which can be placed into two categories: androgenic and anabol- on hormonal responses and the possible mediator/moderator variables ic [23]. Cortisol is also a steroid hormone, secreted by the adrenal that may interfere could help improving training and competition cortex via the hypothalamus-pituitary-adrenal (HPA) axis. It is known programme planning. Therefore, the aims of the present systematic as the regulator hormone of immune function and has a catabolic review and meta-analysis were to (a) discuss the hormonal respons- effect on tissue. It is also associated with a decrease in the activity es related to striking combat sports competition from the available of some anabolic hormones, such as insulin-like growth factor 1 scientific studies and (b) determine the moderator and mediator (IGF-1) and human growth hormone (HGH) [9]. High levels of C variables (i.e., self-efficacy, mood state, anxiety and motivation) in- could be associated with fatigue and inflammation, increasing the terfering in the hormone changes-competition relationship. risk of injury and indicating overtraining [22]. In addition, the tes- tosterone/cortisol (T/C) ratio has been considered as an accurate MATERIALS AND METHODS indicator of overtraining in athletes [22]. Accordingly, several studies 1. Search strategy have reported that striking combat sports competition is a very This review was conducted in accordance with Preferred Reporting high intensity and stressful activity that results in increased C Items for Systematic Reviews and Meta-analyses (PRISMA) Statement levels [5,16,24]. In contrast, the same consensus does not apply to guidelines [26] (Figure 1). A computerized search was performed in karate kata and kumite due to significant increases in glucose,T and PubMed, Google Scholar and ScienceDirect (up to February 2016) catecholamines levels, without significant changes in insulin and C for English-language, peer-reviewed investigations using the terms concentrations [17]. This controversy may be due to differences in “boxing”, “taekwondo”, “karate”, or “kickboxing” alone and together age, gender, and the nature of the competition. For instance, the with “hormonal response”, and “stress”. determination of moderator variables (i.e., which type of competition is most stressful) that influence the effect of competition on hor- 2. Inclusion and exclusion criteria monal responses is important to help coaches and strength and To be suitable for inclusion, studies had to fulfil the following selec- conditioning professionals adapt their training interventions to meet tion criteria: (a) non-randomized controlled trials (NRCTs); (b) stud- the needs of the athlete and to control these variables. ies focusing on striking combat sports with hormonal responses Performance in competitions and demanding work activities in- measurements (i.e., C, T, adrenaline, noradrenaline, IGF-1, and HGH); dicates that the concomitant measurement of hormonal and psycho- (c) studies containing healthy, amateur and elite participants practis- logical parameters offers a unique possibility to achieve a more ing striking competition; and (d) studies written in English. Studies comprehensive evaluation of the stress responses of the practitio- of older adults (age >60 years) were excluded. Also, reviews, com- ners [18,25]. In addition, previous studies have shown that compe- ments, interviews, letters, posters, book chapters, and books were tition events known to increase stress are associated with a higher also excluded. increase of C concentrations and