Compare the Effect of Two Training Methods on the Interleukin-15 and Neutrophil Count in Young Athletes

 One of the methods that coaches use to simulate a real game is training or small sided games, and now the study of small sided games is one of the topics that has received the most attention of researchers active in soccer (3). Small sided games are defined as a smaller version of the official game, in which the trainers divide the playground into several small sided according to the training objectives (2). small sided games allow for increased individual participation and short-term physiological and immunological responses (4,5). However, little information is available on the effects of this type of training methods on physiological characteristics, including the immune responses of soccer players (6,7).
One of the cytokines involved in immunity is interleukin-15 (IL-15). Interleukin 15 is involved in the interaction and cooperation between adipose-muscle tissue and increases the metabolism of adipose tissue triglycerides and provides the resulting fatty acid to muscle fibers for consumption. On the other hand, this cytokine precipitates free fatty acid deposition, reduces adipose tissue and thus has potential role in weight control (10). On the other hand, some interleukins can increase the motility of neutrophils at the site of inflammation (14, 15). Neutrophils are among the axes of the innate human immune system, which according to available reports, their function is easily affected by the quality and quantity of physical activity (16).
small sided games are one of the training methods that can simulate the needs of racing (2). The importance of this type of training method is such that many coaches in the world often use it to simulate the physical, technical and tactical needs of a real soccer match (18), however, the impact of this type of training on the immune system and aspects Its physiological properties have received less attention. Examining the effects of this type of exercise on the immune system and especially the functional components of this system, including cytokines, can provide very effective information. There are contradictions in the research on the effect of exercise on IL-15, some of which have confirmed the acute effects of resistance training on this cytokine (11) and in another study, the lack of effect of endurance training on IL-15 has been reported (19). Therefore, in order to answer the ambiguities in this field, it is necessary to conduct various researches based on different variables such as the type, intensity and duration of training. On the other hand, a study that examines the effect of training in the field Small on IL-15 and neutrophils were not found. Therefore, the present study intends to compare the effect two modes of small sided games on the interleukin-15 and neutrophil levels in soccer players.

In this semi-experimental study, 24 youth soccer players of Tehran Province Premier League (15 to 18 years old) were selected and randomly divided into three groups include; control, 2 vs. 2 and 4 vs. 4. small sided game 2 vs. 2 consisted of eight two-minute activities with a minute of rest between each two minutes of play on a field measuring 20 by 25 meters. Also, the small sided game 4-on-4 included four four-minute activities with two minutes of rest after every four minutes on a field measuring 28 by 35 meters. Plasma levels of interleukin-15 and blood neutrophil counts were measured. Data were analyzed by t-test, One-way ANOVA and Tukey post hoc test at the P <0.05.

The results showed that IL-15 levels increased significantly only after small sided game 2 vs. 2 compared to before training (p=0.043). The number of neutrophils in both experimental groups increased significantly compared to before exercise (p=0.001). There was no significant difference in the number of neutrophils between the two experimental groups (p=1.000).

 The results of the present study showed that immediately after 2 vs. 2 in the small sided games, IL-15 levels increased significantly, although increase in IL-15 levels was also seen in exercise 4 vs. 4, but this increase, from the comment was not statistically significant. The findings of this study were consistent with the results of some Previous research showed that exercise leads to significant increase in IL-15 levels (11,20). Due to the fact that exercise training is performed in different intensities and will have different effects, according to the above, it can be suggested that one of the reasons for the difference between the effect of exercise 2 vs. 2 compared to 4 vs. 4 in contrast to IL-15, the intensity of exercise is high, which increases the response of interleukin-15 to exercise. No change or increase in IL-15 has been observed following exercise. These changes probably depend more than anything on the age and training status of the subjects. In any case, more research is needed and with only one research cannot be concluded with confidence. also, it has been suggested by Ajuwon and Spurlock (2004) that IL-15 may be produced by organs in response to immune stress in muscle protein stability and fat oxidation to produce energy (26). Therefore, the action of interleukin-15 on muscle mass and fat can be important for exercise. In the present study, small sided game 20-25 compared to small sided game 28-35 led to a further increase in interleukin-15 levels. In this regard, it has been shown that in a training session, there is strong inverse relationship between the reaction of interleukin-15 circulating to the intensity and duration of training, so that longer and less intense muscle activity can reduce the secretion of this myokine (11).  As mentioned, the intensity of training on small sided can be adjusted by changing or manipulating several factors, including the number of players involved in training, the size and shape of the small sided. Research has shown that training in small sided with fewer players increases heart rate more than training in small sided with more players (2).
Also, the results of the present study showed that exercise 2 vs. 2 and 4 vs. 4 increased the number of neutrophils, which is in line with the results of previous research (29,30). It is possible that the increase in neutrophil count is mainly due to exercise-induced muscle injury, but this increase has been seen following exercise that does not cause muscle damage (32). Also, some studies have shown that regular exercise reduces the number of neutrophils in active people (33). Because exercise can be considered a stress, and stress (both physical and mental) causes messages to be released from the brain and affect the functioning of the human immune system, the main neuroendocrine pathways against stress activated on the hypothalamic-pituitary-adrenal (HPA) axis, the human immune system controls the release of glucocorticoids (such as cortisol) and catecholamines. Thus, the primary increase in neutrophils is rooted in the release of catecholamines and the secondary increase is rooted in plasma cortisol activity (34). Overall, it seems that high intensity training on smaller pitches (Exercise 2 vs. 2 on 20-25m field) increased the IL-15 response. As mentioned, IL-15 is secreted by organs in response to immune stress in muscle protein stability and fat oxidation to produce energy. Therefore, the action of IL-15 on muscle mass and fat can be important for exercise. Therefore, it is recommended to use the game on smaller fields in order to have its benefits.