## 5 Discussion
(2018) [42] noted that a complex contrast training program caused a significant improvement in the RSA performance compared to a traditional strength program. The above-differences are likely due to the different programs of [PERSON] et al. (2018) [42], who had three strength training sessions for eight weeks, compared to the two of [PERSON] et al. [45; 46]. Moreover, [PERSON] et al. [42] used more than three exercises for the lower extremities (>3 in each workout) as opposed to [PERSON] et al. [44], who used only the half-squat exercise. As we understand, the volume of programs varies considerably. Moreover, the lack of significant differences in the RSA after the implementation of the strength program may be because the strength does not affect the important factors on which the RSA depends, such as aerobic capacity that helps in rehabilitation [55] and the increase in energy substrates (CP) necessary for repetitive sprints [56]. Studies examining SSG's effect on the RSA observed a significant improvement in it. The characteristics of the two studies differed quite a bit. More specifically, [PERSON] et al. (2018) [27] implemented a program for six weeks, 4 vs. 4 on a field, with a ratio of \(\sim\)75 m\({}^{2}\)/player, while [PERSON] et al. (2018) [29] implemented a program for eight weeks, 5 vs. 5 on a field, corresponding to 126 m\({}^{2}\)/player. The findings of these studies show that SSG can be used to improve RSA. As we can observe, they used small-player relationships of 4 vs. 4 and 5 vs. 5 and relatively large spaces of 78 m\({}^{2}\)/player and 126 m\({}^{2}\)/player. Finally, in the studies [47] where FIFA11+ was applied, no effect on the RSA was observed. It is well-known that this program (FIFA11+) was designed to prevent injuries to soccer players and not to affect physical abilities that are important for the RSA. The stimulus was not specific to the RSA, so the effectiveness was small. Of the thirteen specific studies, eight used an RSA program, three an anaerobic speed endurance and interval training and two studies used programs with resisted sprint. Of the studies that included RSA, only two [28; 36] did not observe any changes in the RSA\({}_{\text{meantime}}\). However, the study of [PERSON] et al. observed an improvement in the index of % RSA\({}_{\text{decrement}}\). In another study, [PERSON] et al. (2015) [28] used an RSA or an RSA and strength combination program. The lack of significant differences were justified by the authors as the possible fatigue of the athletes, as the study was carried out at the end of the racing season. The specialization of the training stimulus was important in improving the RSA regardless of the differences between the training programs. Of the three studies that used interval or anaerobic endurance training, only in the study of [PERSON] et al. (2015) [39] was there an improvement in the RSA. The difference in these studies is likely due to the participants. More specifically, all three studies implemented programs that affected the anaerobic-energy-production mechanism. Anaerobic training is known to increase the activity of anaerobic enzymes (e.g., phosphofructokinase, myokinase) [19], increases the expression of the Na\({}^{+}\), K\({}^{+}\) transport pump [57], increases the muscle glycogen content [19] and enhances muscle capillarization [58]. It is known that adults have better anaerobic adaptations than youths. In two studies, no differences were observed; the participants were adolescents. Finally, in the two studies carrying out programs involving resistance sprints, significant improvements in the ability of the RSA were observed. Reports show that resistance sprints can increase muscle capacity to store elastic energy and improve power output [59; 60; 61]. This can affect players' sprint performance, as it can improve the horizontal force and rate of force development [62]. In this review, the heterogeneity of intervention programs that were used for RSA improvement is obvious.