## 5 Discussion  
Soccer, as mentioned above, is an intermittent team sport where soccer players make \(\sim\)1200 cyclical changes in activity every 3 to 5 s. Many of these actions are sprints [48], indicating RSA's importance in high-level soccer. In recent years, more and more studies have been investigating the effect of specific programs on this capability [28; 39; 46], with most of them showing improvement after the implementation of the intervention program. As mentioned above, studies on soccer players were included in this review. Although there are several studies involving various sports, studies in soccer players are relatively limited (\(n=21\)), while research work on the effects of different training programs on RSA soccer players does not exist. The first separation of studies was made in relation to age in this study. Of the six studies carried out in adulthood, only [PERSON] et al. (2015) [28] did not notice an improvement in the RSA after the implementation of their intervention, while in five studies carried out on youth soccer players, there were no improvements in the performance of the RSA [38; 40; 45; 47]. In adult studies, performance improvement reached \(\sim\)9%, while in minors it reached \(\sim\)3%, although in any case, the ES ranged from trivial to large. These studies show that interventional programs cause less percentage improvement in youth soccer players. This may be related to the characteristics of the protocols (intensity, volume) chosen in each case. Moreover, this difference may be due to the characteristics of developmental ages. More specifically, the studies included in the review include participants from 11 to 17 years of age. It has been reported in previous studies that children in their preteens have reduced anaerobic capacity and their actions are more dependent on the aerobic-energy-production mechanism [49]. In this context, they show less lactic acid production and greater oxidation of fatty acids [50; 51] compared to adults. In addition, the level of biological maturation seems to affect the effectiveness of training [52; 53]. The above-reasons may influence the results of the studies. Concerning interventional programs, the studies were divided into those that applied sprint exercises (specific) and those that did not include sprint exercises (nonspecific). Of the specific studies (\(n=13\)), in only two were no improvement in RSA observed after the program implementation, while in nonspecific studies (\(n=8\)), no improvements were observed in three studies. Compared to the two categories, the percentage of studies where no effect occurred was \(\sim\)15% for the specific and \(\sim\)38% for the nonspecific. This observation may be due to the training principle of the specialization of the stimulus. Two methodologies are followed to improve the RSA. In the first, based on the above-principle of coaching, exercises are applied that include repeated sprints. The second method improves the individual factors that affect the performance of the RSA such as metabolic factors [54]. Of the nonspecific studies, two used pyometric programs, three used strength programs, two used SSG and one used the FIFA11+ program. Of the two studies using pyometric exercises, [PERSON] et al., (2016) [44] did not notice significant changes, as opposed to [PERSON] et al. (2020) [41]. Looking at the protocols they used, we find that [PERSON] et al. (2016) [44] applied high-intensity jumps, but the total volume of the program (-700 jumps) was almost half that of [PERSON] et al. (2020) [41] (-1300 jumps), which indicates that the volume of training can affect the effectiveness of the program, considering that the total workouts were 16 for both teams. Of the three studies that implemented strength programs, two were conducted by the same laboratory and implemented the same program without finding significant effects on the RSA [45; 46]. However, [PERSON] et al.