The Effects of Different Training Interventions on Soccer Players' Sprints and Changes of Direction: A Network Meta-Analysis of Randomized Controlled Trials  
[PERSON]  
1 Graduate School of Physical Education, Myongji University, Yongin 17058, Republic of Korea 1+
Footnote †: These authors contributed equally to this work. changing, jumping, turning, and other actions whilst playing the game [3,4]. Among them, straight sprinting is the most common action. From analyzing the movements of scoring players in soccer games, we know that straight sprinting and agility account for 51% of the total number of movements [5, 6, 7]. Compared to previous seasons, high-intensity running distance and actions have increased by 30% and 50%, respectively [8]. Sprinting and agility can be used to distinguish the level of an athlete, as has been shown in the studies in [4,9]. Soccer players' abilities such as sprinting and COD can be assessed through a variety of physical fitness tests (i.e., the 505 test and the linear speed 10 m test). These tests are inexpensive, easy to perform, and popular among coaches [10]. It should be highlighted here that agility is used to describe a \"rapid whole-body movement with a change of velocity or direction in response to a stimulus\", whereas COD is used to describe a pre-planned testing environment, whereby athletes change their movement direction and velocity without the inclusion of perceptual-cognitive processes [11]. To improve soccer players' performances in areas such as sprinting and agility, RCTs of different training interventions have been conducted. Good results have been obtained in strength training, pyometric training, speed-agility-quickness (SAQ) training, sled sprint training, and compound training [12, 13, 14, 15, 16]. In a previous systematic review and meta-analysis, the effect of strength training on the sprinting and jumping performance of professional soccer players was assessed [17]. Other studies have considered potential gender differences and different responses between men and women [8,18] and the effects of pyometric training on physical performance such as sprinting in male and female soccer players [19,20]. To find out which training method is the best, the effects of strength training and pyometric training on the sprinting, change of direction, and jumping performances of female soccer players were compared, and the effect of pyometric training was better than that of strength training [21]. When comparing the effects of sled sprint and vest-resistance sprint training on the sprint performance of young soccer players, sled sprint training was better [22]. In a comparison of the effects of weightlifting resistance training and pyometric training on players' speed abilities, the magnitude of the improvement was similar [23]. Moreover, for short sprint performance, [PERSON] et al. [24] divided training modes into three levels based on task specificity and primary (free sprint), secondary (resistance sprint, downhill assist sprint, etc. ), and tertiary (strength or pyometric training, etc.) training. However, there was no consistent conclusion as to how to improve soccer players' sprinting and agility abilities or which training method was the best. As far as we know, there have been no network meta-analyses comparing more than two training interventions. NMA is a relatively novel analysis method, which is different from a traditional meta-analysis. It combines the evidence of direct and indirect comparisons into a single analysis to compare the effects of two or more interventions [25]. It can be used to rank different interventions to inform the selection of an optimal training intervention [25]. Therefore, the purpose of this study was to perform a network meta-analysis to compare the effects of various training interventions using the results of previous RCTs and to derive the best interventions that relevant practitioners can refer to in selecting the most effective training.