# Effects of Resisted Methods upon Sprint Performance in Rugby Players: A Systematic Review
###### Abstract  
The resisted method can provide an effective way to improve sprinting in both the acceleration and maximal velocity phases. However, substantial discrepancies exist in the literature regarding the influence of the athletes' training status and the prescription of the load to be used in relation to the specific components of the desired sprint performance and its phases. The aim of this study was to carry out a systematic review of the research that analyzes the effects of the application of a sprint overload in rugby players, as well as to establish the results obtained in relation to the percentage of the load applied. For this purpose, the guidelines provided in the PRISMA Declaration were followed, and a search was conducted in five databases: PubMed, Web of Science, Psycinfo, Scopus, and SPORTDiscus. After screening, a total of 16 reports were included that met the proposed eligibility criteria. The results yielded information based on the effect of the application of an overload on the following aspects: (1) adaptation to training; (2) acute post-activation potentiation effect; and (3) acute effect and its influence on running kinematics and kinetics. It can be concluded that in order to work on weighted sprint training, the percentage of load to be used must be taken into account, as this percentage will determine to a large extent the effect that will be produced when it is applied. resistance training; resisted weighted training; resisted sprinting; acceleration; velocity; kinematics and kinetics +
Footnote †: journal: Medical  
In addition to being a determining factor, sprinting ability is a differentiating factor between players, and it has been shown that players with greater sprinting ability are more likely to progress to higher divisions, both at junior and senior levels [7]. Along these lines, recent studies indicate that athletes participating at higher competitive levels perform a greater number of sprints than athletes competing at lower levels [8]. Sprints are very present in rugby matches, often preceding decisive actions in the game [9]. According to [PERSON] et al. [2], elite rugby players, depending on their position, perform between 43 and 53 sprints on average per match, generally covering distances of less than 20 m and lasting less than 4 s. Very similar data are provided in studies with football players. [PERSON] et al. [10] analyzed, among other aspects, the number of sprints in a football match over a period of seven seasons in the English Premier League. The data showed an increasing proportion of actions of an explosive nature throughout the seasons studied, from 31 \(\pm\) 14 sprints per match (season 2006-07) to 57 \(\pm\) 20 (season 2012-13). On the other hand, [PERSON] et al. [11] examined the behavior of football players as a function of the trajectory of the sprint (linear sprint 17 m/ sprint in curve 17 m). They observed that a large number of the subjects (27 out of 45 subjects) showed higher performance in one direction of the race in the curve sprint than in the linear sprint, alluding that this could be due to the specificity of the test, since the curve sprint is usually more frequent than the linear sprint in football. It is clear, and this is demonstrated by a multitude of research, that improving the performance of velocity actions must pay special attention to the development of the ability to accelerate. Numerous methods have been investigated so far, as well as their combination, including unloaded sprint work, top and explosive strength training, and byometrics, and, as of today, no training method has re-emerged as a priority or as superior to others [12]. In relation to sprinting, [PERSON] et al. [13] distinguish two phases: on the one hand, the acceleration phase, and on the other hand, the maximal velocity phase. The acceleration starts from a practically static position and increases its velocity as the subject moves, while during the maximal velocity phase, the subject moves and increases its velocity of displacement.