Distribution of training external and internal load throughout the week in soccer: A systematic review and Meta-Analysis

Abstract

Introduction: The manipulation of training loads (TL) is a fundamental objective in the optimization of sports performance in football, since it is closely associated with the player's performance and risk of injury. For this reason, the monitoring of external (EL) and internal training load (IL) is a common procedure in professional football, as it allows the characterization or stress experienced by players in training and games. As elite football players compete weekly, they can adjust the intensity and volume of training associated with the central importance of preparation for each game. Objective: The objectives of this systematic review were i) to describe the EL and IL to which the players are exposed during the competitive microcycle (training and game); ii) quantify the magnitude of the relationship between training and game load; and iii) calculate the magnitude of the relationship between the TL experienced at different moments of the microcycle (days typically considered for acquisition vs. recovery days vs. pre-game days). This review aims to answer these questions through a group (team) and individual analysis (according to the position of the players on the field). Methods: The bibliographic search was carried out in the PubMed, Scopus, EbscoHost and Web of Science databases, until the end of December 2019. The inclusion criteria were: i) professional male soccer players, over 18 years old, with regular participation in most training sessions (at least 80%) and with at least 45 minutes of playing time in each official match; ii) information available on the EL and IL during the training week and games, extracted in a period with a minimum duration of two weeks and with at least four training days before the game; iii) information about the mean and standard deviation or the possibility of its extraction from the figures; iv) non-congested training weeks (2 games per week); v) peer-reviewed journals published in English. Results: Thirteen studies were included (n = 251 players). The EL metrics, total distance (TD), very high speed running (VHSR) and sprint distance and IL metrics based on perceptual indices (Rating perception of effort; RPE) have been the most used indicators to characterize the TL during the competitive microcycle, both at group and individual level. During the microcycle, the TL gradually increases until M-4 and M-3 (96 and 72 hours before the game), then decreasing until day M-1 (24h before the game). The weekly load (sum of the different training sessions) referring to the TD, the high intensity running (HIR), high speed running (HSR) and the RPE showed to be higher than the performed during the game. However, the game values for VHSR and sprint distance were higher than the weekly training load. In the analysis of the individual TL in the different days of the microcycle, only differences were found in the TD covered between acquisition and pre-game training units (e.g. M-3 vs. M-1). Conclusion: The soccer game is a fundamental stimulus for the maintenance / improvement of the player's ability to perform very high intensity activities. Regarding the analysis of the different training sessions, the training carried out 72 hours before the game (M-3) seems to be the training in which higher EL values are examined (e.g. TD, VHSR, decelerationhigh). In subsequent training sessions, there is a decrease in the TL (M-2 and M-1) until the game day, especially on the day before the game (M-1). However, about the parameters VHSR and sprint distance, the values accumulated in all training sessions training cycle did not reach the values recorded in the game (97% and 91%, respectively).