Background This study aims to investigate how accumulated training load over different time windows (7, 14, and 28 days) influences the incidence of hamstring injuries in elite football players. Methods A descriptive and longitudinal study was developed in 343 players in three teams (2nd Team, U-19 team, and U-18 team) from the academy of an elite football club in Spanish La Liga that also competed in the Union of European Football Associations Champions League during four seasons, from 2017/18 to 2020/21. External load variables (total distance, high-speed running, accelerations, etc.) for training and competition have been studied considering the volume variables during three different time windows along the different seasons (7 days, 14 days, and 28 days). Results Results did not show differences in the shortest time windows (7- and 14-week periods), showing that strength and conditioning coaches should analyse longer periods of time and compare them to previous periods with the same length in order to improve workload management and reduce injury risk. Conclusions It is important consider the accumulated load (chronic) in periods of 28 days to avoid an increase that generates a hamstring injury. The control of the training load in blocks of 28-day time windows seems essential to minimize the injury rate in football players.
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